[Federal Register Volume 77, Number 169 (Thursday, August 30, 2012)]
[Proposed Rules]
[Pages 52650-52673]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-21352]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R6-ES-2012-0040; 4500030113]
Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition To List the Platte River Caddisfly as Endangered or
Threatened
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of 12-month petition finding.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a
12-month finding on a petition to list the Platte River caddisfly
(Ironoquia plattensis) as an endangered or threatened species and to
designate critical habitat under the Endangered Species Act of 1973, as
amended. After review of all available scientific and commercial
information, we find that listing the Platte River caddisfly as an
endangered or threatened species is not warranted at this time.
However, we ask the public to submit to us any new information that
becomes available concerning the threats to the Platte River caddisfly
or its habitat at any time.
DATES: The finding announced in this document was made on August 30,
2012.
ADDRESSES: This finding is available on the Internet at http://www.regulations.gov at Docket Number FWS-R6-ES-2012-0040. Supporting
documentation we used in preparing this finding is available for public
inspection, by appointment, during normal business hours at the U.S.
Fish and Wildlife Service, Nebraska Field
[[Page 52651]]
Office, Federal Building, 2nd Floor, 203 West 2nd Street, Grand Island,
NE 68801. Please submit any new information, materials, comments, or
questions concerning this finding to the above street address.
FOR FURTHER INFORMATION CONTACT: Michael D. George, Field Supervisor,
Nebraska Field Office (see ADDRESSES); by telephone (308-382-6468,
extension 12); or by facsimile (308-384-8835). mail to: Persons who use
a telecommunications device for the deaf (TDD) may call the Federal
Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Background
Section 4(b)(3)(B) of the Endangered Species Act of 1973, as
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition
to revise the Federal Lists of Endangered and Threatened Wildlife and
Plants that contains substantial scientific or commercial information
that listing a species may be warranted, we make a finding within 12
months of the date of receipt of the petition. In this finding, we will
determine that the petitioned action is: (1) Not warranted, (2)
warranted, or (3) warranted, but the immediate proposal of a regulation
implementing the petitioned action is precluded by other pending
proposals to determine whether species are either an endangered or
threatened species, and expeditious progress is being made to add or
remove qualified species from the Federal Lists of Endangered and
Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act requires
that we treat a petition for which the requested action is found to be
warranted but precluded as though resubmitted on the date of such
finding, that is, requiring a subsequent finding to be made within 12
months. We must publish these 12-month findings in the Federal
Register.
Previous Federal Actions
On July 30, 2007, we received a petition dated July 24, 2007, from
Forest Guardians (now WildEarth Guardians), requesting that 206 species
in the Mountain-Prairie Region, including the Platte River caddisfly,
be listed as an endangered or threatened species under the Act, and
critical habitat be designated. Included in the petition were analyses,
references, and documentation provided by NatureServe in its online
database at http://www.natureserve.org/. We acknowledged receipt of the
petition in a letter to the petitioners, dated August 24, 2007, and
stated that, based on preliminary review, we found no compelling
evidence to support an emergency listing for any of the species covered
by the petition. In that letter we also stated that we would begin to
assess the information provided in the petition in October 2007.
We published a partial 90-day finding for 38 of the petition's 206
species in the Federal Register (74 FR 41649) on August 18, 2009; the
Platte River caddisfly was one of 29 species for which we found there
was substantial information indicating that listing may be warranted
under the Act. In that document, we announced that we were initiating a
status review. On January 12, 2010, WildEarth Guardians filed a
complaint indicating that the Service failed to comply with the
statutory deadline to complete a 12-month finding for the Platte River
caddisfly. This complaint was consolidated with several others, and a
multi-district settlement agreement with WildEarth Guardians was
approved on September 9, 2011, which included an agreement that the
Service would complete the 12-month finding for the Platte River
caddisfly by the end of Fiscal Year 2012. Funding for completing the
12-month finding became available in Fiscal Year 2011, and we began
work at that time. This notice constitutes the 12-month finding on the
July 24, 2007, petition to list the Platte River caddisfly as an
endangered or threatened species.
Species Information
Species Description
The Platte River caddisfly (Ironoquia plattensis) adult is a small,
brown, moth-like insect with a body length of 5.5-6.5 millimeters (mm)
(0.21-0.26 inches (in)) and forewing length of 6.5-8.0 mm (0.26-0.31
in) (Alexander and Whiles 2000, p. 2). Wing membranes and veins are
light or iridescent brown with white spotting (Alexander and Whiles
2000, p. 2). The Platte River caddisfly has a short proboscis (tubular
mouthpart used for feeding) and long antennae, similar to other species
of caddisflies (Holzenthal et al. 2007, p. 648). Platte River caddisfly
adults can be distinguished from those of other species in the
Ironoquia genus by their much smaller size (forewing length of 6.5-8.0
mm (0.26-0.31 in) in Platte River caddisflies contrasting with >14 mm
(0.55 in) in most other Ironoquia species) (Alexander and Whiles 2000,
p. 2).
Like several caddisfly species, Platte River caddisfly larvae
construct a case around the abdomen (Mackay and Wiggins 1979, p. 186).
All caddisflies produce silk from modified salivary glands, and case-
making caddisfly larvae use this silk to fuse together organic or
mineral material from the surrounding environment (Mackay and Wiggins
1979, pp. 185-186; Holzenthal et al. 2007, p. 644). Cases are generally
thought to protect larvae by providing camouflage against predation or
resistance to crushing (Mackay and Wiggins 1979, p. 200; Otto and
Svensson 1980, p. 855). The Platte River caddisfly case is composed of
sand grains and can be up to 16.0 mm (0.63 in) long, while larvae can
attain sizes up to 14.0 mm (0.55 in) in length (Vivian 2010, pers.
obs.).
Platte River caddisfly larvae have a light brown head and thorax
and a yellowish to whitish abdomen (Vivian 2010, pers. obs.), much like
the larvae of Ironoquia parvula (no common name) (Flint 1958, p. 59).
Larvae in the Ironoquia genus can be distinguished from larvae in other
caddisfly genera by four morphological characteristics that are
distinguishable under a microscope (Flint 1958, p. 59; Wiggins 1977, p.
248). Differences in larval size (Alexander and Whiles 2000, p. 1) and
case material among species have also been noted (Wiggins 1977, p.
248).
Taxonomy
The Platte River caddisfly was formally described as a new species
in the order Trichoptera (caddisflies) in 2000 by Alexander and Whiles
(2000, p. 2). The Platte River caddisfly is in the family
Limnephilidae, or the northern caddisflies, subfamily Dicosmoceniae,
and genus Ironoquia (Wiggins 1977, p. 181; Alexander and Whiles 2000,
p. 1).
The caddisfly family Limnephilidae is considered to be the most
ecologically diverse family of Trichoptera (Holzenthal et al. 2007, p.
674) and is the largest caddisfly family in North America, with over
900 species in more than 100 genera (Holzenthal et al. 2007, p. 674).
The Limnephilidae family is dominant at higher latitudes and
elevations, has the widest distribution of any caddisfly family, and
comprises one-third of all Nearctic (ecozone comprising Arctic and
temperate areas of North America and Greenland) caddisfly species
(Wiggins 1977, p. 179). Caddisflies in this family may be collected
from springs, pools, seeps, marshes, bogs, fens, streams, rivers, and
lakes (Wiggins 1977, p. 179). Limnephilids largely feed on larger bits
of plant material, such as fallen leaves, or organic materials that
form atop rock surfaces (Wiggins 1977, p. 179).
The Ironoquia genus belongs to the subfamily Dicosmoceniae, which
mostly occurs in cool, lotic (running water) environments, except for
Ironoquia, which occurs in temporary pools (Flint
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1958, p. 59; Wiggins 1977, p. 248). The genus Ironoquia is comprised of
six species: the Platte River caddisfly (I. plattensis), I.
punctatissima (no common name) (Walker 1852), I. parvula (no common
name) (Flint 1958), I. dubia (no common name) (Stephens 1837), I.
lyrata (no common name) (Ross 1938), and I. kaskaskia (no common name)
(Ross 1944), with the Platte River caddisfly being the most recently
described (Encyclopedia of Life 2011, entire). All of these species
except I. dubia (Europe) occur only in North America (Williams and
Williams 1975, p. 829; [Cacute]uk and Vu[ccaron]kovi[cacute] 2010, pp.
232, 234).
Ironoquia is the only genus within the Dicosmoceniae subfamily that
occurs in temporary waters (Wiggins 1977, p. 248). In North America,
Ironoquia is mostly found throughout the central and eastern portions
of the United States (Wiggins 1977, p. 248) and is most often collected
from temporary pools or wetlands but can also occur in perennial waters
(Flint 1958, p. 61; [Cacute]uk and Vu[ccaron]kovi[cacute] 2010, p.
234). The Platte River caddisfly has been found to co-occur with I.
punctatissima, which is a common species on the Great Plains, but I.
punctatissima is morphologically distinct and much larger than the
Platte River caddisfly (Alexander and Whiles 2000, p. 1; Geluso et al.
2011, p. 1024).
The Platte River caddisfly is thought to be most closely related to
I. parvula (Alexander and Whiles 2000, p. 1), which occurs in Ohio and
the northeastern United States (Flint 1958, p. 59; Wiggins 1977, p.
248; Swegman et al. 1981, p. 141; Garono and MacLean 1988, p. 148).
Platte River caddisfly adults are smaller and have lighter color and
more pronounced spotting on the wings than I. parvula (Alexander and
Whiles 2000, p. 2). We find that Alexander and Whiles (2000, entire)
provide the best available information on the taxonomy of the Platte
River caddisfly, and no other challenges to the taxonomy have been
raised since the Platte River caddisfly was described. Therefore, we
consider the Platte River caddisfly a valid species for listing under
the Act.
Habitat Description
The Platte River caddisfly was discovered in 1997, in a warm-water
slough (backwater area or marsh that is groundwater fed) in south-
central Nebraska along the Platte River on Mormon Island (hereafter
type locality), which is land owned by the Platte River Whooping Crane
Maintenance Trust (hereafter Crane Trust (a conservation organization))
southwest of Grand Island, Nebraska (Whiles et al. 1999, p. 534;
Goldowitz 2012, pers. comm.). This slough had an intermittent
hydroperiod (duration of inundation) and held water 75-90 percent of
the time or about 275-330 days out of the year (Whiles et al. 1999, p.
534; Goldowitz 2004, pp. 2-3). The area lacked trees (Whiles et al.
1999, p. 534) and was located within the largest remaining tract of
native prairie in the Central Platte Valley (Goldowitz 2004, p. 2).
Intermittent wetlands, such as the type locality, have been
described as any water body that holds water for about 8 to 10 months
during the year (Wiggins et al. 1980, p. 100); some intermittent sites
may or may not completely dry in a year (Tarr and Babbitt 2007, p. 6).
These wetlands differ from ephemeral wetlands (that hold water for a
relatively short period of time (e.g., 4 months)) and permanent
wetlands (rarely dry) (Tarr and Babbit 2007, p. 6). Intermittent
wetlands dry when the groundwater table drops below the ground surface.
Since the Platte River caddisfly was discovered, surveys have
mostly found the caddisfly in sloughs with intermittent hydroperiods;
however, the caddisfly has also been found in sloughs with permanent
hydroperiods (Goldowitz 2004, p. 5; Meyer and Whiles 2008, p. 632;
Vivian 2010, p. 54; Geluso et al. 2011, p. 1024). In sloughs with
permanent hydroperiods, the caddisfly has been observed in lower
numbers, which is true of other Ironoquia species, likely because of
the presence of more predators in permanent waters (Wiggins et al.
1980, p. 148; Vivian 2010, p. 54). The caddisfly has not been observed
in ephemeral wetlands (Vivian 2009, pers. obs.).
In general, the intermittent wetlands where the caddisfly occurs
are found along the floodplains of the Platte, Loup, and Elkhorn Rivers
in central Nebraska (LaGrange 2004, p. 15) and are shallow, linear
depressions that are historical channel remnants of these river systems
(Friesen et al. 2000, p. 4-8). The presence of water in these sloughs
is influenced by groundwater levels and trapped surface run-in (Friesen
et al. 2000, p. 4-8). Groundwater levels are controlled by river stage
(flows), precipitation, and evapotranspiration (Wesche et al. 1994, p,
iii). Platte River flows are principally tied to snowmelt from the
Rocky Mountains and local precipitation events (Simons and Associates
2000, pp. 2-5), while Loup River and Elkhorn River flows are tied to
the Ogallala Aquifer (Peterson et al. 2008, p. 5). Sloughs that support
the caddisfly vary in their distance to the main river channel. Most
sloughs are adjacent to the main channel, while some occur in areas
more than 0.4 kilometers (km) (0.25 miles (mi)) away.
Sloughs with the Platte River caddisfly are typically described as
lentic (with little to no flow) (Whiles et al. 1999, p. 533; Alexander
and Whiles 2000, p. 2). However, two sites do contain some flow, and
the caddisfly appears to occur in higher densities in areas with
flowing water than in stagnant areas (Harner 2012, pers. comm.).
Because of their groundwater connection, sloughs with the caddisfly may
maintain thick ice cover on surface waters through the winter without
completely freezing to the bottom (Whiles et al. 1999, p. 534;
Goldowitz 2004, p. 2). Slough substrata often consist of a thick layer
of detritus and silt overlying sand (Whiles et al. 1999, p. 534;
Alexander and Whiles 2000, p. 6). Soils in the sloughs consist of a
mixture of loam, sand, and gravelly sand and tend to be frequently
flooded and poorly drained (Natural Resources Conservation Service
(NRCS) Web Soil Survey 2009, entire).
Because it is an inhabitant of intermittent waters, the Platte
River caddisfly is tolerant of large fluctuations in water chemistry
(Williams 1996, p. 634; Whiles et al. 1999, p. 534). Large variations
in water quality (e.g., pH, conductivity, total dissolved solids,
dissolved oxygen, turbidity, and temperature) have been observed among
five forested sites where the caddisfly occurs (Vivian 2010, pp. 81,
96). Furthermore, average conductivity and pH in sloughs with the
caddisfly reported by Vivian (2010, pp. 81, 96) differed from the
average values reported by Whiles et al. (1999, p. 534) and Geluso et
al. (2011, p. 1022). The gradient of water chemistry observed between
forested sloughs and the type locality is likely a result of the
differences in habitat types, and demonstrates that the Platte River
caddisfly can withstand a broad range of water quality.
Vegetation in sloughs occupied by the caddisfly is typical wetland
flora, such as Typha spp. (cattails), Schoenoplectus fluviatilis (river
bulrush), Eleocharis spp. and Cyperus spp. (sedges), and Lemna spp.
(duckweed); some sloughs support nonnative, invasive vegetation,
including Phalaris arundinacea (reed canarygrass), Phragmites (common
reed), and Lythrum salicaria (purple loosestrife). Plant species along
slough banks and margins include woody species, such as Fraxinus
pennsylvanica (green ash) and Populus deltoides (cottonwood), and grass
species, such as Spartina pectinata (prairie cordgrass)
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and smooth brome (Bromus inermis, invasive). Various forbs are also
present throughout the slough. Most areas where the Platte River
caddisfly has been observed since it was described have an abundance of
woody vegetation, which contrasts with the treeless, wet meadow
environment encountered at the type locality and one other population
at the Crane Trust (Whiles et al. 1999, p. 534; Vivian 2010, p. 56;
Vivian 2011, pp. 33-35). Overall, the Platte River caddisfly is
tolerant of a range of conditions, including variations in hydroperiod,
water quality, and vegetation, but thrives in intermittent sloughs.
Life History and Ecology
The Platte River caddisfly lifecycle was characterized by Whiles et
al. (1999, entire). The caddisfly is univoltine (one generation per
year). The adult flight period for the Platte River caddisfly is
between late September and mid-October. Adults first emerge around
late-September and live for about 7 to 10 days, with the entire
emergence period lasting 3 to 4 weeks. While active, adults oviposit
(lay eggs) on the surface film of the water, the eggs sink to the
bottom of the slough, and larvae hatch as first instars (life stage
between molts) sometime in November. Aquatic larvae overwinter in the
slough as first instars. In late winter, larvae construct their case
(Vivian 2010, pers. obs.) and begin feeding and growing rapidly and
proceed through four more instars. Between late April and early June,
fifth (final) instars climb upslope from the water and aestivate (pass
stressful time periods in a dormant condition) during the summer months
when it is typically dry along the adjacent slough banks (Whiles et al.
1999, pp. 535-536; Geluso et al. 2011, p. 1023). Platte River caddisfly
larvae eventually pupate (metamorphose between larva and adult) along
slough margins in the larval case. Pupation lasts about 4 weeks until
adult emergence in late September.
While in its aquatic stage, the Platte River caddisfly is
considered a shredder and largely feeds upon senescent (aged) plant
tissue (Whiles et al. 1999, pp. 542-543). As one of the few shredders
present in sloughs, the Platte River caddisfly plays an important role
in the decomposition of organic matter in these systems (Whiles et al.
1999, pp. 539, 543). In its terrestrial stage, the Platte River
caddisfly does not feed (Whiles et al. 1999, p. 537), and as an adult,
the species has the ability to ingest liquids (Holzenthal et al. 2007,
p. 648).
The Platte River caddisfly likely has a lifecycle adapted to the
intermittent wetlands found along the Platte, Loup, and Elkhorn River
systems (Whiles et al. 1999, p. 537; Vivian 2010, pers. obs.). For
example, larval emigration to adjacent mesic grassland habitat and
adult emergence were found to coincide with early summer drying and
fall inundation of the wetlands, respectively (Whiles et al. 1999, pp.
537, 542). The Platte River caddisfly is dependent upon water for the
egg and larval stages of its lifecycle, (e.g., for at least 7 to 8
months out of the year) (Whiles et al. 1999, pp. 537-539).
While most caddisflies have an entirely aquatic larval phase, all
Ironoquia species are known to aestivate in leaf litter near the
receding water line during the summer months prior to pupating (Flint
1958, p. 61; Williams and Williams 1975, p. 830; Wiggins 1977, p. 248;
Johansson and Nilsson 1994, p. 21; Whiles et al. 1999, p. 534).
However, some aestivating Platte River caddisfly larvae have been found
to burrow beneath the ground surface (Geluso et al. 2011, p. 1024).
This behavior may be a way to withstand summer drying of sloughs or to
avoid desiccation, as reported for other caddisflies (Mackay and
Wiggins 1979, p. 187; Wiggins et al. 1980, p. 179; Johannson and
Nilsson 1994, p. 21; Geluso et al. 2011, p. 1024), as soil temperatures
in unshaded areas can reach 54 degrees Celsius ([deg]C) (129 degrees
Fahrenheit ([deg]F)) in the summer (Vivian 2010, pers. obs.). This
behavior could protect aestivating larvae against late spring (May-
June) flows, which are characteristic of the Platte River system and
could scour (wash) larvae downstream (Simon and Associates 2000, p. 8)
and other disturbances characteristic of the Great Plains ecosystem,
such as livestock grazing (Geluso et al. 2011, p. 1024).
Historical Range and Distribution
Data collection on the range of the Platte River caddisfly began in
1999, shortly after it was discovered, and continued in 2004 (Goldowitz
2004, p. 3). Surveys were conducted at 48 locations along the Platte
and Loup Rivers, and the Platte River caddisfly was found at 9 of these
sites (Goldowitz 2004, p. 5). These populations occupied an
approximately 100-km (60-mi) stretch of the central Platte River that
extends from south of Gibbon, Nebraska (Kearney County), to Central
City, Nebraska (Merrick County). Surveys for the caddisfly on the Loup
River were negative (Goldowitz 2004, p. 9). Monitoring efforts in 2004
did not find the caddisfly at the type locality, despite a consistent
adult emergence pattern in the preceding 7 years and the species' prior
abundance at that site (Goldowitz 2004, p. 8). Because of its apparent
rarity, the caddisfly was designated a Tier 1 species in Nebraska as
per the State's natural legacy plan (Schneider et al. 2005, p. 93).
Tier 1 species are those that are at risk of extinction on a global
scale or at risk of becoming extirpated from Nebraska (Schneider et al.
2005, p. 17).
Current Range and Distribution
Through 2004, the Platte River caddisfly was only known from the
Platte River (Goldowitz 2004, p. 9). However, surveys for new Platte
River caddisfly populations resulted in the discovery of the species on
the Loup and Elkhorn Rivers in Nebraska in 2009 and 2010 (Vivian 2010,
p. 50). Close visual examination of adults and larvae at sites on the
Loup and Elkhorn Rivers demonstrated that the species was not I.
parvula and confirmed the presence of the Platte River caddisfly on
these systems. However, because of the distance between some caddisfly
populations on the Platte, Loup, and Elkhorn Rivers, we determined
there was a need to identify potential genetic differences for the
species among sites. Genetic analyses indicated that there is a low
amount of gene flow among all three rivers, and that a population
tested on the Elkhorn River was genetically divergent, but not
different, from the populations on the Platte and Loup Rivers
(Cavallaro et al. 2011, p. 7). This genetic divergence appears to be a
product of geographic isolation as opposed to habitat fragmentation.
The Platte River is formed at the confluence of the North Platte
and South Platte Rivers in west-central Nebraska, just east of North
Platte, and generally flows east until it meets the Missouri River
along the eastern edge of Nebraska (Williams 1978, pp. 1-2). The North
Platte River originates in the Rocky Mountains of Colorado, flows north
through central Wyoming and then southeast into Nebraska (Williams
1978, p. 1); the South Platte River originates in Colorado and flows
northeast until it meets the Platte River at North Platte, Nebraska
(Simons and Associates 2000, p. 2). Platte River flows are largely
dependent upon snowmelt from the Rocky Mountains and local
precipitation events (Simons and Associates 2000, pp. 2-5).
The Loup and Elkhorn Rivers are tributaries of the Platte River
system. The Loup River contains several tributaries, including the
North Loup, Middle Loup, South Loup, and Cedar Rivers in Nebraska. The
Loup River is
[[Page 52654]]
formed at the confluence of the Middle Loup and North Loup Rivers near
St. Paul, Nebraska, and flows east until it meets the Platte River at
Columbus, Nebraska, in the eastern third of the State. The Loup River
drains groundwater from the Sandhills and the underlying Ogallala
Aquifer, and its tributaries flow northwest to southeast, while the
Loup flows east or northeast until it meets the Platte River (Peterson
et al. 2008, pp. 2-5). The Elkhorn River drains wet meadows and plains
in north-central Nebraska, and flows east-southeast until it meets the
Platte River near Omaha, Nebraska (Peterson et al. 2008, pp. 2-5).
In Nebraska, there is a gradient of precipitation from west to
east. Just east of the Rocky Mountains in central Nebraska there is a
predominant rain shadow effect that results in low amounts of
precipitation in western Nebraska. Precipitation generally increases as
one travels east towards Nebraska's eastern border (Simon and
Associates 2000, p. 2).
Surveys for the Platte River caddisfly between 2009 and 2011
identified 35 caddisfly populations out of 115 sites visited, including
5 of the 9 sites identified by Goldowitz (2004, entire) (Vivian 2010,
p. 46; Geluso et al. 2011, entire; Figure 1 below). With these recent
survey efforts, the caddisfly is now known from a 390-km (240-mi)
stretch of the Platte River that runs from near Sutherland, Nebraska
(Lincoln County), to near Schuyler, Nebraska (Platte County), and from
the Loup and Elkhorn River systems (Figure 1 below). Within this range,
there is approximately a 155-km (93-mi) gap in the distribution of the
caddisfly between Hershey, Nebraska, and Elm Creek, Nebraska (Vivian
2010, p. 51). Twenty-four surveys for the caddisfly were conducted in
this gap, and the caddisfly was not found (Vivian 2010, p. 50).
[GRAPHIC] [TIFF OMITTED] TP30AU12.062
From recent survey efforts, one site near Shelton, Nebraska, is
presumed extirpated (Riens and Hoback 2008, p. 1; Vivian 2010, p. 48).
Also, the Platte River caddisfly was observed at the type locality in
2010 (Geluso et al. 2011, p. 1023), after not having been observed
there during surveys in 2004 and 2007-2009 (Goldowitz 2004, p. 8; Riens
and Hoback 2008, p. 1; Vivian 2010, p. 53). Survey work in 2009-2011
also identified 13 sites along the Platte, Loup, Elkhorn, and Cedar
Rivers that contained discarded larval cases but no live individuals
(Vivian 2010, p. 46). Finding a site with a caddisfly case in a slough
along the Cedar River indicates that the Platte River caddisfly is
likely present in the basin. However, observing live individuals at a
site is needed to confirm its presence there, because it is thought
that discarded larval cases degrade slowly and could represent
generations from previous years (Vivian 2010, pp. 49, 55-56).
Aside from the Cedar River, it appears that more surveys for the
Platte River caddisfly could result in the discovery of additional
populations on other river drainages in Nebraska, including the
Niobrara and Republican Rivers. More survey work on the Platte, Loup,
and Elkhorn drainages would likely result in the discovery of new
populations on these systems as well. Between 2009
[[Page 52655]]
and 2011, satellite imagery was used to identify potential caddisfly
habitat throughout Nebraska prior to conducting surveys (Vivian 2010,
p. 38). There are additional areas of remaining potential Platte River
caddisfly habitat along Nebraska's major river systems that have yet to
be surveyed (Vivian 2011, pers. obs.). Thus, ongoing surveys are likely
to expand the known range of the Platte River caddisfly.
Population Densities
At the type locality, the Platte River caddisfly was considered an
abundant component of the slough ecosystem. In 1997-1998, an average of
805 194 larvae per square meter (m\2\) was observed
throughout the aquatic life stage of the caddisfly lifecycle, and
410.67 larvae per m\2\ were present in the aquatic environment in May
1998 (Whiles et al. 1999, pp. 537, 540). Geluso et al. (2011, p. 1022)
reported a mean density of 553 284 Platte River caddisfly
larvae per m\2\ (n = 19) from a site at the Crane Trust on Shoemaker
Island (hereafter ``Wild Rose Slough''), which is located about 5 km
(3.2 mi) upstream of the type locality. With the exception of these two
sites, the Platte River caddisfly has been found to occur in lower
densities (Whiles et al. 1999, pp. 539-540).
In May of 2009 and 2010, aquatic larval densities were measured at
18 sites with a Platte River caddisfly population on the Platte River
only, and larval densities ranged from zero to 125.7 individuals per
m\2\ (Vivian 2010, p. 64). Aestivating (terrestrial life stage) larval
densities at 12 of 13 sites sampled ranged from zero to 116 individuals
per m\2\ (Vivian 2010, p. 65). Day and nighttime sampling found
anywhere between zero and eight adults per hour of observation (Vivian
2010, pp. 65-66).
The aquatic and terrestrial larval densities reported by Vivian
(2010, pp. 40-41) are not directly comparable to Whiles et al. (1999,
p. 535), because different methodologies were used, and a different
volume of sediment was sampled during the aquatic sampling period
(Meyer et al. 2011, p. 110). Meanwhile, Geluso et al. (2011, p. 1022)
used the same aquatic sampling method as Vivian (2010, pp. 40-41) but
sampled slightly earlier in 2010. Nonetheless, the methods used during
2009-2010 sampling were internally consistent, and these results
demonstrate that the caddisfly occurs in varying densities across its
range (Vivian 2010, pp. 40-41; Harner 2012, pers. comm.). Although some
densities reported by Vivian (2010) are low compared to what has been
reported for other caddisfly species (Mayer and Likens 1987, p. 266;
Roeding and Smock 1989, p. 152; Bunn and Hughes 1997, pp. 343-344;
Stewart and Downing 2008, p. 145), observations on the numbers and
density variations of Platte River caddisfly larvae and adults are
consistent with those reported for other Ironoquia species (Flint 1958,
p. 60; Swegman et al. 1981, p. 131; MacLean and MacLean 1984, p. 56;
Garono and MacLean 1988, p. 147; Gray and Johnson 1988, p. 180;
[Cacute]uk and Vu[ccaron]kovi[cacute] 2010, pp. 233-234). Therefore,
the Platte River caddisfly and Ironoquia spp., in general, are more
abundant in some areas than in others.
Although population densities have been reported for over half of
all known Platte River caddisfly populations, there is a lack of
general information on population trends for this species, with the
exception of a few sites, including the type locality, Wild Rose
Slough, one site near Shelton, Nebraska, and one site near Chapman,
Nebraska, where restoration work conducted by the Service in 2007
resulted in a population decline at that site. Sites with lower
population densities may always remain naturally low. Therefore, with
the information available and the increase in the number of known
populations, it is difficult to discern if the number of Platte River
caddisfly individuals and populations is remaining steady, increasing,
or decreasing.
Summary of Information Pertaining to the Five Factors
Section 4 of the Act (16 U.S.C. section 1533) and implementing
regulations (50 CFR part 424) set forth procedures for adding species
to, removing species from, or reclassifying species on the Federal
Lists of Endangered and Threatened Wildlife and Plants. Under section
4(a)(1) of the Act, a species may be determined to be an endangered or
threatened species based on any of the following five factors:
(A) The present or threatened destruction, modification, or
curtailment of its habitat or range;
(B) Overutilization for commercial, recreational, scientific, or
educational purposes;
(C) Disease or predation;
(D) The inadequacy of existing regulatory mechanisms; or
(E) Other natural or manmade factors affecting its continued
existence.
In making this finding, information pertaining to the Platte River
caddisfly in relation to the five factors provided in section 4(a)(1)
of the Act is discussed below. In considering what factors might
constitute threats to a species, we must look beyond the exposure of
the species to a particular factor to evaluate whether the species may
respond to that factor in a way that causes actual impacts to the
species. If there is exposure to a factor and the species responds
negatively, the factor may be a threat and, during the status review,
we attempt to determine how significant a threat it is. The threat is
significant if it drives, or contributes to, the risk of extinction of
the species such that the species warrants listing as endangered or
threatened as those terms are defined in the Act. However, the
identification of factors that could impact a species negatively may
not be sufficient to compel a finding that the species warrants
listing. The information must include evidence sufficient to suggest
that these factors are operative threats that act on the species to the
point that the species may meet the definition of an endangered or
threatened species under the Act.
Factor A. The Present or Threatened Destruction, Modification, or
Curtailment of the Species' Habitat or Range
Landscape-Level Changes in Hydrology
Reductions in groundwater levels or river flows as a result of
water development can adversely impact aquatic habitats and their
associated macroinvertebrate communities. Existing and future water
development along the Platte, Loup, and Elkhorn Rivers could adversely
impact the Platte River caddisfly and its habitat. Adverse impacts
could occur through the loss of water during critical life stages or
changes in hydrology that result in intermittent wetlands becoming too
ephemeral to support the Platte River caddisfly. We examine this topic
in detail below.
Hydroperiod can be an important factor in determining the
composition of macroinvertebrate communities in wetlands. For instance,
Whiles and Goldowitz (2005, p. 466) found that slough hydroperiod
influenced macroinvertebrate taxa diversity and abundance, with more
taxa present in intermittent sloughs than in sloughs with more
ephemeral or permanent hydroperiods. Sloughs with intermittent
hydroperiods typically have fewer predators than permanent wetlands and
can offer safe refugia for various taxa if they can withstand habitat
drying (Williams 1996, p. 634; Wissinger et al. 1999, p. 2103; Tarr and
Babbitt 2007, p. 3). Sites with more permanent hydroperiods likely
offer a more suitable environment for potential predators of the
caddisfly, such as fish and amphibians, thereby reducing larval
densities (Whiles and Goldowitz 2001,
[[Page 52656]]
p. 1836; Whiles and Goldowitz 2005, pp. 468, 470). Certain permanent
sloughs with the Platte River caddisfly also appear to be more food-
limited than others as these areas have less standing vegetation
(Vivian 2011, p. 18). The amount of available food can limit the
abundance of shredder species (Roeding and Smock 1989, p. 149), such as
the Platte River caddisfly (Vivian 2011, p. 18).
The type locality from which the Platte River caddisfly was
described had an intermittent hydroperiod (Whiles et al. 1999, p. 536).
The Platte River caddisfly was not found at four other sloughs near the
type locality during the time of the life history study; these sloughs
had hydroperiods that differed from that of the type locality--they
were thought to be either too ephemeral or permanent for the caddisfly
(Whiles et al. 1999, p. 542; Whiles and Goldowitz 2001, p. 1832; Whiles
and Goldowitz 2005, p. 466). Also, the Wild Rose Slough site contains
ephemeral, intermittent, and permanent reaches, and the Platte River
caddisfly has only been observed in the intermittent (Vivian 2010,
pers. obs.) and permanent reaches of the slough (Geluso et al. 2011, p.
1022). In other parts of its range, the Platte River caddisfly has been
found in sloughs with more permanent hydroperiods, albeit in lower
numbers than in sloughs with intermittent hydroperiods (Vivian 2010, p.
54; Geluso et al. 2011, p. 1022).
The caddisfly occurs in higher densities in intermittent sloughs
than in sloughs with permanent hydroperiods. For instance, the type
locality and Wild Rose Slough have intermittent hydroperiods (Vivian
2010, pers. obs.) and have supported or currently support the largest
known larval densities of the Platte River caddisfly (Whiles et al.
1999, p. 536; Vivian 2010, pers. obs.; Geluso et al. 2011, p. 1022).
Relatively low densities of the caddisfly have been found at other
sites that have longer hydroperiods and experience less water level
fluctuation (Vivian 2010, p. 54). Thus, it is thought that sloughs with
intermittent hydroperiods are ideal for the Platte River caddisfly.
Although intermittent wetlands represent ideal Platte River caddisfly
habitat, permanent wetlands may become important during and following a
drought as sites that support source populations for recolonization
following extended dry periods. However, ephemeral wetlands do not
remain wet long enough to support the species' lifecycle.
Overall, landscape-level changes in hydrology that result from
reservoir construction, river channel diversions, and groundwater
withdrawal for irrigation could adversely impact the Platte River
caddisfly and its habitat through the loss of water during critical
life stages or degradation of its habitat. Since European settlement in
the 1850s, the Platte, Loup, and Elkhorn Rivers have all experienced
some degree of water development for various purposes; the Platte River
has experienced the largest amount of modification of these systems.
Starting in the mid-1800s, the tributaries of the Platte River were
gradually developed to deliver water for irrigation via main and
lateral canals, and eventually larger water storage projects along the
main channels of the river were constructed (Eschner et al. 1981, pp.
3, 5). Water development projects were implemented to make the region
more suitable for agriculture, and more than 7,000 canals were
constructed along the river between 1851 and 1930 (Simons and
Associates 2000, pp. 5-9). Over-appropriation of water in the Platte
Basin became an issue as early as 1876, and dams were constructed to
create more reliable supplies of water (Eschner et al. 1981, p. 10;
Simons and Associates 2000, pp. 7-8).
Several hundred storage reservoirs and six principal dams are
present in the Platte River Basin, and together they impound more than
7.6 million acre-feet of water for irrigation (Simons and Associates
2000, p. 8). Each reservoir project contains several miles of
associated canals (Simons and Associates 2000, p. 13). Because of dams
and diversions along the Platte Basin, over 70 percent of the Platte
River flow is estimated to be diverted before it reaches Lexington,
Nebraska (Currier et al. 1985, p. 120; Sidle et al. 1989, p. 91), which
is about 48 km (30 mi) upstream of where most Platte River caddisfly
populations along the Platte River are found. As a result of this
development, the river has been described as one of the most heavily
managed river systems in the United States (Simons and Associates 2000,
p. 14; LaGrange 2004, 274 15).
The Loup River has also been impacted by water development
projects. The Loup Basin includes the North, Middle, and South Loup
Rivers, and within the basin there are four mainstem diversion dams
(U.S. Bureau of Reclamation (USBR) 2011, entire). The largest diversion
dam, the Loup Diversion Dam, diverts around 69 percent of the Loup
River flow away from the main channel for a distance of 35 miles in
Nance and Platte Counties in Nebraska (Loup Power District and HDR
Engineering 2008, p. 4-39). Each diversion dam has several miles of
associated lateral canals to divert water to irrigated farmland (USBR
2011, entire). Also, three impoundments are present along tributaries
of the Loup River Basin (Loup Power District and HDR Engineering 2008,
pp. 3-5), but the system lacks mainstem dams. The Elkhorn River is
generally free of impoundments and diversions (LaGrange 2004, p. 21;
Peterson et al. 2008, p. 5).
Habitat Loss Resulting From Changes in Hydrology
Dams and diversion projects are known to result in changes in
hydrological, geophysical, and ecological characteristics of river
systems (Simons and Associates 2000, p. 15; Schramm et al. 2008, pp.
237-238). Dams and diversions dampen the natural flow regime and change
the hydrology of river systems, contribute to the downcutting and
degradation of the river bed, reduce the amount of sediment flowing
downstream, and reduce the amount of water reaching floodplain wetlands
(Kingsford 2000, p. 109; Bowen et al. 2003, p. 809). These changes
affect the ability of managed river systems to remain in a state of
dynamic equilibrium, which contributes to the creation and maintenance
of a diversity of habitats along a river's floodplain (Bowen et al.
2003, p. 809). Water development projects may ultimately cause a river
to become disconnected from its floodplain (Bowen et al. 2003, p. 809)
and reduce the ability of rivers to continually inundate and create new
backwater habitats via peak flows (Schramm et al. 2008, pp. 237-238).
Channel Narrowing
As a result of reduced flow through the Platte River system, the
main channel of the Platte River narrowed by about 65 to 80 percent
between the mid-19th century and 1969 (Williams 1978, p. 8; Eschner et
al. 1981, p. 45) and further narrowed by up to 25 percent between 1970
and 1999 (Murphy et al. 2004, p. 102). Channel narrowing has resulted
in a reduction in wetland habitat along the Platte River through a
drying of adjacent sloughs. Between 1938 and 1982, an estimated 45.2
percent of wet meadow habitat along the central Platte River was lost
(Sidle et al. 1989, pp. 98-99), and this corresponded to a 53.4 percent
reduction in active channel width during the same time period (Peake et
al. 1985, entire; Sidle et al. 1989, pp. 98-99). The drying of linear
slough depressions along the river also facilitated the development of
row crops along what used to be wet bottomlands (Currier et al. 1985,
p. 113).
[[Page 52657]]
Many wetlands were initially converted to cropland through wetland
draining via ditches and land leveling (Currier et al. 1985, p. 113).
Wetland losses and channel shrinkage data for the Loup River are
currently unavailable; however, wetland losses have likely occurred
concurrent with the narrowing of the river channel downstream of
diversion projects.
Historically, channel narrowing on the Platte and Loup River
systems resulting from water development likely resulted in direct
losses of suitable Platte River caddisfly habitat prior to the species'
discovery in the late-1990s. During recent survey efforts, the Platte
River caddisfly was not found between Hershey and Elm Creek, Nebraska,
despite 24 surveys being conducted in this reach (Vivian 2010, p. 50).
We do not know if the caddisfly ever occurred in this stretch of river,
but it is present upstream and downstream of Hershey and Elm Creek,
Nebraska, respectively (Vivian 2010, p. 50), and this stretch is likely
one of the most dewatered and incised (disconnect of a river from its
floodplain as a result of a decline in river bed elevation) portions of
the Platte River (Murphy et al. 2004, p. 56). Since the species was
first described in 2000, no known population losses have occurred as a
result of channel narrowing and subsequent wetland drying.
Aside from the draining of adjacent wetlands, channel narrowing has
resulted in an increase in woody vegetation cover along the Platte
River (Johnson 1994, entire). Downstream of Kearney, Nebraska, channel
narrowing continues to reduce the amount of active channel area, and
the amount of forest cover continues to increase (Murphy et al. 2004,
p. 95), despite no new impoundments having been constructed in the
Platte basin since 1956 (Johnson 1994, pp. 77-78). The establishment
and proliferation of woody vegetation along the river acts to stabilize
the river and can further contribute to channel narrowing through the
trapping of sediments (Friedman et al. 1996, p. 341). Meanwhile, an
increase in forest cover is not thought to have an adverse impact on
the Platte River caddisfly, because most known caddisfly populations
are found in forested wetlands, and some forested sloughs support
relatively high larval densities of the Platte River caddisfly (Vivian
2010, p. 64). It is unlikely that any future increases in forest cover
will adversely affect the Platte River caddisfly.
Channel Degradation
Aside from channel narrowing, impoundments and diversions can
contribute to the downstream degradation of river systems, and these
projects can have lasting impacts. Impacts to the Platte River
resulting from past water development projects, which may affect the
caddisfly, are ongoing. For instance, reduced sediment loads resulting
from impoundments that block the passage of sediments and water
discharges below diversion returns and dams are known to impact river
systems and result in channel bed degradation. The North Platte River
historically provided the majority of the sandy sediment to the Platte
River system, but the amount of sediment inputs to the river greatly
declined with the closing of the mainstem dams on the North Platte
River (Murphy et al. 2004, p. 101). Near Overton, Nebraska, the
Johnson-2 (J-2) diversion return releases sediment-free water into the
Platte River and creates localized scour and an additional sediment
imbalance.
As a result of impoundments and diversion returns, less sediment
flows into the Platte River than flows out, and this contributes to the
erosion and a lowering of elevation of the river bed (Murphy et al.
2004, p. 101). Erosion may also result from a coarsening of sediments
in the river, which is a result of coarser sediment being supplied from
the South Platte River as opposed to the fine sands that used to come
from the North Platte River (Murphy et al. 2004, p. 115). Erosion
results from a change in sediment size, because smaller sediment is
transported downstream more quickly than coarser sediments (Murphy et
al. 2004, p. 119). This downcutting (or incision) further narrows the
active channel and acts to drain adjacent floodplain wetlands (Murphy
et al. 2004, p. 129). Channel incision resulting from the sediment
imbalance along the Platte River is thought to be largely complete
upstream of Kearney, Nebraska, but has only slightly affected the river
between Kearney and Grand Island, Nebraska, indicating that the trend
of degradation is moving downstream (Murphy et al. 2004, pp. 113, 129).
Channel incision and degradation resulting from the sediment imbalance
in the Platte River and a coarsening of sediments is anticipated to
take decades to be fully complete (Murphy et al. 2004, pp. 128-130).
The effects of channel degradation and its impacts on the Platte
River caddisfly and its habitat can be observed downstream of the J-2
return. Diversion returns, like the J-2 return, that put clear water
directly into the main channel of the Platte River, can contribute to
the downcutting of the river bed and subsequent draining of adjacent
floodplain wetlands. For instance, in 2010, surveys for the Platte
River caddisfly were conducted downstream of the J-2 return near
Overton, Nebraska, at Dogwood Wildlife Management Area (WMA). Within
the WMA, several linear depressions were observed, and these areas were
dry but showed signs of past beaver (Castor canadensis) activity,
indicating that the area had once supported slough habitat (Vivian
2010, p. 51). Given that the depressions were dry, habitat for the
caddisfly was absent (and so was the species) and, therefore, it seems
that the downcutting of the Platte River near Overton, Nebraska, has
contributed to the loss of potentially suitable caddisfly habitat at
Dogwood WMA.
The effects of the J-2 return can be observed up to 29 km (18 mi)
downstream of the return, although these effects are most pronounced
closest to the return (Murphy et al. 2004, p. 142). Between 1989 and
2002, the Platte River bed depth eroded 1.8 meters (6 feet) immediately
downstream of the J-2 return, and eroded 0.76-meter (2.5 feet) 29 km
(18 mi) downstream from the return during the same time period (Murphy
et al. 2004, p. 106). At Grand Island, Nebraska, the river bed eroded
0.27-meter (0.89-foot) between 1933 and 1995 (Murphy et al. 2004, p.
113). It is anticipated that the process of incision as a result of the
J-2 return will continue downstream all the way to Grand Island, but it
is expected to progress slowly (Murphy et al. 2004, pp. 113-114). For
instance, the river could incise by 0.60-meter (2 feet) from 1940 bed
elevation levels within 100 years, 48 km (30 mi) downstream of the
return. However, these same impacts are expected to take 400 years to
affect the area 100 km (60 mi) downstream of the return (Murphy et al.
2004, p. 114), an area where seven of the 35 known Platte River
caddisfly populations occur. This incision could further narrow the
central Platte River and contribute to the draining of adjacent
wetlands and sloughs occupied by the Platte River caddisfly.
It is likely that channel incision has contributed to a loss in
available Platte River caddisfly slough habitat in the past and could
adversely affect the remaining sloughs on the central Platte River
(Lexington, Nebraska to Chapman, Nebraska, where several populations of
the Platte River caddisfly occur) in the future. The impacts of channel
degradation on Platte River caddisfly habitat are best demonstrated by
the effects observed at Dogwood WMA and
[[Page 52658]]
at the Crane Trust on Shoemaker and Mormon Islands. Harner and Whited
(2011, pp. 17-18; Harner 2012, pers. comm.) demonstrated that although
there was two times more river discharge in the Platte River in 1999
than in 1951, less slough habitat was available at the Crane Trust in
1999 than was present in 1951. Between 1951 and 1999, the amount of
available slough habitat declined by 0.3-hectare (0.8-acre) at Wild
Rose Slough (which is deeper and more entrenched, resulting in less
surface area lost) on Shoemaker Island and 3.6 hectares (8.8 acres), or
about 28 percent, at the type locality on Mormon Island (Harner and
Whited 2011, pp. 17-18). Declines in the amount of slough habitat were
attributed to channel incision of the Platte River, or a drop in the
groundwater table, or both, as land leveling has not occurred along the
stretch of the river owned by the Crane Trust. These results
demonstrate that even though river discharge in 1999 was greater than
in 1951, more water in the Platte River does not necessarily mean that
the floodplain will be inundated enough by elevated groundwater to
support sloughs where the Platte River caddisfly occurs (Harner and
Whited 2011, p. 23).
Currently, the Crane Trust area supports the highest known
densities of the Platte River caddisfly (Whiles et al. 1999, p. 537;
Vivian 2010, p. 47; Geluso et al. 2011, p. 1022) and is one of the
largest remaining stretches of intact prairie in the Central Platte
Valley. However, although the Crane Trust protects the parcel where the
caddisfly occurs, this area is not buffered from the effects of
upstream water development and nearby groundwater pumping (Harner and
Whited 2011, pp. 23-24; Harner 2011, pers. comm.). The documented
decline in the amount of available slough habitat between 1951 and 1999
(Harner and Whited 2011, entire) illustrates that effects of past and
current degradation to the river channel are ongoing even though there
have been no major water projects implemented on the Platte River since
1956 (Johnson 1994, p. 78). If left unchecked (Murphy et al. 2004, p.
114), future channel degradation could eventually result in as much as
a total loss of Platte River caddisfly habitat at the Crane Trust and
other nearby sloughs. For instance, Harner and Whited (2011, p. 14)
demonstrated that groundwater declines greater than 0.5-meter (1.5-2.0
feet) from 1999 levels could result in slough drying at the type
locality in years with similar precipitation and river discharge
(Harner and Whited 2011, p. 20).
Although Harner and Whited (2011) demonstrated an ongoing trend in
channel degradation within the central Platte River near the Crane
Trust at Alda, Nebraska, the Platte River caddisfly is still present at
the type locality and Wild Rose Slough more than 10 years following
1999 (year of reference used in the study). There are also extant
Platte River caddisfly populations upstream of the Crane Trust, where
the effects of channel degradation are more pronounced, such as near
Elm Creek, Nebraska, where the channel bed incised by 0.76-meter (2.5
feet) between 1989 and 2002 (Murphy et al. 2004, p. 106). Meanwhile,
the type locality and Wild Rose Slough occur more off channel than the
forested sloughs adjacent to the river channel and may be less buffered
from the effects of channel incision, because hydroperiod is known to
decrease with increasing distance from the river channel (Whiles et al.
1999, p. 533). Therefore, habitat loss at the Crane Trust likely does
not represent the norm throughout the range of the Platte River
caddisfly.
If left unchecked, future channel degradation could result in
future losses in slough habitat and subsequent extirpation of the
Platte River caddisfly from the central Platte River. However, various
programs and entities are acting to maintain current habitat conditions
on the central Platte River. The central Platte River is actively
managed by several organizations to benefit endangered (E) and
threatened (T) species (whooping crane (Grus americana) (E), interior
least tern (Sterna antillarum athalassos) (E), piping plover
(Charadrius melodus) (T), and pallid sturgeon (Scaphirhynchus albus)
(E)) that depend on an open and braided river system. One such
organization is the Headwaters Corporation, which is the
nongovernmental organization responsible for overseeing the Platte
River Recovery Implementation Program (PRRIP) (discussed more below and
under Factor D).
PRRIP was established in 2006, by an agreement between the Bureau
of Reclamation, the Service, and the States of Colorado, Wyoming, and
Nebraska to manage Platte River flows and habitat to meet the needs of
endangered and threatened species that use the Platte River. For
instance, PRRIP plans to clear and lower vegetated islands in the river
to create a more open channel to benefit endangered species, and this
action would increase the amount of sediment in the river (Murphy et
al. 2004, p. 143; U.S. Department of the Interior (DOI) 2006, p. 5-60).
PRRIP also seeks to offset the sediment imbalance in the river by
adding sand to the central Platte River (DOI 2006, p. 5-55) and release
pulse flows to maintain present channel conditions (DOI 2006, p. 3-11).
Outside PRRIP, some work of removing riparian vegetation has already
been executed by organizations such as the Nebraska Public Power
District (Kinzel et al. 2006, entire). Other entities, such as the
Partners for Fish and Wildlife Program (PFW), are actively restoring
sloughs along the central Platte River to benefit wildlife, and these
areas could eventually provide suitable habitat for the Platte River
caddisfly. Ongoing efforts to maintain and improve current conditions
along the central Platte River should help stem the ongoing degradation
of the river and reduce the amount of potential losses of slough
habitat throughout the Platte River portion of the species' range.
As mentioned previously, water development on the Loup and Elkhorn
Rivers has not been as extensive as it has along the Platte River.
While there are diversions in place along the Loup River, these
diversions have not resulted in extensive channel incision and
degradation as has been observed along the Platte River. This can be
demonstrated by the lack of vegetation encroachment onto the active
river bed. Channel narrowing downstream of diversion projects on the
Loup River Basin has likely resulted in a loss of slough habitat in the
past. However, the Platte River caddisfly is present immediately
upstream of Kent Diversion Dam, and the species is present immediately
downstream of the Loup Diversion Dam. The populations in the vicinity
of these projects appear secure, because there appears to be ample
slough habitat to support the caddisfly at these sites (Vivian 2010,
pers. obs.). Potentially suitable habitat that has not been surveyed is
also present downstream of all four main diversion projects in the Loup
River Basin (Vivian 2012, pers. obs.). Meanwhile, no large-scale
projects on the Loup or Elkhorn Rivers are planned. Because of ongoing
efforts to maintain present channel conditions in the central Platte
River, which is the most degraded portion of the range of the Platte
River caddisfly, and because of a general lack of channel degradation
on the Loup and Elkhorn Rivers, we conclude that channel degradation
does not pose a threat to the Platte River caddisfly.
Altered Hydrograph
An altered hydrograph (graph of stream flow through time) can
result
[[Page 52659]]
from dams and diversion projects. For instance, dams impound water and
reduce the amount of water flowing through a river system. Diversion
projects can result in a changed hydrograph by altering the timing of
flows through a river system and can reduce the amount of water flowing
downstream. Historically, the Platte River received a late-spring rise
as a result of runoff from Rocky Mountain snowmelt, and water levels
then receded through the summer months, with the river nearly drying
completely in some years (Eschner et al. 1981, pp. 19-20; Simons and
Associates 2000, p. 8). Because of water development projects,
primarily dams, the historical hydrologic regime of the Platte River
has been altered. For instance, at North Platte, Nebraska, peak flows
declined from 20,000 cubic feet per second (cfs) in the late 1800s to
less than 5,000 cfs after 1940 (Simons and Associates 2000, p. 16).
Dams are also known to augment base flows in a river system, meaning
that some floodplain wetlands never go dry (Kingsford 2000, p. 111).
Following water development on the Platte River, periods of no or
little flow have decreased (Simons and Associates 2000, p. 44). A
reduction in natural periods of low flow could impact the intermittency
of sloughs where the Platte River caddisfly occurs by increasing the
permanency of water in certain areas. Despite the potential for sloughs
along the Platte and Loup Rivers to be more permanent, the Platte River
caddisfly has presumably existed with the presence of dams on the
landscape for over 100 years. The species also occurs in permanent
sloughs, and these areas could become important source populations for
other intermittent wetlands following extended dry periods or drought.
Wetlands that were historically intermittent may have become ephemeral
wetlands unsuitable for the caddisfly concurrent with water
development. However, we have no information to indicate that this has
occurred since the species was described in 2000.
At this time, there is no available information to indicate that an
altered hydrograph is adversely affecting any populations of the Platte
River caddisfly or has resulted in population losses throughout its
range. Therefore, we do not consider a changed hydrograph to pose a
threat to the Platte River caddisfly.
Invasive Species
Along the Platte River, changes in hydrology have contributed
significantly to the encroachment of woody and exotic vegetation onto
what used to be the active river bed (Currier et al. 1985, p. 119;
Johnson 1994, p. 47). In 2002, several areas of the Platte River went
completely dry for 2 months because of drought, and in 2003, low to
zero flows were recorded for extended periods of time within the Big
Bend reach of the Platte (80-mile stretch of the Platte River between
Overton and Chapman, Nebraska) (Service 2006, p. 113). During this
time, dense invasive vegetation grew within the Platte River channel as
a result of lower flows. Phragmites australis (common reed or
Phragmites) and Phalaris arundinacea (reed canarygrass), two non-
native, invasive species, have proliferated on previously barren
sandbars and in wetlands along the Platte River in the last decade.
Historically, encroaching vegetation would have been washed away by ice
scour, or high spring flows (now dampened by water development), or
both (Service 2006 p. 163), but active removal is now required to keep
invasive species in check. Invasive species have not proliferated on
the Loup and Elkhorn Rivers as much as on the Platte. Only P.
arundinacea has been observed in sloughs along the Loup River and in
lower abundances than in sloughs along the Platte River.
In the United States, there are introduced and native varieties of
Phragmites australis, and the introduced and hybridized forms have
become highly invasive in several States, including Nebraska (NRCS
2002, entire; Blossey 2003, entire). P. australis can be up to 15 feet
tall and quickly crowds out native wetland species once established
(Michigan Department of Environmental Quality 2011, entire). There are
also native and introduced ecotypes of Phalaris arundinacea, and the
species can be aggressive and invade wetlands. P. arundinacea has been
observed to form dense, monotypic stands and impenetrable mats of stems
and leaves and crowd out native plant species (Wisconsin Department of
Natural Resources 2007, entire). P. arundinacea was introduced from
Europe for agricultural use (Maurer et al. 2003, p. 16) and may be the
most pervasive emergent plant in wetlands in the Midwest (Spyreas et
al. 2010, p. 1254). Both P. australis and P. arundinacea have likely
spread along the Platte River as a result of deliberate introductions
and changes in hydrology (Andersen et al. 2004, p. 787; Strayer et al.
2006, p. 649).
Both Phragmites australis and Phalaris arundinacea have been
observed in sloughs where the Platte River caddisfly occurs; however,
P. arundinacea is more abundant and more often encountered in these
wetlands (Vivian 2010, pers. obs.). These invasive plant species have
been observed at 24 out of 35 sites with the caddisfly (Vivian 2011,
pers. obs.) and appear to have degraded habitat at five sites with the
caddisfly along the Platte River. At three sites, P. arundinacea
appears to have grown thick enough to completely dry out slough margins
and to have reduced the amount of available Platte River caddisfly
habitat at these sites (Vivian 2009, pers. obs.). P. australis is or
was the dominant vegetation present at two sloughs where the caddisfly
occurs when these areas were surveyed (Vivian 2009, pers. obs.); this
plant has potentially reduced the habitat quality at these sites, as
these sites support the lowest known densities of the Platte River
caddisfly (Vivian 2010, p. 64.). Nonetheless, no extirpations have been
observed as a result of displacement by invasive species, and work is
underway along the central Platte River to control and reduce the
spread of P. australis (The Nature Conservancy 2011, entire). In other
sloughs that support exotic vegetation, there is no evidence to suggest
that P. australis or P. arundinacea are encroaching to the point where
habitat quality is being reduced or will be reduced in the near future.
Because invasive species appear to be impacting the Platte River
caddisfly at only a small number of sites throughout its range, we do
not consider invasive plant species to pose a threat to the Platte
River caddisfly.
Groundwater Development
Following dam construction in the Platte Basin, irrigation demands
were met through the pumping of groundwater (Eschner et al. 1981, p.
10), particularly along the central Platte River (Currier et al. 1985,
p. 87). The central Platte River remains the most heavily irrigated
region in Nebraska, with an average of 2 to 16 registered groundwater
wells per mile (University of Nebraska at Lincoln, School of Natural
Resources (UNL-SNR) 2011a, entire). As of 2008, there were 1.3 million
acres of irrigated cropland within the Loup Basin (Loup Power District
and HDR Engineering 2008, p. 3-1). Throughout most of the Loup and
Elkhorn Basins, there are up to 4 registered irrigation wells per mile,
but there can be up to 16 wells per square mile in the Loup Basin (UNL-
SNR 2011a, entire).
Groundwater pumping can result in a lowering of the water table and
contribute to subsequent wetland drying and loss (van der Kamp and
Hayashi 1998, p. 51; LaGrange 2004, p. 13). It is possible that pumping
groundwater for
[[Page 52660]]
irrigation contributed to some Platte River caddisfly habitat loss
historically throughout the species' range, particularly in the central
Platte River (Big Bend reach) where irrigation dominates the valley
(Currier et al. 1985, p. 87). However, available data on monitored
groundwater levels do not indicate that this has occurred or is
occurring on a wide scale throughout the range of the Platte River
caddisfly.
Along the eastern portion of the central Platte River (east of
Buffalo County line), groundwater levels in some isolated areas near
the river declined 1.5 to 3.0 meters (5 to 10 feet) between pre-
development (1950 or later for some parts of Nebraska) (McGuire 2011,
pp. 1, 4) and spring 2011 (UNL-SNR 2011b, entire). The remainder of the
groundwater table near the Platte River experienced little to no change
or an increase (UNL-SNR 2011b, entire). Throughout the entire central
Platte region and near the river, the groundwater table declined 0.3 to
1.5 meters (1 to 5 feet) between spring 2001 (species described in
2000) and spring 2011 (UNL-SNR 2011c, entire) but increased 0.6 to 1.5
meters (2 to 5 feet) between spring 2006 and spring 2011 (UNL-SNR
2011d, entire). The groundwater level declines observed between 2001
and 2011 may be attributed to drought conditions in Nebraska during the
first half of the 2000s (see Climate Change, below).
Aside from a few small, isolated areas where groundwater levels
declined close to the Loup River, between 1950 and 2011, groundwater
levels increased by at least 1.5 meters (5 feet) throughout most of the
Loup and part of the Elkhorn Basins (UNL-SNR 2011b, entire). Elsewhere
in the Elkhorn Basin, there was no change in observed groundwater
levels between 1950 and 2011 (UNL-SNR 2011b, entire). It is unlikely
that observed increases in the groundwater table along the Loup and
Elkhorn Rivers have contributed to losses in the amount of slough
habitat available to the caddisfly.
Where groundwater levels have dropped within the range of the
Platte River caddisfly, it is possible that a loss in slough habitat
has occurred through the loss of inundated wetland acres. However,
since the species was described, drops in the groundwater table due to
pumping are not known to have resulted in extirpations of any caddisfly
populations. Also, the amount of loss in slough habitat is likely
limited, because the groundwater table dropped in only three isolated
areas within the range of the caddisfly between 1950 and 2011 (UNL-SNR
2011b, entire). Only one of these areas overlaps with extant Platte
River caddisfly populations, and this area is along the central Platte
River. The other two areas near where groundwater levels have declined
since pre-development support slough habitat that has not yet been
surveyed for the caddisfly.
There is the potential for ongoing and future groundwater
withdrawals to adversely impact the Platte River caddisfly and its
habitat in the future, particularly given the recent increase in demand
for grain. For instance, in the Lower Loup Natural Resources District
(LLNRD), which encompasses the Loup River and its tributaries upstream
of Columbus, Nebraska, to the west end of Loup and Custer Counties,
10,000 additional acres were approved to be added to the amount of
irrigated acres between 2010 and 2013 (Lower Loup Natural Resources
District 2011, entire), and so the groundwater table in that region may
see declines with the increase in irrigation. Within the Central Platte
Natural Resources District (CPNRD), 2,500 new acres were opened for
development in 2012 downstream of Chapman, Nebraska. Future declines in
the amount of slough habitat on the Platte, Loup, and Elkhorn Rivers
associated with the increased demand for groundwater usage may occur.
Although the amount of slough habitat available to the caddisfly
has the potential to decline in the future concomitant with the
increase in grain production across at least some of the species'
range, existing regulations are likely to limit the extent to which
this can occur. Along most of the central Platte River, we have
determined that groundwater sources are relatively secure, because,
presently, there is a moratorium on new groundwater wells that pump
more than 50 gallons per minute, and no new well permits can be issued
unless the amount of consumptive water use is offset (retired elsewhere
in the basin) (CPNRD 2011, pp. 3-4). Therefore, current conditions are
not anticipated to worsen with respect to groundwater pumping in the
central Platte Basin, which is considered to be the most degraded
portion of the species' range. Also, because the sloughs along the
Platte River are closely tied to surface water flows within 0.8 km (0.5
mi) of the river (Hurr 1981, p. H7), efforts to increase shortages to
target flows in the Platte River under the PRRIP should maintain
current conditions in sloughs along the river. Elsewhere in the Loup
and Elkhorn Basins, groundwater and surface water resources are being
managed by Nebraska's natural resources districts, and by State law,
these areas cannot exceed the fully appropriated designation.
As part of Nebraska State law LB 962, passed by the State
legislature in 2004, groundwater well permits and surface water permits
are carefully managed so that river flows do not reach the over-
appropriated designation, because it has been recognized that surface
flows are tied to groundwater levels near the river and vice versa.
Nebraska State law requires that there be a balanced use of ground and
surface waters in Nebraska to ensure the long-term sustainability of
these supplies (Peterson et al. 2008, p. 2). Limited numbers of acres
are being allowed for well drilling on an annual basis in the Loup and
Elkhorn Basins. However, stays are placed on the construction of new
wells once a river basin is deemed fully appropriated (Ostdiek 2009, p.
2). A fully appropriated designation ((Neb. Rev. Stat. Sec. 46-713(3)
(Reissue 2004, as amended)) means that based on current groundwater and
surface water usage, average streamflows are insufficient to meet the
long-term demands within a basin (Peterson et al. 2008, p. 5).
Following any fully appropriated designation, the Nebraska Department
of Natural Resources (NDNR) and applicable natural resource district
must create an integrated management plan to achieve a sustainable
balance between water demands and supplies (Peterson et al. 2008, p.
5). If an area becomes over-appropriated, State law requires that the
applicable natural resource district work with its stakeholders on
returning the basin to a fully appropriated status (Ostdiek 2009, p.
2).
Since the Platte River caddisfly was described in 2000, no
information has become available to indicate that any net loss in
slough habitat has occurred as a result of groundwater pumping. At this
time, the Service does not have data showing that the quantity of water
has been lowered or that the current water withdrawals are impacting
the Platte River caddisfly habitat or will impact the Platte River
caddisfly in the near future. Declines in the groundwater table due to
drought resulted in two localized caddisfly extirpations; however, the
species is now found again at the type locality, and the groundwater
table has since rebounded in that area. If habitat loss has occurred,
we estimate that the amount has been negligible, because groundwater
declines between 1950 and 2011 have occurred only within a small
portion of the species' range. The Platte River caddisfly is extant in
the area of the Platte River where the largest documented drops in the
groundwater table have occurred. The species is also present in the
area
[[Page 52661]]
of the Platte River where there is the highest density of registered
irrigation wells (UNL-SNR 2011a, entire). Elsewhere, groundwater levels
have increased, possibly because of seeps that parallel the river
channel (Murphy et al. 2004, p. 47) and groundwater recharge from
lateral canals (Peterson et al. 2008, p. 13), and, therefore, habitat
losses cannot be attributed to a declining aquifer.
Current moratoria in the Platte Basin, which includes a moratorium
on new surface water diversions (NDNR 2008, entire), should prevent
current conditions from worsening throughout the most degraded portion
of the species' range along the central Platte River. Current State law
and management by the State's various natural resources districts on
the Loup and Elkhorn Rivers should maintain the groundwater table at
sustainable levels in those areas. For instance, the Loup and Elkhorn
River Basins are subject to limited surface water appropriations,
because the NDNR has to ensure adequate flows exist in the Lower Platte
Basin for endangered species, such as the pallid sturgeon (NDNR 2006,
p. E-11). Overall, we have determined that groundwater withdrawal does
not pose a threat to the species. However, additional stress from water
demand is likely to be placed on Nebraska's river systems in the future
as a result of climate change and projected increases in floods and
droughts (discussed below).
Climate Change
Global climate change is a concern, because it has the potential to
reconfigure the spatial distribution of species and their habitats
worldwide throughout the 21st century and beyond. Our analyses under
the Act include consideration of ongoing and projected changes in
climate. The terms ``climate'' and ``climate change'' are defined by
the Intergovernmental Panel on Climate Change (IPCC). The term
``climate'' refers to the mean and variability of different types of
weather conditions over time, with 30 years being a typical period for
such measurements, although shorter or longer periods also may be used
(IPCC 2007a, p. 78). The term ``climate change'' thus refers to a
change in the mean or variability of one or more measures of climate
(e.g., temperature or precipitation) that persists for an extended
period, typically decades or longer, whether the change is due to
natural variability, human activity, or both (IPCC 2007a, p. 78).
Scientific measurements spanning several decades demonstrate that
changes in climate are occurring, and that the rate of change has been
faster since the 1950s. Examples include warming of the global climate
system, and substantial increases in precipitation in some regions of
the world and decreases in other regions (IPCC 2007a, p. 30; Solomon et
al. 2007, pp. 35-54, 82-85). Results of scientific analyses presented
by the IPCC show that most of the observed increase in global average
temperature since the mid-20th century cannot be explained by natural
variability in climate, and is ``very likely'' (defined by the IPCC as
90 percent or higher probability) due to the observed increase in
greenhouse gas (GHG) concentrations in the atmosphere as a result of
human activities, particularly carbon dioxide emissions from use of
fossil fuels (IPCC 2007a, pp. 5-6 and figures SPM.3 and SPM.4; Solomon
et al. 2007, pp. 21-35). Further confirmation of the role of GHGs comes
from analyses by Huber and Knutti (2011, p. 4), who concluded it is
extremely likely that approximately 75 percent of global warming since
1950 has been caused by human activities.
Scientists use a variety of climate models, which include
consideration of natural processes and variability, as well as various
scenarios of potential levels and timing of GHG emissions, to evaluate
the causes of changes already observed and to project future changes in
temperature and other climate conditions (e.g., Meehl et al. 2007,
entire; Ganguly et al. 2009, pp. 11555, 15558; Prinn et al. 2011, pp.
527, 529). All combinations of models and emissions scenarios yield
very similar projections of increases in the most common measure of
climate change, average global surface temperature (commonly known as
global warming), until about 2030. Although projections of the
magnitude and rate of warming differ after about 2030, the overall
trajectory of all the projections is one of increased global warming
through the end of this century, even for the projections based on
scenarios that assume that GHG emissions will stabilize or decline.
Thus, there is strong scientific support for projections that warming
will continue through the 21st century, and that the magnitude and rate
of change will be influenced substantially by the extent of GHG
emissions (IPCC 2007a, pp. 44-45; Meehl et al. 2007, pp. 760-764, 797-
811; Ganguly et al. 2009, pp. 15555-15558; Prinn et al. 2011, pp. 527,
529). (See IPCC 2007b, p. 8, for a summary of other global projections
of climate-related changes, such as frequency of heat waves and changes
in precipitation. Also see IPCC 2011 (entire) for a summary of
observations and projections of extreme climate events.)
Various changes in climate may have direct or indirect effects on
species. These effects may be positive, neutral, or negative, and they
may change over time, depending on the species and other relevant
considerations, such as interactions of climate with other variables
(e.g., habitat fragmentation) (IPCC 2007a, pp. 8-14, 18-19).
Identifying likely effects often involves aspects of climate change
vulnerability analysis. Vulnerability refers to the degree to which a
species (or system) is susceptible to, and unable to cope with, adverse
effects of climate change, including climate variability and extremes.
Vulnerability is a function of the type, magnitude, and rate of climate
change and variation to which a species is exposed, its sensitivity,
and its adaptive capacity (IPCC 2007a, p. 89; see also Glick et al.
2011, pp. 19-22). There is no single method for conducting such
analyses that applies to all situations (Glick et al. 2011, p. 3). We
use our expert judgment and appropriate analytical approaches to weigh
relevant information, including uncertainty, in our consideration of
various aspects of climate change.
As is the case with all stressors that we assess, even if we
conclude that a species is currently affected or is likely to be
affected in a negative way by one or more climate-related impacts, it
does not necessarily follow that the species meets the definition of an
``endangered species'' or a ``threatened species'' under the Act. If a
species is listed as endangered or threatened, knowledge regarding the
vulnerability of the species to, and known or anticipated impacts from,
climate-associated changes in environmental conditions can be used to
help devise appropriate strategies for its recovery.
The effects of climate change, such as an increase in the global
average air surface temperature since 1970, are already being felt in
North America and around the world (U.S. Global Change Research Program
(USGCRP) 2009, pp. 9, 17). In the Rocky Mountains and Northern
Hemisphere, there has been a decrease in overall snowpack cover over
the past 100 years (IPCC 2007, p. 30), and the proportion of
precipitation falling as snow is decreasing (USGCRP 2009, p. 43). More
precipitation now falls in the form of extreme rain events (Rieman and
Isaak 2010, p. 4). A decrease in annual snowpack is projected to lead
to earlier spring snowmelt and runoff, reduced runoff and stream flow,
decreased recharge of
[[Page 52662]]
aquifers, an increase in drought frequency and intensity, and shorter
wetland hydroperiods (USGCRP 2009, p. 45; Johnson et al. 2010, p. 137;
Rieman and Isaak 2010, pp. 4, 6, 8). Flooding risk is also projected to
increase in association with warmer winters and earlier snowmelts
(Saunders and Maxwell 2005, p. 1), and summer flows are expected to be
lower (USGCRP 2009, p. 46). Decreases in the amount of snowfall and
earlier snowmelt in the Rocky Mountains are most likely to affect the
sloughs along the Platte River, because its flows are tied to Rocky
Mountain snowmelt, while Loup and Elkhorn River flows are tied to the
Ogallala Aquifer and local precipitation events.
In the Great Plains, the average annual temperature has increased
by 0.83 [deg]C (1.5[emsp14][deg]F) since the 1970s and is expected to
increase 2.5 [deg]C (4.5[emsp14][deg]F) by 2050 (USGCRP 2009, p. 123)
and between 4.2 [deg]C (8[emsp14][deg]F) and 5.0 [deg]C
(9[emsp14][deg]F) by the 2080s across the range of the Platte River
caddisfly (The Nature Conservancy 2007, entire). Should GHG continue at
the current rate, average annual precipitation is expected to remain
steady or decrease by 5 percent from today's levels across the range of
the Platte River caddisfly by 2050 (The Nature Conservancy 2007,
entire).
Between the 1930s and 2011, average maximum temperatures have
remained steady in the Lower Platte Basin (downstream of the North
Platte/South Platte confluence), while there has been an increase in
average maximum temperatures in the Upper Platte Basin (upstream of the
confluence) for the same time period (Stamm 2012, pers. comm.). During
the same time period, there has been a wetting trend in the Lower
Platte Basin and a drying trend in the Upper Platte Basin (Stamm 2012,
pers. comm.). Meanwhile, average minimum temperatures increased across
the entire Platte Basin between the 1930s and the decade ending in 2011
(Stamm 2012, pers. comm.). Available models for the Loup and Elkhorn
River Basins demonstrate similar trends (http://www.climatewizard.org/,
accessed June 25, 2012).
Should worldwide GHG emissions remain the same as today's levels,
starting in 2030, average temperatures are projected to increase
dramatically across the entire Platte Basin and continue increasing
through at least 2050, and precipitation is projected to remain steady
or decrease slightly compared to the decade ending in 2011 (http://www.climatewizard.org/, accessed June 25, 2012). Average winter,
spring, and fall temperatures are projected to increase by 1.0-2.5
[deg]C (2.7-4.5[emsp14][deg]F), and summer temperatures will likely
increase by 3.5-4.0 [deg]C (6.3-7.2 [deg]F) by 2050 when compared to
the decade ending in 2011 (http://www.climatewizard.org/, accessed June
25, 2012).
Compared to the decade ending in 2011, by 2030, fall and winter
precipitation is projected to remain steady or slightly decrease;
spring precipitation could decline by 20-30 mm, and summer
precipitation is projected to decrease by 50-60 mm for the Lower Platte
Basin (http://www.climatewizard.org/, accessed June 25, 2012).
Conditions are also expected to become hotter and drier in the Upper
Platte overall (http://www.climatewizard.org/, accessed June 25, 2012).
Because the sloughs along the Platte River receive snowmelt from the
Rocky Mountains (Williams 1978, p. 1) and there is anticipated to be
reduced snowpack, sloughs along the Platte River are likely to be more
vulnerable to drying than sloughs along the Loup and Elkhorn Rivers
during droughts.
Although some models indicate parts of the range of the Platte
River caddisfly could experience wetter winters and springs, projected
increases in temperature could negate the effects of increased
precipitation through increases in evaporation and transpiration
(evaporation of water from plant leaves), particularly in the summer
months (Sorenson et al. 1998, pp. 344-345, 355-356; Johnson et al.
2010, p. 128). Increased evapotranspiration (combined effect of
evaporation and transpiration) is expected to create drier conditions
in the northern Great Plains, thereby increasing the frequency and
severity of droughts (Sorenson et al. 1998, pp. 344-345; USGCRP 2009,
p. 126). Overall, by 2030, the entire area will likely be hotter and
drier compared to the decade ending in 2011 (Stamm 2012, pers. comm.).
A hotter and drier climate represents the worst-case scenario for the
Platte River caddisfly.
The Great Plains system is known for its extensive inter-annual
climate variability (Ojima et al. 1999, p. 1445), and episodic floods
and droughts are characteristic of prairie streams (Dodds et al. 2004,
pp. 205-206) where the Platte River caddisfly occurs. Species found in
Great Plains aquatic systems and in intermittent waters, such as the
Platte River caddisfly, are well-suited to survive these disturbance
events and environmental extremes (Lytle 2002, pp. 370, 371). However,
disturbances that occur outside the time when such events normally
occur could cause mortality to species such as the Platte River
caddisfly.
Despite the projected increase in the frequency of droughts,
projected increase in temperature, and projected decrease in
hydroperiod length, the Platte River caddisfly presumably survived
historical drought periods, particularly through the Dust Bowl (1930s).
In 2004, following a dry spring, the type locality for the caddisfly
was dry by early April, and adults were not found at that site in the
fall of 2004, despite consistent emergence in the 7 years prior
(Goldowitz 2004, p. 8). Platte River caddisfly adults were also not
observed during surveys between 2007 and 2009 (Riens and Hoback 2008,
p. 1; Vivian 2010, p. 48). In 2007 and 2009, the Platte River caddisfly
was not observed at one site near Shelton, Nebraska, following the
drought in central Nebraska in the early 2000s, and this site is still
presumed to be extirpated (Riens and Hoback 2008, p. 1; Vivian 2010, p.
48). Following wetter years in 2008 and 2009, the caddisfly was found
at the type locality in 2010 (Geluso et al. 2011, p. 1023), indicating
the species has the ability to recolonize suitable habitats following
disturbance events. Alternatively, Platte River caddisfly population
levels could have decreased to undetectable levels and then rebounded
following wetter conditions, as it is easy to miss individual adults
when conducting surveys in the autumn (Harner 2012, pers. comm.). It is
unknown if the species has recolonized the site near Shelton, Nebraska.
In normal years, the Platte River caddisfly is able to withstand
normal summer dry periods through aestivation (Whiles et al. 1999, p.
542). The burial behavior observed during the aestivation period in the
Platte River caddisfly lifecycle likely protects the species against
heat and desiccation (Geluso et al. 2011, p. 1024), and affords the
species added protection during extended droughts. Furthermore, the
related Ironoquia punctatissima (no common name) has been found to lay
its eggs in a gelatinous matrix on a dry streambed with the larvae
hatching once waters return (Clifford 1966, entire). It is unknown how
long the eggs of this species or the Platte River caddisfly could
survive without water, but this adaptation could provide the Platte
River caddisfly protection in years with shorter hydroperiods, if it
does exhibit this behavior. A shorter hydroperiod would likely be more
detrimental in the spring if a slough dried too early as it could
prompt the caddisfly to emigrate earlier from the aquatic environment,
possibly reducing the size of the larva
[[Page 52663]]
and overall fitness of the individual (Harner 2011, pers. comm.).
Recent modeling efforts demonstrated the potential effects of
shorter periods of slough inundation on the Platte River caddisfly.
Using long-term well data, Harner and Whited (2011, entire) created a
model that demonstrated that during a dry period in the record (2000-
2003), the type locality slough held water for approximately 249 days,
whereas during a wet period (1997-1999), the slough was wet for
approximately 340 days (Harner and Whited 2011, p. 21). Most of this
drying occurred in summer and fall, and adults were observed in 2003.
Larvae were also present at the type locality in the spring of 2004;
however, the slough dried more than 2 months earlier in 2004 than what
had been observed in years prior, and adults were not observed in the
autumn of 2004 (Goldowitz 2004, p. 9). Therefore, droughts that result
in sloughs drying too early would likely be more detrimental to the
caddisfly than prolonged drying into the autumn and could lead to
localized extirpations.
Drought has been implicated in at least the temporary loss of two
Platte River caddisfly populations, one of them being the formerly
robust type locality. Following the drought, the caddisfly is now again
present at the type locality (Geluso et al. 2011, p. 1024) and possibly
could have migrated downstream to a more permanent portion of the
slough during the extended drought of the early 2000s (Vivian 2011,
pers. obs.). Also, the type locality and population near Shelton,
Nebraska, occur farther away from the main channel of the Platte River;
these areas are less likely to withstand droughts than sloughs closer
to the main channel, because hydroperiod decreases with increasing
distance from the river (Whiles et al. 1999, p. 533). Throughout the
rest of the range of the Platte River caddisfly, historical aerial
imagery from 2003-2006, a period of drought, indicates that the
remaining 33 sloughs where the caddisfly is known to occur likely held
enough water to support the caddisfly (Vivian 2012, pers. obs.). Thus,
it appears that the recent drought had localized effects on a few
populations but was not an issue across the range of the species.
Hotter and drier summers in the future are likely to result in
increases in evapotranspiration, which may also lead to drier soil
conditions (Sorenson et al. 1998, p. 344; Johnson et al. 2010, p. 134),
and these conditions could impact aestivating caddisfly larvae in areas
with an open canopy. However, most caddisfly populations occur in
sloughs surrounded by a forest canopy, and this shade cover is likely
to provide some protection against evaporative losses from soil and
reduce the risk of desiccation (Vivian 2009-2010, pers. obs). The
distribution and habitat of the Platte River caddisfly likely confer
added protection for the species during times of drought and future
climatic extremes. For instance, the species is known from the Platte,
Loup, and Elkhorn Rivers, and the Loup and Elkhorn Rivers are tied more
to groundwater inputs than snowmelt and precipitation. However, the
sloughs along all three river systems are tied to groundwater levels to
some degree, and groundwater-fed wetlands are thought to be less
vulnerable to climate change than those more tied to inputs of
precipitation (Winter 2000, p. 308). Because the caddisfly: (1)
Presumably survived the Dust Bowl, a period of extreme dryness on the
magnitude expected by climate change; (2) exhibits behaviors that
enable it to survive extended dry periods; (3) spans a large geographic
area that encompasses a range of annual average precipitation; and (4)
is present in more than one habitat type across its range, including in
areas that maintain water during droughts, we have determined that
habitat impacts associated with climate change do not pose a threat to
the caddisfly throughout its range.
Flooding
The frequency and intensity of floods are projected to increase
with the onset of climate change (Saunders and Maxwell 2005, p. 1).
However, flooding is not likely to pose a significant threat to the
Platte River caddisfly and could be of some benefit. Flooding events
can scour aquatic organisms downstream in some systems (Feminella and
Resh 1990, p. 2083), but the velocity at which Platte River caddisfly
larvae are moved downstream is unknown. The caddisfly may not be
subject to scouring flows, because it is found in lentic waters.
Ironoquia punctatissima survives flood events with discharges of 100
cm/s by seeking refuge in tangled grass roots (Williams and Williams
1975, p. 829), and the Platte River caddisfly may exhibit similar
behavior. It has also been recognized that the hyporheic zone
(saturated subsurface region, area where groundwater and surface water
mixing occurs (del Rosario and Resh 2000)) can be important in the
recolonization of benthic macroinvertebrates following flood events
(Williams and Hynes 1974, p. 234; Williams and Hynes 1976, p. 266;
Boulton et al. 1998, p. 64), and the Platte River caddisfly has been
found within the hyporheic zone in all five instar stages (Whiles et
al. 1999, p. 535; Vivian 2010, pers. obs.). After high water in May to
June 2010, which is during the terrestrial stage of the Platte River
caddisfly lifecycle, several live individuals were found along the
slough banks at two sites immediately after flood waters had receded
(Vivian 2010, p. 52). The burial behavior observed in the Platte River
caddisfly may protect a certain portion of terrestrial larvae from late
spring floods (Geluso et al. 2011, p. 1024).
Even if mortality of larvae were to occur due to scouring, flooding
is likely important in the creation of backwater habitats and the
subsequent increase in habitat availability to the Platte River
caddisfly. Downstream larval drift is considered an important means of
dispersal (Neves 1979, p. 58), but only in habitats that are connected
by water (Petersen et al. 2004, p. 934). Caddisflies found in isolated
habitats or pools are more likely to disperse via flight than by
downstream larval drift, because these habitats are not connected
(Williams 1996, p. 644; Petersen et al. 2004, p. 934). Some inhabitants
of temporary wetlands may be strong fliers, such as some limnephilids
(Svensson 1974, p. 174); however, observations conducted during the
adult life stage suggest the Platte River caddisfly is a weak flier
(Vivian 2010, p. 39). An increase in habitat availability due to
flooding may increase the chances for the species to colonize new
populations and link up areas of suitable habitat. Overall, flooding
could increase the amount of suitable habitat for the Platte River
caddisfly, and this would likely benefit the species. Because of
various behaviors exhibited by the Platte River caddisfly that likely
enable it to withstand flooding events, we do not consider flooding or
the projected increase in flooding to pose a threat to the caddisfly.
Wetland Conversion and Modification
As previously mentioned, historical water development in the Platte
Basin contributed to a decline in the active floodplain, and opened up
former wet bottomlands for crop development (Currier et al. 1985, p.
113). Active efforts to drain wetlands to make an area suitable for row
crops also historically contributed to wetland habitat loss, and there
has been an estimated 73.5 percent loss of meadows within 3.5 miles of
the Platte River as a result of channel narrowing and conversion for
agriculture (Currier et al. 1985, p. 119). As of 1911, approximately
1.5 million acres of grassland had been converted to row crops in the
Platte Valley (Currier et al. 1985, p. 113). Agriculture, including the
production of row crops,
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is the predominant land use in Nebraska, and in recent years, a rise in
ethanol production has led to an increase in grain prices, which in
turn has led to an increase in the number of acres of corn planted in
Nebraska (Nebraska Corn Board 2011, entire). Currently, the United
States produces around 13 billion gallons of ethanol annually, but the
Energy Independence and Security Act of 2007 (42 U.S.C. 17001 et seq.)
mandates that this number increase to 36 billion gallons by 2022.
Increases in the world's population also will likely lead to an
increase in the demand for grain, and, in Nebraska, increasing grain
production is contributing to a decline in grassland habitat.
Concurrent with the increase in the planting of more acres of corn
in Nebraska, ongoing wetland modification may result from the
conversion of adjacent grasslands to row crops at a limited number of
sites. In 2011, we consulted with the NRCS on approximately 70
sodbuster applications received from Nebraska landowners. Sodbuster
applications are submitted by individuals who desire to convert highly
erodible grassland into crop production. The increase in sodbuster
applications demonstrates that grassland habitats are continually
vulnerable to the development of row crops.
The Platte River caddisfly was discovered in a large, grassland
complex. At the type locality and Wild Rose Slough, the caddisfly uses
adjacent grassland habitat in which to aestivate and complete adult
emergence. However, most Platte River caddisfly populations occur in
forested sloughs adjacent to the main river channel, and these areas
are thought to be buffered against conversion into row crops. Sloughs
adjacent to the river also appear to be too deep to be suitable for
filling and conversion for agriculture, and these sloughs are also
protected from fill under the U.S. Army Corps of Engineers (Corps) 404
program (discussed under Factor D). Therefore, there is not likely to
be much overlap between the ongoing conversion of grassland into corn
and Platte River caddisfly habitat. As a result, we do not consider
wetland conversion to constitute a threat to the species.
Wetland Restoration
Several nongovernmental organizations (NGOs) are actively restoring
degraded wetlands in the central Platte region (Whiles and Goldowitz
2005, p. 462); however, restored wetlands often do not equal natural
wetlands in terms of floral and faunal diversity (Galatowitsch and van
der Walk 1996, entire). Differences in wetland hydrology between
natural and restored wetlands can affect the outcomes of restoration
projects (Galatowitsch and van der Walk 1996, entire; Meyer and Whiles
2008, entire). For instance, in central Nebraska, it has been shown
that some aquatic taxa are missing entirely from restored sloughs as
compared to natural sloughs (Meyer and Whiles, 2008, entire).
Restored wetlands, although beneficial in providing habitat for
some species, may not immediately provide suitable habitat for the
Platte River caddisfly. Between 2009 and 2010, 12 restored sloughs were
surveyed for the Platte River caddisfly, and only one slough had
evidence of caddisfly presence (Vivian 2010, p. 46). One discarded case
was found at this site, and it is unknown whether there is an extant
population at this location, as no live individuals were found (Vivian
2010, p. 17). When surveyed, restoration work had occurred 4 years
prior to the survey (Schroeder 2011, pers. comm.), and it is unknown if
the caddisfly was present before the restoration work had occurred. One
other restored slough on Crane Trust property was previously found to
support the Platte River caddisfly, but the site supported a low number
of individuals. This site was near the type locality (Meyer and Whiles
2008, p. 632; Meyer 2009, pers. comm.), which may represent a source
population. These observations suggest that restored sloughs may not be
immediately suitable to the caddisfly but could become more suitable
over time as the restored sloughs become established.
To date, only one restoration project is known to have resulted in
adverse impacts to the Platte River caddisfly. At Bader Park near
Chapman, Nebraska, a 2007 restoration project within a slough where the
caddisfly was known to occur resulted in a decline in larval densities
at that site (Harms 2009, pers. comm.). The caddisfly still occurs at
that site, but at a density of less than one individual per m\2\
(Vivian 2010, p. 64), possibly because the slough now harbors various
fish species that were not present before the restoration activities
occurred. Since the Bader Park project, the Service has drafted
guidelines to avoid adverse impacts to the caddisfly while conducting
restoration work in sloughs where the species occurs. Overall, we think
that restoration projects, if conducted with the Platte River caddisfly
in mind, could provide benefits to the caddisfly in terms of an
increase in the amount of available habitat, particularly in the long
term. Thus, we have determined that wetland modification done as a part
of restoration work does not pose a threat to the Platte River
caddisfly.
Urbanization and Infrastructure
It is likely that urbanization of the Platte River valley has
impacted the habitat of the Platte River caddisfly in the past. For
instance, 14 bridges span the North Platte and Platte Rivers between
Chapman, Nebraska, and Lewellen, Nebraska, a distance of about 380 km
(240 mi) (Currier et al. 1985, p. 56). Bridge construction can result
in localized channel narrowing, because sediments get deposited
upstream of the bridge site, and scour occurs downstream of the bridge
site for at least a half-mile (Simons and Associates 2000, p. 67).
Underneath bridges, channel incision may occur, leading to the
degradation of adjacent wetlands as incision can lead to drawdowns of
alluvial aquifers (Kondolf 1997, p. 542). Bridge choke points (areas
immediately upstream and downstream of bridges where the river has
narrowed) can also become open to sandpit development following channel
narrowing.
Beginning in the 1980s, the Federal Highway Administration (FHWA)
implemented new requirements for bridges to prevent the encroachment of
bridge embankments into river channels (Murphy et al. 2004, p. 52).
Therefore, any present and future bridge projects are required to allow
for sufficient room for a river to migrate and create and maintain
backwater habitats. Ongoing effects to Platte River caddisfly habitat
can be expected at bridge choke points, because no new habitat is being
created in those areas. Recently, FHWA contacted the Service to
coordinate ways to avoid and minimize impacts to slough habitat during
a bridge project at Fullerton, Nebraska. No survey for the Platte River
caddisfly has been conducted at that site, but coordination with FWHA
demonstrates that potential adverse impacts on the caddisfly resulting
from current and future bridge projects can be avoided. For bridge
projects and other projects that are federally funded or authorized,
the Service has the opportunity and does provide comments to addresses
any concerns to listed species, candidate species, and species of
concern, such as the Platte River caddisfly (see Factor D).
Along Interstate 80, several sandpit lakes were created to extract
gravel used for interstate construction in the 1960s (Currier et al.
1985, p. 70); these past operations have been linked to wetland losses
along the Platte River (Sidle et al. 1989, p. 99). Many of these areas
now support housing developments adjacent
[[Page 52665]]
to the river, and these developments further confine the river to its
banks through bank armoring, which reduces the ability of the river to
create new channels and backwater areas (Schramm et al. 2008, p. 238),
which are important habitat for the caddisfly. The construction of
Interstate 80 has also contributed to a large amount of direct wetland
losses north of the Platte River as the interstate runs within 0.25
mile of the river for over 100 miles in Nebraska (Currier et al. 1985,
p. 122).
Bank stabilization and armoring projects constructed to protect
property against erosion can also cause the localized scouring of a
river channel and have the potential to lead to the drying of adjacent
wetlands. Bank stabilization efforts, particularly under the Corps'
nationwide permitting process, are ongoing throughout Nebraska and have
the potential to impact occupied sloughs. However, only one of 35 sites
with the caddisfly is currently adjacent to a bank stabilization
project, and this site is just upstream of a bridge and does not appear
to be degrading the quality of the slough (Vivian 2009, pers. obs.). We
have no evidence to indicate that bank armoring along the Platte, Loup,
and Elkhorn Rivers is occurring at a large enough scale to adversely
impact the caddisfly and its habitat. We do not know of any current or
future bank stabilization projects that are scheduled to occur near
areas where the caddisfly has been found. Most Platte River caddisfly
populations are considered to be protected from bank armoring projects,
as 21 out of 35 sites with the caddisfly occur on protected lands.
Overall, most impacts from urbanization and infrastructure projects
largely occurred in the past and are localized in their effects. Since
the Platte River caddisfly was described in 2000, there is no available
information that suggests any habitat losses as a result of bridge
construction, road, sandpit, or bank armoring development have
occurred. We are not aware of planned projects within caddisfly
habitat, and therefore we conclude that urbanization and infrastructure
are not likely to pose threats to the Platte River caddisfly.
Livestock Grazing
The Platte River caddisfly and its habitat could be adversely
impacted by some cattle grazing regimes. Cattle have a strong affinity
for riparian areas because of the availability of water, shade, and
high-quality forage (Kauffman and Krueger 1984, p. 431). Cattle can
impact wetlands through the reduction of vegetation cover along wetland
bottoms and shorelines, increased sedimentation and erosion, increased
nutrient and organic inputs from urine and manure, increased water
temperatures, and degraded water quality, particularly when cattle have
unrestricted access to streams (Schulz and Leininger 1990, pp. 297-298;
Fleischner 1994, pp. 631-636; Evans and Norris 1997, p. 627; Downes et
al. 2000, p. 569; Braccia and Voshell 2006a, p. 269; Braccia and
Voshell 2006b, p. 2). A reduction in vegetation cover can lead to
decreases in the inputs of coarse particulate organic matter on which
the Platte River caddisfly feeds (Kauffman and Krueger 1984, p. 43;
Braccia and Voshell 2006a, p. 269). Despite potential impacts, we have
no evidence that the species is currently being adversely affected by
cattle grazing to the point that grazing would contribute to localized
extirpations. Cattle grazing occurs at or adjacent to 6 of 35 Platte
River caddisfly sites, and there is no evidence of grazing occurring
directly in the sloughs (Vivian 2010, pers. obs.). Also, Wild Rose
Slough, which is one of the six sites where grazing occurs, supports
the largest known caddisfly population.
A study conducted at Wild Rose Slough to investigate the effects of
grazing on the Platte River caddisfly found vegetation productivity to
be lower in grazed plots than in ungrazed plots 6 months following the
removal of cattle from the study site in spring 2010 (Harner and Geluso
2012, p. 391). In September 2010, fewer adult caddisflies were observed
in grazed plots than in ungrazed plots, and in 2011, lower densities of
aquatic caddisfly larvae were found in grazed plots than in ungrazed
plots (Harner and Geluso 2012, pp. 391-392). Meanwhile, a positive
relationship between vegetation productivity and larval densities was
observed (Harner and Geluso 2012, pp. 391-392).
Results from the cattle grazing study demonstrated that although
cattle were not allowed access to the study area in 2011, the effects
of grazing on caddisfly larval densities could still be observed up to
one year after grazing occurred (Harner and Geluso 2012, p. 392). These
data also suggest that reduced vegetation cover contributed to
decreased larval densities in intensely grazed areas within the study
plots (Harner and Geluso 2012, p. 392). However, because larvae were
not eliminated in grazed areas, this study demonstrates that intense
grazing may not be detrimental to the caddisfly for short time periods
or under a rotational grazing regime (Harner and Geluso 2012, p. 392)
and that this species can likely withstand moderate amounts of grazing,
particularly at sites where larval densities are relatively high.
Continuous grazing in areas where the caddisfly is less abundant could
contribute to localized extirpations, and the caddisfly has not been
found at sites that show signs of intense grazing (e.g., more than 40
percent of the bank exposed) (Braccia and Voshell 2006a, p. 271; Vivian
2010, p. 52). However, none of the six sites with the Platte River
caddisfly where grazing occurs show signs of overgrazing (Vivian 2010,
pers. obs.). Therefore, we have determined that grazing is not likely
to pose a threat to the caddisfly.
Pesticides and Herbicides
Corn and soybean fields dominate the river valleys of Nebraska, and
both represent potential sources of pesticide exposure to the Platte
River caddisfly and its habitat. Should insecticides and herbicides
enter occupied habitats of the Platte River caddisfly through runoff,
they have the potential to directly impact the species through
mortality or indirectly through mortality of aquatic vegetation in the
aquatic environment (Fleeger et al. 2003, entire; Liess and Von Der Ohe
2005, entire). Pesticides also may enter wetlands through groundwater
inputs and could affect aquatic organisms (Spalding et al. 2003, p.
92). Surfactants designed to facilitate pesticide and herbicide
application have also been shown to have direct and indirect effects on
caddisfly larvae (Belanger et al. 2000, entire; Fleeger et al. 2003,
entire, respectively).
There have been no studies to evaluate the potential effects of
pesticide exposure on the Platte River caddisfly. Past studies have
demonstrated mortality in other species of caddisflies exposed to
pesticides (Liess and Schulz 1996, entire) and documented the absence
of caddisflies from polluted waters (Ketelaars and Frantzen 1995,
entire). Reduced abundances of aquatic insect species considered
sensitive to poor water quality have been observed in habitat adjacent
to agricultural areas (Liess and Von Der Ohe 2005, entire) that would
presumably contain pesticide runoff.
Aside from agricultural runoff, one potential source of herbicides
in Platte River caddisfly habitat is chemicals used for the control of
exotic vegetation, such as Phragmites. Because of the establishment of
Phragmites along the Platte River, efforts have been taken to control
the invasive vegetation using herbicide application. In 2009, the
aquatic-safe herbicide Habitat[supreg] was sprayed in areas with
Phragmites in the main channel of the Platte River (The
[[Page 52666]]
Nature Conservancy 2011, entire), and it is possible that drift could
cause Habitat[supreg] to enter sloughs where the caddisfly occurs.
Habitat[supreg] may result in lower amounts of dissolved oxygen in
sloughs as a result of plant decomposition (BASF[supreg] 2010, entire).
Some spraying for Phragmites occurred in 2009, during the early autumn
when Platte River caddisfly adults are active (Vivian 2009, pers.
obs.). Lower amounts of dissolved oxygen could impact developing
caddisfly eggs or reduce the amount of potentially important shade
cover in areas where willow (Salix spp.) co-occurs with Phragmites
(Vivian 2010, pers. obs.).
Despite potential adverse impacts to the caddisfly, there is no
evidence that population declines or extirpations have occurred as a
result of pesticide or herbicide exposure. Following the spraying of
Phragmites in 2009, the Platte River caddisfly was found again at three
of three sites where overlap between spraying and habitat occurred.
Most Platte River caddisfly populations are also likely protected from
pesticide or herbicide exposure by sufficient buffer strips. For
instance, two populations located adjacent to or very near cornfields
are likely protected from runoff by a tree and grass buffer of at least
40 meters (131 feet), as the larval densities at these two sites are
among the highest of known populations. The 21 populations that occur
on protected lands are likely protected from most spray activities
typically associated with agriculture. Furthermore, the caddisfly
lifecycle likely protects it from some pesticide exposure, because
larvae have been observed emigrating from the water as early as mid-
April before most crops are in the ground, and the majority of
pesticides would enter waterways during the typical farming season in
Nebraska of May through October.
Local Conservation Planning
In addition to existing regulatory mechanisms and provisions
(discussed under Factor D, below), 60 percent (21 of 35) of Platte
River caddisfly populations occur on nongovernmental organization or
State lands that are protected for conservation or managed as
wilderness areas. These conservation efforts may afford protection of
Platte River caddisfly habitat now and into the future. Such examples
include Nebraska's Wildlife Management Areas (WMAs) and land owned and
managed by the Headwaters Corporation, the group responsible for
implementing and overseeing PRRIP. To date, Headwaters has been
involved in several discussions with the Service on ways to avoid
adverse impacts to the caddisfly with projects in and near Platte River
caddisfly habitat. Currently, three Platte River caddisfly populations
occur on Headwaters lands, and these sites are likely to be protected
from future development by way of a conservation easement. Two other
populations occur along roadsides in areas managed by the Nebraska
Department of Roads (NDOR), and the Service works with NDOR to avoid
and minimize impacts to wetlands on road projects.
The Crane Trust is another entity whose lands provide protection
for the Platte River caddisfly. The Trust manages 10,000 acres of land
in the central Platte region that have been set aside for wildlife in
perpetuity. Four Platte River caddisfly populations are known to occur
on land owned by the Crane Trust, and these sites support the largest
Platte River caddisfly larval densities currently known. In addition,
two Platte River caddisfly populations occur on land owned by The
Nature Conservancy (TNC), and the organization is aware of these
populations and has taken measures to avoid adverse impacts to the
species at these sites.
In areas not protected for conservation, many agencies and
organizations have been kept apprised of the Platte River caddisfly and
have been engaged with the Service on ways to avoid and minimize
impacts to the species and its habitat. For instance, the Federal
Highway Administration has coordinated with the Service on ways to
avoid and minimize impacts during a bridge reconstruction project near
potentially suitable habitat (where the caddisfly was thought to occur)
near Fullerton, Nebraska (Vivian 2010, pers. obs.). Also, PFW has noted
they are willing to consider the Platte River caddisfly in their
wetland restoration work that occurs on public and private lands
(Schroeder 2012, pers. comm.). In 2011, PFW and TNC involved the
Service in discussions on how to avoid adverse impacts to the caddisfly
during restoration work at a site on TNC property. In 2010, the
Service's Nebraska Field Office held a workshop for personnel from
various local, State, and Federal agencies and organizations on the
Platte River caddisfly, its habitat, and survey methodology. This
workshop equipped agencies outside the Service with the knowledge to be
able to avoid impacts to the caddisfly and its habitat.
PRRIP is a program that affords the Platte River caddisfly
protection now and into the future throughout the most degraded portion
of its range. Objectives of PRRIP that may benefit the Platte River
caddisfly include: (1) Preventing the need to list more basin-
associated (Platte River) species under the Act; (2) offsetting through
mitigation any adverse impacts of new water-related activities on
Service-targeted flows in the Platte River basin (target flows are
comprised of species flows and annual pulse flows, which have been
identified as flows needed to maintain survival of four target species
and wildlife that use the Platte River, and to maintain present channel
width and keep islands unvegetated (USDOI 2006, pp. 3-11, 3-12)); (3)
using available resources to manage program lands for the benefit of
non-listed species of concern, like the Platte River caddisfly; (4)
providing sufficient water in the central Platte River (Lexington,
Nebraska to Chapman, Nebraska) for the benefit of PRRIP's target
species (whooping crane, Interior least tern, piping plover, pallid
sturgeon) through water conservation projects; and (5) protecting and
restoring 29,000 acres of habitat in the central Platte River for the
benefit of the four target species (USDOI 2006, pp., 1-3, 1-17). This
agreement was put in place to specifically benefit other endangered and
threatened species, but should help maintain the backwaters where the
Platte River caddisfly occurs, particularly through PRRIP's goal of
maintaining current flows in the central Platte River.
Overall, existing programs and organizations that manage land for
conservation provide adequate protection for the species and its
habitat. Proactive planning efforts with Federal, State, and local
agencies, as well as nongovernmental organizations, also help to avoid
and minimize impacts to the caddisfly.
Summary of Factor A
Changes in hydrology resulting from water development and its
associated effects, including channel degradation and narrowing,
invasive species encroachment, urbanization, cropland conversion,
groundwater withdrawal, cattle grazing, climate change, pesticides, and
floods and droughts, all occur or are likely to occur within the range
of the Platte River caddisfly. These environmental stressors will
likely continue in the future on each of the river systems where the
Platte River caddisfly is known to occur. However, while these
stressors are ongoing, when considered individually and collectively,
we have determined that they do not pose a threat to the Platte River
caddisfly.
The Platte River caddisfly has life-history traits that enable it
to survive in an extreme environment, such as the
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Great Plains, where climatic extremes are common. These traits are
common among species that inhabit temporary (intermittent or ephemeral)
wetlands and enable these species to adapt relatively quickly to
changing conditions. The Platte River caddisfly can withstand habitat
drying, drought, and flooding by burrowing in the soil, aestivating
during a time when its habitat is most likely to go dry, inhabiting the
hyporheic zone, and possibly laying its eggs in the absence of water
(like Ironoquia punctatissima). These life history traits likely render
the Platte River caddisfly well-suited to withstand future climatic
changes.
We also conclude that the aforementioned stressors do not pose a
threat to the species, because the Platte River caddisfly occurs in
more than one habitat type and on multiple river systems. Surveys have
shown that the caddisfly occupies intermittent and permanent sloughs,
forested sloughs, and sloughs with an open canopy. While the type
locality and intermittent sloughs most likely represent ideal Platte
River caddisfly habitat, the species is found in permanent sloughs, and
these may be important during times of drought, as they are likely to
hold water longer and serve as a refuge during extended dry periods.
Forested canopies may offer an additional source of protection against
a warmer and drier climate.
Currently, available information does not indicate whether Platte
River caddisfly population levels are increasing or decreasing, or if
the amount of potential habitat is increasing or decreasing. Overall,
we have documented that the species is more common than previously
thought and likely is more abundant now than during the drought in the
early 2000s. Also, an increase in surveys is likely to result in an
increase in the known range of the caddisfly, given the amount of
potential habitat that has yet to be surveyed. Additional survey work
would likely result in populations being found on more river systems,
such as the Cedar, Niobrara, and Republican Rivers in Nebraska.
Currently, the Platte River caddisfly is known from three river
systems, and most of the potential threats occur along the Platte
River. Historically, the species likely occupied a much greater portion
of the Platte River than today. However, despite all of the water
development that has occurred on the Platte River system, the caddisfly
still occurs along the majority of the reach surveyed between 2009 and
2011. While ongoing degradation poses a threat to the river and the
remaining slough habitat available to the caddisfly, several agencies
and nongovernmental entities are working to stem future habitat losses.
Therefore, conditions are not anticipated to deteriorate on the Platte
River, and we consider the majority of caddisfly populations on the
river to be secure.
Currently, the Loup and Elkhorn Rivers have less water development
and are less degraded than the Platte River, and the best available
information indicates that there is sufficient habitat available
(including sloughs not yet surveyed) to sustain the Platte River
caddisfly on these systems. Future changes to these river systems are
anticipated to occur through increasing sodbusting activities and
groundwater withdrawal; however, these activities have little overlap
with Platte River caddisfly habitat, and current laws and regulations,
such as Nebraska State law LB 962, limit the extent to which this can
occur.
After a review of the best available information, we have
determined that the present or threatened destruction, modification, or
curtailment of its habitat or range does not pose a threat to the
Platte River caddisfly.
Factor B. Overutilization for Commercial, Recreation, Scientific or
Educational Purposes
There is no indication that the Platte River caddisfly is being
over collected by hobbyists or researchers, or will be in the future.
Collecting of Platte River caddisfly larvae has occurred for scientific
purposes (e.g., identification, museum archiving, lab experiments, and
genetic analyses), but this has been limited, and largely done at sites
supporting the greatest densities of the insect (Alexander and Whiles
2000, p. 1; Vivian 2010, pp. 74-77; Geluso et al. 2011, p. 1022;
Cavallaro et al. 2011, p. 5). The caddisfly is not known to have been
collected for educational purposes.
Insect collectors have not been known to take Platte River
caddisfly adults for their collections, likely because caddisfly adults
are not as showy as other groups of insects, such as butterflies. Also,
caddisfly adults are active during a narrow window (i.e., 3 weeks), and
the sites where the species occurs are isolated from urban areas and
difficult to access.
Summary of Factor B
There is no evidence that overutilization presents a threat to the
Platte River caddisfly. Although small, isolated collections of larvae
will likely continue for research purposes, we have determined that
these collections do not constitute a threat to the species because, to
date, these collections have only been conducted at sites with
relatively high larval densities. Therefore, we conclude that the best
scientific and commercial information available does not indicate that
overutilization for commercial, recreational, scientific, or
educational purposes is a threat to the Platte River caddisfly.
Factor C. Disease or Predation
Disease and predation play important roles in the natural dynamics
of populations and ecosystems. Natural predators of the Platte River
caddisfly evolved in conjunction with the caddisfly and do not normally
pose a threat to the survival of the species in the absence of other
threats. The Platte River caddisfly could be a prey item for predators
that are commonly observed in its habitat during its aquatic,
terrestrial, and adult stages. Predators of caddisflies in temporary
habitats may include large aquatic insects (dragonflies, beetles),
amphibians (frogs, salamanders) (Batzer and Wissinger 1996, entire;
Wellborn et al. 1996, entire), or fish, particularly in more permanent
wetlands (Wissinger et al. 1999, entire). Aquatic insects, amphibians,
and several fish species have all been observed at sites with the
Platte River caddisfly, but the sand-grained case of the Platte River
caddisfly likely offers it some protection from predators in its
environment, as larvae in mineral cases can better withstand crushing
than larvae in cases composed of organic material (Otto and Svensson
1980, p. 857).
Despite having mineral cases that can withstand crushing, the brook
stickleback (Culaea inconstans) readily consumed Platte River caddisfly
larvae in a laboratory setting, typically after the fish removed the
larvae from their cases (Cavallaro 2011, pers. comm). The brook
stickleback has been found to reduce macroinvertebrate biomass in
wetlands in the Western Boreal Forest (Hornung and Foote 2006, entire),
and the brook stickleback has been found at five sites with the Platte
River caddisfly, but these sites do not support markedly lower
densities of the Platte River caddisfly. Also, the caddisfly is well
camouflaged in its environment, and field trials have not been
conducted to determine if the brook stickleback consumes the Platte
River caddisfly in its natural environment. Furthermore, the brook
stickleback has been collected upstream and downstream of the central
Platte River since 1942, and from the central Platte River since 1987
and possibly earlier (Chadwick et al. 1997, p. 285), and the fish is
considered native to
[[Page 52668]]
Nebraska (Fischer and Paukert 2008, pp. 372-373). Therefore, the
caddisfly and stickleback have likely overlapped in their ranges prior
to the discovery of the Platte River caddisfly, and there is no
available information to indicate that brook sticklebacks have
contributed, or are contributing, to localized extirpations of the
caddisfly.
In addition to the brook stickleback, the Platte River caddisfly
has been found to occur with other fish predators, including the redear
sunfish (Lepomis microlophus), fathead minnow (Pimephales promelas),
common carp (Cyprinus carpio), and largemouth bass (Micropterus
salmoides) (Vivian 2011, p. 14). However, there is no indication that
these fish predators are resulting in population declines at these
sites or that these sites support lower densities of the Platte River
caddisfly compared to sites without these predators. Therefore, we
conclude that predation during the aquatic stage does not pose a threat
to the Platte River caddisfly.
The Platte River caddisfly is likely impacted by predation in its
terrestrial larval and adult stages. Several caddisfly cases have been
recovered that show signs of predation possibly by ants or beetles and
small mammals, such as shrews. Signs of predation include tears in the
cases or holes at the posterior end of the case (Vivian 2009, pers.
obs.). However, the sand-grained larval case likely offers some
protection to terrestrial larvae through camouflage and defense against
crushing (Otto and Svensson 1980, p. 857). Adults are likely eaten by
migratory birds and waterfowl (Whiles et al. 1999, p. 543). At sites
with relatively low numbers of caddisflies, predation on larvae in the
terrestrial stage and adults could pose a threat to this species in the
future. However, there is no available evidence that the predation of
terrestrial larvae or adults is impacting populations of the Platte
River caddisfly. Therefore, we do not consider predation during the
terrestrial larval and adult life stages to constitute a threat to the
species.
Given the small number of individuals at some sites, it is possible
that disease could pose a threat to the Platte River caddisfly.
However, we have no evidence to suggest that any disease is currently
affecting the Platte River caddisfly.
Summary of Factor C
Although the Platte River caddisfly is likely a prey item for
various predators (native and non-native), there is no evidence that
suggests current levels of predation or disease on the Platte River
caddisfly are currently affecting populations or will in the future.
Therefore, we conclude that the best scientific and commercial
information available indicates that neither disease nor predation
poses a threat to the Platte River caddisfly.
Factor D. Inadequacy of Existing Regulatory Mechanisms
Existing Federal, State, and local laws; regulations; and policies
that may provide a moderate level of protection for the Platte River
caddisfly and its habitat include: The National Environmental Policy
Act (NEPA; 42 U.S.C. 4321 et seq.), the Fish and Wildlife Coordination
Act (FWCA; 16 U.S.C. 661 et seq.), section 404 of the Clean Water Act
(CWA; 33 U.S.C. 1251 et seq.), and Nebraska State law LB 962.
For all federally funded or authorized projects, Federal actions,
or projects occurring on Federal lands, an Environmental Assessment or
Environmental Impact Statement is required under NEPA. NEPA is a
procedural statute that requires federal agencies to consider the
environmental impacts of a proposed project and reasonable alternatives
to project actions. It also requires full disclosure of all direct,
indirect, and cumulative environmental impacts of the project. However,
NEPA does not require protection of a particular species or its
habitat, nor does it require the selection of a particular course of
action. Therefore, NEPA may only provide a limited amount of protection
to the caddisfly in situations where NEPA was applicable.
NEPA does not apply to non-Federal projects on private lands or
privately funded projects, and about 34 percent (12 of 35 sites) of the
known populations of the Platte River caddisfly occur on private lands
or near road ditches. Projects occurring on public hunting grounds or
access areas, land under the management of conservation groups, and
roadsides often receive Federal dollars, and, therefore, NEPA would
apply to 66 percent of sites with the Platte River caddisfly. However,
as stated above, NEPA does not provide protection to species. There is
no available information regarding any development projects, private or
otherwise, occurring within Platte River caddisfly habitat. Overall, we
conclude that NEPA would provide some protection to the Platte River
caddisfly in the event that development projects and slough habitat
overlap in the future.
FWCA requires that proponents of Federal water development
projects, including those involving stream diversion, channel
deepening, impoundment construction, and/or general modifications to
water bodies, consider their impacts to fish and wildlife resources.
FWCA also requires that impacts to water bodies be offset through
mitigation measures developed in coordination with the Service and the
appropriate State wildlife agency. FWCA would provide adequate
protection to the Platte River caddisfly in the event that water
development projects and Platte River caddisfly habitat overlap.
However, there is currently no information regarding any current or
planned water development projects within the range of the Platte River
caddisfly. Should future water development projects occur within Platte
River caddisfly habitat, we have determined that FWCA would adequately
protect the caddisfly and its habitat, because the Service would be
provided an opportunity to address potential concerns with fish and
wildlife resources, including the caddisfly.
The U.S. Army Corps of Engineers (Corps), acting under the
authority of section 404 of the CWA, regulates the placement of fill
materials into waters under Federal jurisdiction, including the filling
of wetlands. Historically, according to a 1977 Corps definition, waters
under Federal jurisdiction applied to ``waters of the United States,''
and included intermittent streams, wetlands, sloughs, prairie potholes,
and wet meadows. This definition provided protection to nearly all
wetlands in the United States (Petrie et al. 2001, p. 1). However, two
Supreme Court rulings in 2001 and 2006 limited Federal authority under
the CWA to regulate certain isolated wetlands (Solid Waste Agency of
Northern Cook County v. U.S. Army Corps of Engineers, 531 U.S. 159,
(SWANCC) (2001) and Rapanos v. United States, 547 U.S. 715 (2006)).
Following the SWANCC and Rapanos decisions, it was unknown how the
Corps would interpret its jurisdictional lines (Petrie et al. 2001, p.
3). According to 2008 guidance documents of the Corps and Environmental
Protection Agency, the CWA applies to wetlands adjacent to navigable
waters of the United States. This means wetlands must have an unbroken
surface or shallow sub-surface connection to jurisdictional waters
(even if the connection is intermittent), be physically separated from
jurisdictional waters by manmade dikes or barriers or natural river
berms, or be in close proximity to navigable waters, supporting the
science-based inference that such wetlands have an ecological
interconnection with jurisdictional waters.
Currently, most Corps permit applications in central Nebraska are
for
[[Page 52669]]
restoration work along the Platte River by groups such as the PFW,
NGPC, and Ducks Unlimited (Moeschen 2011, pers. comm.). Typically, the
Service is made aware of these projects and has educated restoration
proponents on the Platte River caddisfly and its habitat so as to avoid
potential adverse impacts to extant populations. Also, sand and gravel
mining operations, if occurring within wetlands along the river, would
require a Corps permit. A Corps permit would provide the Service with
adequate opportunity to address concerns regarding fish and wildlife
resources, and any issued permit would require mitigation (offset
impacts, restore area of equal habitat value) at a minimum ratio of 1:1
(Corps 2005, p. 18). Furthermore, the Corps has been kept apprised of
all sites where the caddisfly occurs, and two Corps representatives
attended a workshop in 2010 that educated various agency personnel on
the Platte River caddisfly and its habitat.
Most sloughs that support a Platte River caddisfly population occur
in areas directly connected to or adjacent to the main channel of the
Platte, Loup, and Elkhorn Rivers. Adjacency under CWA is easily
determined for these sloughs. Four of the 35 sites occur in more off-
channel areas, and adjacency for these sloughs may not be as easily
determined. Despite occurring in more off-channel areas, these four
sloughs still likely receive protection from fill. For instance, two
sites on the Elkhorn River occur along roadsides, and FHWA and the
Nebraska Department of Roads notifies the Service when work within or
near wetland areas is scheduled to occur. If these areas become subject
to fill activities in the future, the Service would have an opportunity
to recommend ways to avoid and minimize impacts to the wetlands.
Meanwhile, Wild Rose Slough and the type locality on Crane Trust
property are protected from fill activities by way of a conservation
easement. Overall, 23 of 35 caddisfly populations occur within WMAs or
lands managed for conservation or roadsides and are protected from most
fill and development activities in wetlands (with the exception of
restoration work). Thus, the CWA adequately protects the Platte River
caddisfly and its habitat from fill and development activities now and
into the future, because: (1) The CWA would apply to the majority of
populations should such activities occur in the future; (2) 66 percent
of populations occur in protected areas; and (3) the Service and Corps
have engaged in proactive planning efforts so as to avoid impact to the
caddisfly and its habitat.
Several governmental and nongovernmental agencies are working to
secure water rights for environmental benefits and endangered and
threatened species in Nebraska; however, instream flow appropriations
do not ensure a stream will always contain water (Czaplewski 2009,
entire). Instream appropriations only ensure that the minimum flow
needs of species will be met before any future water development
projects can occur (Czaplewski 2009, entire). Therefore, in times of
drought and low flows, pre-existing water rights will be met before the
minimum flow needs of fish and wildlife species are met. However, we
previously determined that the Platte River caddisfly can withstand
drought to a certain degree even when coupled with existing water
development projects.
The Central Platte Natural Resources District (CPNRD) and NGPC each
have protected instream flow rights along the Platte River; however,
these are not enough to cover ``target flows'' outlined by the PRRIP
(NGPC 2008, p. 7). The PRRIP is working to address shortages to target
flows by managing an environmental account from reservoirs along the
Platte River in Nebraska and leasing water rights from willing
landowners. The PRRIP also has a goal of offsetting new depletions to
the system that occurred after July 1997 and restoring flows to the
river by 130,000 to 150,000 acre-feet per year between 2007 and 2019.
Efforts to augment current Platte River flows should provide adequate
protection for the Platte River caddisfly populations along the Platte
River, possibly with the exception of the type locality and Wild Rose
Slough. For instance, as discussed under Factor A, even with more water
in the river channel, the type locality and Wild Rose Slough may not
become inundated or remain inundated long enough to meet the needs of
the Platte River caddisfly (Harner and Whited 2011, entire).
Furthermore, the PRRIP seeks to augment sediment inputs to the central
Platte River, which should also help prevent future channel degradation
from impacting sloughs where the caddisfly occurs.
Passed in 2004, Nebraska State law LB 962 requires the Nebraska
Department of Natural Resources to work with each of the 23 Nebraska
Natural Resource Districts (NRDs) to address surface water and
groundwater appropriations in fully or over-appropriated basins. Basins
designated as fully appropriated are required to place a moratorium on
any new groundwater wells until an integrated management plan to
address depletion issues can be developed (NGPC 2008, p. 18). The law
does not prevent new groundwater wells from being drilled outside fully
appropriated basins, such as some areas on the Loup River. Future
groundwater well construction could contribute to some future loss in
slough habitat on the Loup and Elkhorn Rivers as has been observed on
the Platte, leading to future caddisfly habitat loss. However, we
estimate that the amount of habitat that could be impacted is small,
because new development is done on a limited basis, and each NRD
monitors groundwater and stream levels annually to ensure water
resources are not being depleted.
Summary of Factor D
Given that 66 percent of Platte River caddisfly populations occur
on protected lands, and current laws and regulations provide adequate
protection for slough habitat on private lands should future activities
occur within slough habitat, we conclude that the inadequacy of
existing regulatory mechanisms does not pose a threat to the Platte
River caddisfly.
Factor E. Other Natural or Manmade Factors Affecting Its Continued
Existence
Small Population Size
Small insect populations may be vulnerable to extirpation as a
result of random genetic drift, naturally occurring stochastic events,
or demographic stochasticity (Pimm et al. 1988, p. 757; Boyce 1992, p.
482; Purvis et al. 2000, p. 1949; Melbourne and Hastings 2008, p. 3).
Extinction of small populations is also likely to happen more quickly
than extinction of larger populations due to inbreeding (Brook et al.
2002, pp. 3-4), and this could affect the Platte River caddisfly in the
future.
We do not know the true population size of any of the known Platte
River caddisfly populations, but we do have information on the numbers
of individuals at 18 sites with the caddisfly. We previously discussed
that some sites support relatively low densities of the Platte River
caddisfly, but determined that finding low numbers of individuals at a
site is typical of the Ironoquia genus. We also determined that varying
population levels across the range of the Platte River caddisfly likely
represent the norm for the species, and varying population densities
are likely a product of the species occurring in more than one type of
habitat. Also, because of various life history traits that enable the
[[Page 52670]]
caddisfly to survive in temporary habitats, the caddisfly is more able
to withstand stochastic events than species less tolerant of extreme
weather events. Therefore, we have determined that small population
size does not pose a threat to the caddisfly.
Limited Dispersal Ability
The adult stage likely represents the most probable means of
dispersal (Williams 1996, p. 644; Petersen et al. 2004, p. 934) for the
Platte River caddisfly. Poor adult flight capabilities and a short
window of adult activity indicate that Platte River caddisfly dispersal
to new habitats and between populations is likely a rare event.
Observations when adults are active have found individuals underneath
vegetation and on or near the ground, particularly when it is windy,
and above vegetation or immediately adjacent to standing water in
slough habitat during more favorable weather conditions (Vivian 2009,
pers. obs.; Vivian 2010, pers. obs.; Geluso et al. 2011, p. 1024). When
active, the caddisfly has only once been observed to fly more than 10
meters, and wind seemed to greatly influence that individual (Vivian
2009, pers. obs.; Vivian 2010, pers. obs.). Platte River caddisfly
adults are also active for a short period of time (i.e., about 2 to 3
weeks) (Whiles et al. 1999, p. 539; Goldowitz 2004, p. 6), and this
likely limits the species' dispersal ability compared to other
caddisflies with longer adult lifespans (Svensson 1972; entire) and
could reduce the amount of genetic variability within populations.
Genetics techniques can be used to assess a species' dispersal
ability in the absence of direct observations of significant dispersal
events (Kelly et al. 2002, p. 1642). Amplified Fragment Length
Polymorphism has been used to determine the amount of genetic
similarity among five caddisfly populations from the Platte, Loup, and
Elkhorn Rivers (Cavallaro et al. 2011, entire). It was found that one
Platte River caddisfly population from near Sutherland, Nebraska, and
one near Kearney, Nebraska, had more genetic similarity to each other
than the population near Kearney did to a population near Gibbon,
Nebraska, despite the closer proximity of Kearney and Gibbon. Also, the
population near Gibbon was found to be more closely related to the
population near Loup City, Nebraska, even though Loup City is farther
from Gibbon than Kearney (~21 km or 13.1 mi) (Bunn and Hughes 1997, p.
341; Cavallaro et al. 2011, pp. 12, 15). The Elkhorn River population
tested was found to be the most dissimilar from all other populations
(Cavallaro et al. 2011, p. 7), but this may be more a product of
geographic isolation as opposed to habitat fragmentation. It was also
established that there is a low amount of gene flow among existing
Platte River caddisfly populations and more intra-population variation
than inter-population variation (Cavallaro et al. 2011, pp. 6-7).
The amount of genetic variability observed in the Platte River
caddisfly (Cavallaro et al. 2011, p. 7) is similar to what has been
observed in the caddisfly Wormaldia tagananana, which is identified as
having a limited range and presumed limited dispersal ability (Kelly et
al. 2002, p. 1646). Low gene flow between Platte River caddisfly
populations further corroborates that the caddisfly has a limited
ability to disperse to new habitats (e.g., restored sloughs, sites that
were previously extirpated), and that successful dispersal to new
habitats likely depends upon just a few individuals (Schmidt et al.
1995, p. 154; Cavallaro et al. 2011, pp. 6-7).
Although it has been identified that the Platte River caddisfly is
a poor disperser, this is a natural life-history trait. This behavior
would be detrimental to the species if the existing populations
remained isolated from one another. However, we have not identified
that habitat loss is presently occurring to the extent that the
fragmentation of Platte River caddisfly populations poses a threat to
the species. While sloughs on the different river systems and on both
sides of the 155-km (93-mi) distribution gap between Hershey and Elm
Creek, Nebraska, are isolated from one another, there is evidence of
gamete (male and female reproductive cells) exchange across river
systems given the similarity between the sites near Gibbon and Loup
City and between Kearney and Sutherland. Furthermore, there have been
live individuals or cases found at two restored sites. These
observations indicate that there is a limited amount of dispersal
occurring within relatively short time periods across short distances.
Summary of Factor E
In summary, although small population size and limited dispersal
ability have the potential to adversely impact the Platte River
caddisfly, there is no evidence that this is occurring or is likely to
occur in the near future. For instance, there are no known caddisfly
population extirpations that have occurred as a result of small
population size. We previously established that the Platte River
caddisfly has the ability to recolonize sloughs following stochastic
events and is well adapted to the environmental extremes found in the
Great Plains. Therefore, we conclude that other natural or manmade
factors do not pose a threat to the species.
Cumulative Impacts
Some of the threats discussed in this finding can work in concert
with one another to cumulatively create situations that will impact the
Platte River caddisfly beyond the scope of each individual threat. For
example, as mentioned under Factor A, the impacts of water development
on Platte River caddisfly habitat could be exacerbated by the effects
of drought and the projected increases in drought resulting from
climate change. In the absence of water development projects across the
landscape, the Platte River caddisfly is naturally tolerant of drought
because of its semi-terrestrial lifecycle and ability to recolonize
sloughs once they become inundated again following extended dry
periods. However, in the presence of water development, projects that
remove water from the Platte, Loup, and Elkhorn Rivers have the
potential to reduce the amount of available habitat across the
landscape to the point that, during drought, enough refugia may not be
available to sustain existing populations. Also, because of climate
change, the frequency of droughts is expected to increase, and this
will likely be exacerbated by ongoing water development. Water
development has the ability to exacerbate the effects of drought
(climate change-related or otherwise), because less water is flowing
through the system than what there would be in the absence of water
development. Future, extreme droughts and climate change are also
expected to facilitate the spread of non-native vegetation, and this
could result in a loss in habitat due to the encroachment of exotic
vegetation in sloughs. Because of these relationships, we will analyze
the cumulative impact of drought (as a result of climate change), water
development (human-caused water reduction), and invasive species.
Water Development, Drought, and Invasive Species
As mentioned previously, under normal conditions and otherwise, the
Platte River caddisfly has the ability to withstand drought, because it
enters into a dormant phase during the typical summer dry period.
However, extreme drought can adversely impact the caddisfly to the
point that it results in localized extirpations. For instance, extreme
drought resulted in the extirpation of the type locality and one
[[Page 52671]]
site near Shelton, Nebraska, in the early 2000s. The species has since
recolonized the type locality. The Shelton site has not been surveyed
since 2009, but it is possible the Platte River caddisfly has
recolonized this area. This indicates that there was likely sufficient
habitat available near the type locality during the drought to serve as
refugia for the caddisfly, and that within a short period of time
following disturbance, the species founded new populations in
previously occupied habitat.
The drought in the early 2000s occurred during a time when water
development projects, such as dams and diversions, were prevalent
across the landscape, particularly along the Platte River. The Platte
River is considered to be the most degraded portion of the range of the
caddisfly, but no new, large water projects have been implemented since
1956. Under current laws and regulations, we anticipate that current
conditions with respect to water development are not anticipated to
deteriorate along the Platte River or appreciably diminish on the Loup
and Elkhorn Rivers.
The caddisfly has already been shown to withstand the combined
effects of extreme drought and water-related impacts to its habitat.
The species is also still present following the proliferation of
invasive species along the Platte River during the drought in the early
2000s. Meanwhile, there are no new, large-scale water development
projects planned within the range of the caddisfly. Therefore, the
amount of habitat available to the caddisfly is not anticipated to
greatly diminish because of water development now or into the future.
While future, extreme droughts could result in extirpations of the
caddisfly at a local scale, from examining satellite imagery to
identify slough habitat, we find there is sufficient habitat available
surrounding current populations to serve as refugia for the species
during drought. Thus, there is no information to suggest that future,
extreme droughts resulting from climate change and current water
development projects will reduce the ability of existing caddisfly
populations to sustain themselves under a warmer and drier climate.
We previously identified that at three Platte River caddisfly sites
along the Platte River, Phalaris arundinacea (reed canarygrass) may
encroach enough in the future to contribute to the extirpation of the
caddisfly at these locations. There is no evidence that suggests
Phalaris arundinacea is resulting in habitat loss at the remaining 32
sites where the species occurs. Because of the current small number of
sites affected by invasive species (3 of 35), and our inability to
predict the future effects of invasive species on other caddisfly
sites, we do not find that invasive species pose a threat to the
species now or in the future.
Finding
As required by the Act, we considered the five factors in assessing
whether the Platte River caddisfly is endangered or threatened
throughout all of its range. We examined the best scientific and
commercial information available regarding the past, present, and
future threats faced by the Platte River caddisfly. We reviewed the
petition, information available in our files, other available published
and unpublished information, and we consulted with recognized
caddisfly, slough, and hydrology experts and other Federal, State, and
nongovernmental entities. On the basis of the best scientific and
commercial information available, we find that the Platte River
caddisfly is not in danger of extinction (endangered species) now or
likely to become an endangered species within the foreseeable future
(threatened species), throughout all or a significant portion of its
range. Therefore, we find that listing the Platte River caddisfly as an
endangered or threatened species is not warranted throughout its range
at this time.
The Platte River caddisfly is currently known from 35 locations
across three river systems, and the number of populations would most
likely increase with additional survey efforts, because potentially
suitable habitat has been identified but has not been surveyed.
Meanwhile, with the exception of the type locality, there is a lack of
information on population trends. It appears that the caddisfly
naturally occurs at varying densities depending on habitat type and may
even be classified as a habitat generalist. Because the species occurs
in more than one habitat type on three different river systems, the
caddisfly is well-represented across the landscape and is resilient to
the various stressors present throughout its range.
In this finding, we identified a number of potential stressors
under Factor A. The stressor most likely to constitute a threat to the
Platte River caddisfly and its habitat in the future is landscape-level
changes in hydrology. The Platte River is one of the most managed river
systems in the United States and contains several impoundments,
diversions, and groundwater withdrawals that have resulted in
hydrological and morphological changes to the floodplain. The
dewatering of the Platte River likely resulted in historical losses of
Platte River caddisfly habitat. Nonetheless, we have established that
most remaining populations are likely to remain adequately protected
across this portion of the species' range because of programs, such as
PRRIP and PFW, and the existence of protected areas where many Platte
River caddisfly populations occur. Although ongoing and future Platte
River channel degradation could potentially affect the Platte River
caddisfly and its habitat in the future, particularly at the Crane
Trust, restoration efforts are ongoing along the central Platte River
to stem this trend. These efforts should protect caddisfly populations
along the Platte River, where most stressors are concentrated, now and
into the future.
Climate change is a concern and is likely to render the range of
the Platte River caddisfly hotter and drier. Nonetheless, we have
determined that the species should withstand future climatic changes
because of various life-history traits that are common among semi-
terrestrial caddisflies and because of the distribution of its habitat
across the landscape. We have determined that the present or threatened
destruction, modification, or curtailment of its habitat or range
(Factor A) is not a threat to the Platte River caddisfly at this time.
We have determined that overutilization for commercial,
recreational, or scientific use (Factor B) is not a threat to the
species at this time. Neither disease nor predation (Factor C) is known
or expected to be a threat to the species. We have determined that the
inadequacy of existing regulatory mechanisms (Factor D) is not a threat
to the Platte River caddisfly, and that regulatory mechanisms currently
in place provide protection to the species. Regarding other natural or
manmade factors affecting its continued existence (Factor E), we do not
consider small population size or limited dispersal ability to
constitute a threat to the species. The available information does not
indicate that the caddisfly is being impacted genetically, or in any
other way, as a result of small population size or limited dispersal
ability, or that it will become an endangered or threatened species in
the foreseeable future due to stochastic events. We have also examined
the cumulative impact of various stressors acting together and whether
those pose a threat to the caddisfly. We have determined that, when
examined together, the cumulative impact of various stressors does not
pose a threat to the caddisfly.
[[Page 52672]]
Significant Portion of the Range
Having determined that the Platte River caddisfly is not an
endangered or threatened species throughout its range, we must next
consider whether there are any significant portions of its range where
the species is in danger of extinction or is likely to become an
endangered species in the foreseeable future. The Act defines
``endangered species'' as any species which is ``in danger of
extinction throughout all or a significant portion of its range,'' and
``threatened species'' as any species which is ``likely to become an
endangered species within the foreseeable future throughout all or a
significant portion of its range.'' The phrase ``significant portion of
its range'' (SPR) is not defined by the statute, and we have no
regulation governing SPR.
We interpret the phrase ``significant portion of its range'' in the
Act's definitions of ``endangered species'' and ``threatened species''
to provide an independent basis for listing; thus, there are two
situations (or factual bases) under which a species would qualify for
listing: A species may be an endangered or threatened species
throughout all of its range; or a species may be an endangered or
threatened species in only a significant portion of its range. If a
species is in danger of extinction throughout an SPR, the species is an
``endangered species.'' The same analysis applies to ``threatened
species.'' Based on this interpretation and supported by existing case
law, the consequence of finding that a species is an endangered or
threatened species in only a significant portion of its range is that
the entire species will be listed as an endangered or threatened
species, respectively, and the Act's protections will be applied across
the species' entire range. Because ``significant portion of its range''
provides an independent basis for listing and protecting the entire
species, we next turn to the meaning of ``significant'' to determine
the threshold for when such an independent basis for listing exists.
Although there are potentially many ways to determine whether a
portion of a species' range is ``significant,'' the significance of the
portion of the range should be determined based on its biological
contribution to the conservation of the species. For this reason, we
describe the threshold for ``significant'' in terms of an increase in
the risk of extinction for the species. We conclude that a biologically
based definition of ``significant'' best conforms to the purposes of
the Act, is consistent with judicial interpretations, and best ensures
species' conservation. Thus, as explained further below, a portion of
the range of a species is ``significant'' if its contribution to the
viability of the species is so important that without that portion, the
species would be in danger of extinction.
We evaluate biological significance based on the principles of
conservation biology using the concepts of redundancy, resiliency, and
representation. Resiliency describes the characteristics of a species
and its habitat that allow it to recover from periodic disturbance.
Redundancy (having multiple populations distributed across the
landscape) may be needed to provide a margin of safety for the species
to withstand catastrophic events. Representation (the range of
variation found in a species) ensures that the species' adaptive
capabilities are conserved. Redundancy, resiliency, and representation
are not independent of each other, and some characteristic of a species
or area may contribute to all three. For example, distribution across a
wide variety of habitat types is an indicator of representation, but it
may also may indicate a broad geographic distribution contributing to
redundancy (decreasing the chance that any one event affects the entire
species), and the likelihood that some habitat types are less
susceptible to certain threats, contributing to resiliency (the ability
of the species to recover from disturbance). None of these concepts is
intended to be mutually exclusive, and a portion of a species' range
may be determined to be ``significant'' due to its contributions under
any one or more of these concepts.
We determine if a portion's biological contribution is so important
that the portion qualifies as ``significant'' by asking whether without
that portion, the representation, redundancy, or resiliency of the
species would be so impaired that the species would have an increased
vulnerability to threats to the point that the overall species would be
in danger of extinction (i.e., would be ``an endangered species'').
Conversely, we would not consider the portion of the range at issue to
be ``significant'' if there is sufficient resiliency, redundancy, and
representation elsewhere in the species' range that the species would
not be in danger of extinction throughout its range if the population
in that portion of the range in question became extirpated (extinct
locally).
We recognize that this definition of ``significant'' (a portion of
the range of a species is ``significant'' if its contribution to the
viability of the species is so important that without that portion, the
species would be in danger of extinction) establishes a threshold that
is relatively high. On the one hand, given that the consequences of
finding a species to be an endangered or threatened species in an SPR
would be listing the species throughout its entire range, it is
important to use a threshold for ``significant'' that is robust. It
would not be meaningful or appropriate to establish a very low
threshold whereby a portion of the range can be considered
``significant'' even if only a negligible increase in extinction risk
would result from its loss. Because nearly any portion of a species'
range can be said to contribute some increment to a species' viability,
use of such a low threshold would require us to impose restrictions and
expend conservation resources disproportionately to achieve
conservation benefits. This would result in the listing being
rangewide, even if only a portion of the range of minor conservation
importance to the species is imperiled. On the other hand, it would be
inappropriate to establish a threshold for ``significant'' that is too
high. This would be the case if the standard were, for example, that a
portion of the range can be considered ``significant'' only if threats
in that portion result in the entire species' being currently
endangered or threatened. Such a high bar would not give the SPR phrase
independent meaning, as the Ninth Circuit held in Defenders of Wildlife
v. Norton, 258 F.3d 1136 (9th Cir. 2001).
The definition of ``significant'' used in this finding carefully
balances these concerns. By setting a relatively high threshold, we
minimize the degree to which restrictions will be imposed or resources
expended that do not contribute substantially to species conservation.
But we have not set the threshold so high that the phrase ``in a
significant portion of its range'' loses independent meaning.
Specifically, we have not set the threshold as high as it was under the
interpretation presented by the Service in the Defenders litigation.
Under that interpretation, the portion of the range would have to be so
important that current imperilment there would mean that the species
would be currently imperiled everywhere. Under the definition of
``significant,'' the portion of the range need not rise to such an
exceptionally high level of biological significance. (We recognize that
if the species is imperiled in a portion that rises to that level of
biological significance, then we should conclude that the species is in
fact imperiled throughout all of its range, and that we would not need
to rely on the SPR language for such a listing.)
[[Page 52673]]
Rather, under this interpretation we ask whether the species would be
an endangered species everywhere without that portion, i.e., if that
portion were completely extirpated. In other words, the portion of the
range need not be so important that even the species being in danger of
extinction in that portion would be sufficient to cause the species in
the remainder of the range to be an endangered species; rather, the
complete extirpation (in a hypothetical future) of the species in that
portion would be required to cause the species in the remainder of the
range to be an endangered species.
The range of a species can theoretically be divided into portions
in an infinite number of ways. However, there is no purpose to
analyzing portions of the range that have no reasonable potential to be
significant or to analyzing portions of the range in which there is no
reasonable potential for the species to be an endangered or threatened
species. To identify only those portions that warrant further
consideration, we determine whether there is substantial information
indicating that: (1) The portions may be ``significant,'' and (2) the
species may be in danger of extinction there or likely to become so
within the foreseeable future. Depending on the biology of the species,
its range, and the threats it faces, it might be more efficient for us
to address the significance question first or the status question
first. Thus, if we determine that a portion of the range is not
``significant,'' we do not need to determine whether the species is an
endangered or threatened species there; if we determine that the
species is not endangered or threatened in a portion of its range, we
do not need to determine if that portion is ``significant.'' In
practice, a key part of the determination that a species is in danger
of extinction in a significant portion of its range is whether the
threats are geographically concentrated in some way. If the threats to
the species are essentially uniform throughout its range, no portion is
likely to warrant further consideration. Moreover, if any concentration
of threats to the species occurs only in portions of the species' range
that clearly would not meet the biologically based definition of
``significant,'' such portions will not warrant further consideration.
To determine whether the Platte River caddisfly could be considered
an endangered or threatened species in a ``significant portion of its
range'', we reviewed the best scientific information with respect to
the geographic concentration of threats and the significance of
portions of the range to the conservation of the species. We first
evaluated whether substantial information indicated (i) the threats are
so concentrated in any portion of the species' range that the species
may be currently in danger of extinction in that portion; and (ii) if
so, whether those portions may be significant to the conservation of
the species. Our rangewide review of the species concluded that the
Platte River caddisfly is not an endangered or threatened species. As
described above, to establish whether any areas may warrant further
consideration, we reviewed our analysis of the five listing factors to
determine whether any of the potential threats identified were so
concentrated among the 35 populations that some portion of the range of
the Platte River caddisfly may be in danger of extinction now or in the
foreseeable future.
We found that most potential threats evaluated in this rule were
concentrated on the Platte River, and we have determined that these
potential threats, including but not limited to: landscape level
changes in hydrology, invasive species, climate change, drought,
flooding, grazing, inadequacy of existing regulatory mechanisms, and
poor dispersal ability, are not resulting in current losses of slough
habitat or losses of any of the 28 populations of the Platte River
caddisfly along the Platte River, nor are they likely to do so in the
foreseeable future. In addition, we find that the Platte River portion
of the range of the caddisfly is not endangered or threatened because
of existing programs and entities that are striving to protect current
channel conditions. There is also no information to indicate that the
potential threats analyzed under the five factors are contributing to a
decline in the number of Platte River caddisfly populations or amount
of slough habitat available along the central Platte River. For
instance, we analyzed projected increases in the frequency of droughts
in central Nebraska and how this could impact the Platte River
caddisfly and its habitat. We also considered how the effects of
climate change may be compounded by current levels of water development
and have determined that these threats are not likely to pose a threat
to the Platte River caddisfly across its range. Therefore, based on our
review, the available information does not indicate that any of the
potential threats we evaluated in all the factors under the Act were so
concentrated in any portion of the species' range as to find that the
Platte River caddisfly may currently be in danger of extinction in that
portion of its range. Because we find that the Platte River caddisfly
is not an endangered species in any portion of its range now or in the
foreseeable future, we need not address the question of whether any
portion may be significant.
Conclusion
Our review of the information pertaining to the five factors does
not support the assertion that there are threats acting on the species
or its habitat that have rendered the Platte River caddisfly to be in
danger of extinction or likely to become so in the foreseeable future,
throughout all or a significant portion of its range. Therefore,
listing the Platte River caddisfly as an endangered or threatened
species under the Act is not warranted at this time.
We request that you submit any new information concerning the
status of, or threats to, the Platte River caddisfly to our Nebraska
Field Office (see ADDRESSES) whenever it becomes available. New
information will help us monitor the Platte River caddisfly and
encourage its conservation. If an emergency situation develops for the
Platte River caddisfly or any other species, we will act to provide
immediate protection.
References Cited
A complete list of references cited is available on the Internet at
http://www.regulations.gov and upon request from the Nebraska Field
Office (see ADDRESSES).
Authors
The primary authors of this notice are the staff members of the
Nebraska Field Office.
Authority
The authority for this action is section 4 of the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Dated: August 20, 2012.
Benjamin N. Tuggle,
Acting Director, U.S. Fish and Wildlife Service.
[FR Doc. 2012-21352 Filed 8-29-12; 8:45 am]
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