Pools Species Receives Critical Habitat Designation
The U.S. Fish and Wildlife Service has designated
approximately 740,000 acres in 30 California counties and one Oregon
county as critical habitat for 15 wetland animals and plants listed
as threatened or endangered under the Federal Endangered Species
The species included in the August 6, 2003 critical
habitat designation are four types of freshwater shrimp
the Conservancy fairy shrimp, longhorn fairy shrimp, vernal pool
tadpole shrimp and vernal pool fairy shrimp; and 11 plants that
depend on seasonally flooded wetlands known as vernal pools.
One species, the vernal pool fairy shrimp, is also found in Jackson
county in Oregon.
Typical Vernal Pool
Description. Vernal pools are seasonal wetlands that
form only in regions where specialized soil and climatic conditions
exist. During fall and winter rains typical of Mediterranean
climates, water collects in shallow depressions where downward
percolation of water is prevented by the presence of a hard
pan or clay pan layer (duripan) below the soil surface. Later
in the spring when rains decrease and the weather warms, the
water evaporates and the pools generally disappear by May.
The shallow depressions remain relatively dry until late fall
and early winter with the advent of greater precipitation and
Specific Adaptations. Vernal pools provide unusual
"flood and drought" habitat conditions to which certain
plants and animals have specifically adapted. Vernal pools are
a prominent feature of the Agate Desert landform, north of Medford,
where they are an important link in the food chain for migrating
waterfowl, shorebirds, birds of prey, frogs, toads, salamanders
and pollinating insects.
Diminishing Habitat. Only 23 percent of the original
vernal pool topography and hydrology in the Agate Desert remains
intact. Residential, commercial, and industrial development,
along with land leveling, have claimed nearly 60 percent of the
historic range of this Agate Desert landform. The remainder of
the habitat is either severely altered by historic and continuing
land uses, or occurs along the fringes of the landform where
vernal pools are weakly expressed.
release: USFWS Designates Critical Habitat for Threatened
and Endangered Vernal Pool Species (August 2003)