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Plant Avoidance and Minimization Measures

The following measures are recommended to avoid or minimize project impacts to threatened and endangered plants in the Hawai'i and the Pacific Islands. 

  • Avoidance, Minimization, and Conservation Measures for Threatened and Endangered Plant Species in Hawaii.

    (June 2018)

    In the Pacific Islands, a total of 442 plant species are Federally-listed as endangered or threatened; these include 425 species in the Hawaiian Islands (416 endangered and 9 threatened) and 17 species in Guam and the Northern Mariana Islands (10 endangered and 7 threatened). 

    Currently, there are no Federally-listed plant species in American Samoa. Listed plants occur across all native ecosystem types and in a broad range of plant communities including disturbed areas and those degraded by nonnative plant species.  Listed plants are represented by various growth forms including trees, shrubs, herbs, vines, grasses, and ferns.

    The Federally-listed plant species in the Hawaiian Islands face numerous threats, including habitat destruction and modification by agriculture and development, nonnative ungulates, nonnative plants, fire, hurricanes, drought, disease and pathogens; herbivory by nonnative invertebrates, introduced small mammals and ungulates; and other factors such as small population size, reduced genetic variation, hybridization, the effects of climate change, and other stochastic factors (USFWS 2010, 2012, 2013a, 2013b, 2016).  Currently, less than half of the Federally-listed plant species in Hawaii exhibit stable or increasing trends (USFWS 2016, unpublished). 

    Project activities may affect listed plant species by causing physical damage to plant parts (roots, stems, flowers, fruits, seeds, etc.) as well as impacts to other life requisite features of their habitat which may result in reduction of germination, growth and/or reproduction.  Cutting and removal of vegetation surrounding listed plants has the potential to alter microsite conditions (e.g., light, moisture, temperature), increase the risk of invasion by nonnative plants which can result in higher incidence or intensity of fire.  Activities such as grazing, use of construction equipment, vehicles, and increased human traffic (i.e. trails, visitation, monitoring), can cause ground disturbance, erosion, and/or soil compaction which decrease absorption of water and nutrients and damage plant root systems and may result in reduced growth and/or mortality of listed plants.  Soil disturbance or removal has the potential to negatively impact the soil seed bank of listed plant species if such species are present or historically occurred in the project area.

    Minimize potential adverse effects to listed plants that may occur on the proposed project site by minimizing disturbance outside of existing developed or otherwise modified areas. When disturbance outside existing developed or modified sites is proposed, conduct a botanical survey for listed plant species within the project action area, defined as the area where direct and indirect effects are likely to occur.  Surveys should be conducted by a knowledgeable botanist with documented experience in identifying native Hawaiian plants, including listed plant species.  Botanical surveys should optimally be conducted during the wettest part of the year (typically October to April) when identifiable features of the plants (fruit, flowers, etc.) are more likely to be visible, especially in drier areas.  If surveys are conducted outside of the wet season, the Service may assume plant presence.

    The boundary of the area occupied by listed plants should be marked with flagging by the surveyor.  To avoid potential adverse effects to listed plants, we recommend adherence to buffer distances for the activities in the Table below. Where disturbed areas do not need to be maintained as an open area, restore disturbed areas using native plants as appropriate for the location.

    If listed plants occur in a project area, the avoidance buffers are recommended to reduce direct and indirect impacts to listed plants from project activities.  However, where project activities will occur within the recommended buffer distances, additional consultation is required.  The impacts to the plants of concern within the buffer area may be reduced by placing temporary fencing or other barriers at the boundary of the disturbance, as far from the affected plants as practicable.

    All activities, including site surveys, risk introduction of nonnative species into project areas.  Specific attention needs to be made to ensure that all equipment, personnel and supplies are properly checked and are free of contamination (weed seeds, organic matter, or other contaminants) before entering project areas.  Quarantines and or management activities occurring on specific priority invasive species proximal to project areas need to be considered or adequately addressed.  This information can be acquired by contacting local experts such as those on local invasive species committees (Kauai:; Oahu:; Maui Nui:; and Hawaii:

    The above guidelines apply to areas outside of designated critical habitat.  If project activities occur within designated critical habitat unit boundaries, additional consultation is required.



    Recommended buffer distances for no effect determination. (N/A = additional consultation is required).

    *Use of Approved Herbicides (following label)
    **Surface Hardening/Soil compaction
    ***Buffer Distance (feet) – Keep Project Activity This Far Away from Listed Plant




    Cutting and Removing Vegetation By Hand or Hand Tools (e.g., weeding)

    3 ft (1 m)

    3 ft (1 m)

    Mechanical Removal of Individual Plants or Woody Vegetation (e.g., chainsaw, weedeater)

    3 ft up to height of removed vegetation (whichever greater)

    3 ft up to height of removed vegetation (whichever greater)

    Removal of Vegetation with Heavy Equipment (e.g., bulldozer, tractor, "bush hog")

    2X width equipment + height of vegetation

    820 ft (250 m)

    *Hand Application (spot treatment)

    10 ft (3 m)

    Crown diameter

    *Ground-based Spray Application (e.g. backpack, tank sprayer)

    50 ft (15 m)

    250 ft (76 m)

    *Aerial spray (ball applicator)

    250 ft (76 m)

    250 ft (76 m)

    *Aerial spray (paintball)(individual plant treatment)

    100 ft (30 m)

    100 ft (30 m)

    *Aerial spray (boom)



    Ground/Soil Disturbance/Outplanting/Fencing (Hand tools, e.g. shovel, or Small mechanized tools, e.g., auger)

    20 ft (3 m)

    2x crown diameter

    Ground/Soil Disturbance (Heavy Equipment)

    328 ft (100 m)

    820 ft (250 m)

    **Trails (e.g., human, ungulates)

    20 ft

    2x crown diameter

    **Roads/Utility Corridors, Buildings/Structures

    328 ft (100 m)

    820 ft (250 m)

    Prescribed Burn/Fires




    820 ft (250 m)

    820 ft (250 m)



    Definitions (Wagner et al. 1999)

    Crown: The leafy top of a tree.

    Herb: A plant, either annual, biennial, or perennial, with the non-woody stems dying back to the ground at the end of the growing season.

    Shrub: A perennial woody plant with usually several to numerous primary stems arising from or relatively near the ground.

    Tree: A woody perennial that usually has a single trunk

    References Cited

    USFWS. 2010. Endangered and threatened wildlife and plants; determination of endangered status for 48 species on Kauai and designation of critical habitat. Federal Register 75: 18960-19165.

    . 2012. Endangered and threatened wildlife and plants; endangered status for 23 species on Oahu and designation of critical habitat for 124 species; final rule.   Federal Register 77: 57648-57862.

    . 2013a Endangered and threatened wildlife and plants; determination of endangered status for 38 species from Molokai, Lanai, and Maui.  Federal Register 78: 32014-32065.

    . 2013b. Endangered and threatened wildlife and plants; determination of endangered species status for 15 species on Hawaii Island. Federal Register 78: 64638-64690.

    . 2016. Endangered and threatened wildlife and plants; determination of endangered status for 49 species from the Hawaiian Islands. Federal Register 81: 67786-67860.

    . 2016. USFWS Rare plant database. Unpublished.

    Wagner, W.L., Sohmer, S., and D.R. Herbst. 1999. Manual of the flowering plants of Hawaii, revised edition. Honolulu, Hawaii. University of Hawaii and Bishop Museum Press.

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