Wisdom, M.J., R.S. Holthausen, B.C. Wales, C.D. Hargis, V.A. Saab, D.C. Lee, W.J. Hann, T.D. Rich, M.M. Rowland, W.J. Murphy, and M.R. Eames. 2000. Source Habitats For Terrestrial Vertebrates Of Focus In The Interior Columbia Basin: Broad-Scale Trends And Management Implications. Volume 1 -- Overview. Gen. Tech. Rep. PNW-GTR-485. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. http://www.fs.fed.us/pnw/pubs/gtr485/gtr485v1.pdf
RELEVANT TO: |
ROADS/OFF-ROAD VEHICLES INVASIVE SPECIES VEGETATION AND WILDLIFE MONITORING/ADAPTIVE MANAGEMENT |
DESCRIPTION
This excerpt from an Interior Columbia River Basin Forest Service General Technical Report on terrestrial vertebrates and broad-scale trends and management implications reviews scientific literature on the impact roads have on terrestrial vertebrates. The excerpt cites literature documenting specific impacts on various species present on one or more of these Three Forests (see below). References cited can be located on the website location of the entire Volume.
MAJOR FINDINGS
- Various road-associated factors can negatively affect habitats and populations of terrestrial vertebrates . Thirteen (13) factors were identified from scientific literature as being harmful to terrestrial vertebrates [Note: underlined species are present on one or more of the Three Forests: Dixie, Fishlake, and/or Manti-La Sal]:
- Snag reduction (affects cavity-using birds and mammals such as white breasted nuthatch, brown creeper, and fringed myotis)
- Down log reduction (affects cavity-using birds and mammals such as American marten and northern flying squirrel)
- Habitat loss and fragmentation (e.g., increasing invasive species; impacting interior species)
- Negative edge effects (affects interior species or species vulnerable to road mortality such as northern goshawk, golden-crowned kinglet, and northern flying squirrel)
- Over-hunting (including recreational killing of ground squirrels, many of which are local endemics, Including the Uinta ground squirrel and white-tailed ground squirrel)
- Over-trapping (particularly of carnivorous mammals such as American marten and fisher)
- Poaching (particularly of large mammals such as pronghorn, raptors such as the ferruginous hawk, and squirrels)
- Collection (particularly of snakes such as the striped whipsnake and the longnose snake, and lizards such as the longnose leopard lizard)
- Harassment or disturbance (particularly affecting leks, nests, dens; for species such as blue grouse, Lewis' woodpecker, and long-legged myotis)
- Collisions (particularly affecting reptiles and amphibians such as the longnose leopard lizard; granivorous birds attracted to roadside grains; carnivorous mammals; and birds such as the loggerhead shrike and the pine siskin)
- Movement barrier (particularly affecting small mammals such as shrews, as well as pronghorn and the short-eared owl)
- Displacement or avoidance (especially bats such as the Townsend's big-eared bat; elk)
- Chronic, negative interactions with humans (particularly affecting wolves and grizzly bears as well as some birds including the western meadowlark)
- Toxic pollution (particularly affecting terrestrial vertebrates inhabiting near-road areas
- " Effects of road-associated factors can be direct, such as habitat loss and fragmentation (Miller and others 1996, Reed and others 1996) or indirect, such as population displacement or avoidance in areas near roads in relation to motorized traffic and associated human activities (Mader 1984). Indirect effects can be subtle, such as the negative effects of all-terrain vehicles (Busack and Bury 1974, Lukenbach 1978) that can and do travel over a myriad of off-road and on-road conditions, and whose movements are facilitated by road access." (p. 112)
- Based on the factors listed above, >70 percent of the 91 broad-scale species of focus were found to be negatively affected by one or more factors associated with roads.
- Negative factors associated with roads, and their specific effects on habitats and populations, are diverse and not always easily recognized, and differentially affect different species and categories of species.
- These effects have strong management implications for landscapes characterized by moderate to high densities of roads.
- Source habitats likely are underused by many species when such habitats exist in areas that contain moderate to high road density.
- Mitigating the negative effects stemming from road-associated factors on these species will be as challenging, or perhaps more challenging, than that of maintaining or restoring vegetation used as source habitats by these species.
QUESTIONS RAISED FOR THE THREE FORESTS
- Have the Forests systematically balanced how many and which of its roads are "needed" for access benefits with the myriad adverse ecological effects they cause?
- Which sensitive species on the Three Forests are most likely to experience what types of road-related impacts documented in this Technical Report?
RELEVANCE TO FOREST MANAGEMENT
- The proximity of sensitive terrestrial vertebrate species habitat and populations to roads and motorized recreation must be noted, and typical impacts assumed and acknowledged, in absence of data to the contrary.
- Given that many road impacts can negatively impact or even threaten the integrity of species at the population level, long-term health and survival of sensitive, declining, and poorly-surveyed species must be explicitly considered when permitting roads.
- Negative, potentially irreversible, impacts to terrestrial vertebrate species must be weighed with desires of the public and of the Forests when determining how many and which roads are necessary and desirable.