Len Ruggiero, Kevin McKelvey, John Squires, and William Block, Wildlife and Terrestrial Ecosystem Program, Rocky Mountain Research Station.
The current version of this paper (2013) is available at www.fs.usda.gov/ccrc/topics/wildlife/mammals
Climate change likely will lead to the loss of native species from extensive areas and result in increasingly scarce and fragmented populations in many others. Further changes within ecosystems will be triggered as invasive species, both plant and animal, fill the "holes" that are left as native species are lost. Associated changes in the food-web will cascade and further destabilize ecosystems.
Species such as the Canada lynx (Lynx canadensis), wolverine (Gulogulo), snowshoe hare (Lepus americanus), white-tailed ptarmigan (Lagopus leucurus), and short-tailed weasel (Mustela erminea) have adapted to snowy environments with pelage or plumage that turns white in the winter. The snowshoe hare is also well adapted to deep snow based on its large snowshoe-like feet. A warming climate will put this species at a disadvantage, and, importantly, this species is a food source for many predators. Specific tight relationships between predators and their prey (e.g., between lynx and hares, and between goshawks (Accipiter gentilis)/martens (Martes americana) and red squirrels (Tamiasciurus hudsonicus)) will break apart as the species respond differently to climate changes.
Rising temperatures may exceed the thermal tolerances of species such as bull trout (Salvelinus confluentus) and cutthroat trout (Oncorhynchus clarki). Also, species like the Mexican spotted owl (Strix occidentalis lucida) and the pike (Esox spp.) will likely be impacted as habitats contract with warming climates. Native species may be further stressed by the proliferation of invasive species that thrive in warmer conditions. For example, invasive brown trout (Salmo trutta) are favored by warmer temperatures and may outcompete native cutthroat trout.
Cold-adapted ecosystems such as boreal forests and alpine meadows will become smaller and eventually lost as they are pushed up the mountains. Populations of fauna associated with these ecosystems will become increasingly fragmented and prone to extinction. The issues currently associated with the "sky islands" in the Great Basin and Madrean Archipelago, such as isolation and restricted species movement, will become prevalent throughout western montane areas. For example, populations of wolverines may become isolated on lingering high-elevation, boreal "islands," threatening the long-term viability of the species.
Increases in disturbance owing to fire, insects, and disease will accelerate the infiltration of weeds. The loss of native ecosystems to weeds affects many species as the effects of changing plant communities ripple through the ecosystems. Many animal species likely will be lost as vegetation patterns change (e.g., endangered Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis) on the "sky islands").
Some of the potentially affected species are currently listed by the U.S. Fish and Wildlife Service as threatened or endangered. Others, such as the wolverine, which has been petitioned for listing, may become in danger of extirpation or even extinction. Working to maintain the survival of these species requires informed management.
What are the likely specific ecological effects of climate change on wildlife and fish?
Answering this question requires detailed information on the biology of affected organisms, their habitat relations, and determining their bioclimatic tolerances. This information will allow efficient application of scarce resources associated with mitigation.
How do topography and vegetative land cover types affect wildlife dispersal?
Planning for dispersal will be increasingly important because it can limit the need for expensive mitigation such as population augmentation or reintroductions.