People in many parts of the world are dependent on wildlife for all or part of their daily nutritional needs. A typical adaptive response to this situation would be to replace all or part of this food with store-bought products. This might be feasible in areas near developed societies but could become increasingly difficult in more remote communities. However, there is more to subsistence hunting than the capture of food. Subsistence hunting plays a major role in the culture of Cree communities in northern Canada. "The killing, preparation, sharing, and consumption of game is central to the seasonal renewal of social relations in Cree villages, and of a relationship to the land which is both secular and sacred in importance" (Scott, 1987). Even if compensations or substitutions for subsistence uses could be made, there still would be equity issues stemming from the loss of culture associated with this way of life.

Many of the aforementioned potential adaptations are more applicable to developed countries than in developing countries. For example, the use of leased honeybees is not applicable to crops fertilized by flying foxes or other wild animals. The same can be said of many forms of seed dispersal. Increased use of pesticides may require more capital than is available to small farmers in some developing countries (Pimentel et al., 1992). Adaptations that may be practical for developed countries simply may not be equitable for developing countries.

In trying to understand and predict potential impacts of climate change on wildlife species, some species and geographic areas are found to be at greater risk than others. Species with small populations, restricted ranges, and specific habitat requirements often are most vulnerable (see Section 5.4.1.2).

Migratory species may be especially vulnerable because they require separate breeding, wintering, and migration habitats. In many cases, one or more of these habitats could be at risk because of climate change and other habitat loss. For example, a large portion of the eastern population of the monarch butterfly (Danaus plexippus) winters in a small region of warm-temperate dry forest in Mexico. With climate change, this area is projected to contain trees that are more typical of a subtropical dry forest—probably unsuitable for wintering monarchs (Villers-Ruíz and Trejo-Vázquez, 1998). The relative vulnerability of shorebird migration sites in the United States varies, depending on local geomorphologic and anthropogenic factors, and these factors could exacerbate the effects of sea-level rise. For example, southern San Francisco Bay could lose most of its intertidal feeding habitat with a 2°C average temperature rise (medium confidence) (Galbraith et al., 2001).

One key region of concern is the Arctic and Antarctic, where the temperature increase is projected to be large and changes to habitat availability and accessibility (e.g., freezing and thawing of sea ice and tundra) are expected. Such changes may hamper migration, reproduction, and survival of many species, including birds, polar bears (Ursus maritimus), caribou, and musk-oxen (Jefferies et al., 1992; Stirling and Derocher, 1993; Gunn and Skogland, 1997; Stirling, 1997).

Many biological uncertainties exist in the understanding of ecosystem processes. Nevertheless, the balance of evidence suggests that projecting impacts of climatic change on a variety of wildlife species is possible (medium confidence). Laboratory and field studies have demonstrated that climate plays a strong role in limiting species' ranges (high confidence). Only a small fraction of all species have been monitored long enough to detect significant trends. Most monitored species that show significant trends have exhibited changes over the past few decades that are consistent with local warming and expected physiological responses (high confidence). However, potential specific changes in wildlife resulting from climate change can be projected only with low confidence for most species because of many possible contributing factors, such as habitat destruction and exotic invasive species. Some species clearly are responding to global change (see Section 5.4.3), and many more changes probably have gone undetected. Researchers are in the process of coupling these discernible changes with various biological theories regarding climate and species spatial and temporal patterns; through this process, we expect that reliable general projections can be and in fact are being made (high confidence).

Scientists also need to develop a better understanding of how all of the components of ecosystems work together. The role each species plays in ecosystem services, in wild and managed systems, is necessary to understand risks and possible surprises associated with species loss. Without this information, the probability of surprises associated with species loss is high (medium confidence).

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