Climate plays an important role in determining the limits of species ranges. A species range is usually viewed as a north-to-south continuum with population densities slowly decreasing toward each end. However, variability in microclimate over a range of scales may cause breaks within this continuum, so that the abundance of organisms and levels ofphysiological stress wax and wane along each species distribution. Therefore, identifying the scale over which climate drives patterns of species distributions is the key to predicting the effects of climate change on ecological communities.
Climates are dynamic and warming and cooling trends occur both slowly, over the course of millennia, and more quickly over a period of years (e.g., El Nino Southern Oscillation and related La Nina events). Microclimates are ultimately derived from the overall climate of an area, so significant changes at the large-scale level will usually be reflected at the small-scale level. However, microclimates include multiple factors, and it can be difficult to predict the long-term direction of change. By observing the changes in particular microhabitats more vulnerable to climate change, it may be possible to make better predictions. For example, a community living on the south face of a mountain in the Northern Hemisphere may exhibit responses to climatic change earlier than a community on a nearby north face. Conditions observed in these vulnerable areas can be used in mathematical models to explore the possible changes in species distributions.
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