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Arctic Science 2000 - Crossing Borders: Science and Community
Whitehorse, Yukon, Canada, Sept 21-24 2000
American Association for the Advancement of Science & Yukon Science Institute

Are Mammals Useful Indicators of Climate Change? Evidence from the Southwest Yukon

What species are good indictors of climate change? Are some taxa less or more sensitive to climatic variability and change? Several studies have suggested that some populations of both large and small mammals will be significantly affected by climate change, but there are still few studies where we understand the relationship between climate and demography, growth or survival of northern mammals. This presentation will summarize and interpret our understanding of climate impacts on mammals in the southwest Yukon.

Climate change impacts are expected to be exaggerated in these sub-arctic mountainous areas by a combination of rugged topography, low sun angle, strong seasonal differences in radiation, and extreme ecological zonation with altitude. Climate data has been collected since 1967 at two valley-bottom stations, however there is little data from above tree-line. A 350-year record of annual precipitation and temperatures is also available from the Mt. Logan ice-core. More importantly, population records for many mammalian species extend over 25 years in this region, providing a suitable baseline for attempting to interpret sensitivity to climate.

Alpine species appear to be more sensitive indicators of climatic variability than boreal forest species, likely because there are fewer predators in the alpine and the snow-free growing season is relatively shorter. Herbivores also appear to be more sensitive to climatic variability than predators. In the boreal forest, small mammal populations are generally driven by snowshoe hare population dynamics, although there are a few exceptions. Large herbivores (moose, caribou) also appear to be largely regulated by predation. Climate may mediate longer-term patterns, but most dynamics are internal and related to predation, such that trophic cascades generally overwhelm environmental effects. Less is known about alpine species, but many appear to be quite sensitive to climatic conditions. Long-lived species such as Dall’s sheep show variation in reproduction, recruitment and growth related to climate. Some small mammals such as collared pikas appear to be very sensitive to winter conditions, while others do not (e.g. hoary marmots), however these records only extend over 6 years so far. Overall, there is still insufficient information to determine what the impacts of climate change will be on mammals in the southwest Yukon.

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