Climate change and Arctic ecological responses – past, present and future

Glen M. MacDonald

University of California, Los Angeles, USA

Since the mid-20^th century, large areas of the high-latitudes of the northern hemisphere have been warming at a rate greater than almost any other part of the earth. The rate and geographic concentration of warming in the Arctic and adjacent Subarctic are consistent with the impact of projected global warming patterns caused by increasing greenhouse gases. If greenhouse gasses were to stabilize at current levels, which is highly improbable, this warming would continue beyond the end of the century. Current projections of future warming based upon a variety of assumptions regarding greenhouse gas generation suggest that annual temperatures in the Arctic/Subarctic will increase by as much as 7°C by 2100. Not only will the climate change, but there will be radical alterations in habitat that could present serious challenges to Arctic animal species. Retrospective analyses of natural climate variability in the Arctic during the last 11,000 to 1 million years suggest that the 21^st century warming will be unprecedented in terms of geographic patterns and magnitude. In addition, the seasonal distribution of warming will differ strongly from past natural events. At present, the potential effects of these climate changes on species distributions are most often tackled using a framework derived essentially from Grinnellian niche theory, which combines empirical data on current geographic distributions of species and contemporary climatic values. It will be illustrated why this approach is insufficient and why a concerted effort to study the population ecology and physiology of Arctic and Subarctic species is of critical importance today.