Biological Impacts of Climate Change

Global climate is swiftly changing, with poorly known consequences for biodiversity and human well being. In the last 90 years Earth’s mean temperature rose 0.6°C, a rate of increase that has not been seen in 10,000 years. Since the mid-1990s, it has been clear that mean global temperature rose during the twentieth century, but for several more years the cause of the observed warming was much debated in scientific circles. The United Nations and the World Meteorological Organization perceived that if humans were causing a fundamental shift in global climate, the consequences could be enormous for all peoples. To facilitate reaching a global scientific consensus, the Intergovernmental Panel on Climate Change (IPCC) was formed, whose Third Assessment Report (IPCC 2001a) involved more than 1200 scientists from diverse disciplines. The consensus among the more than 200 climate experts from IPCC Working Group I was that “global rises in mean yearly temperature of the past 50 years were primarily due to global rises in anthropogenically produced greenhouse gases” (i.e., carbon dioxide, methane, nitrous oxide, and halocarbons) and that the rate of temperature change will itself accelerate over the coming century (IPCC 2001a). As with many other conservation issues, however, the most influential debates— those in the policy and public arenas—continue well beyond the point of scientific consensus. And, indeed, consensus on the cause of global warming is only the beginning of a series of new questions. What does anthropogenic climate change signify for the future? Is climate change a reversible process, and how quickly will new weather patterns emerge? What can be done to mitigate the detrimental effects of altered climates? How will new climatic patterns influence species and ecosystems already besieged by other human-induced pressures? Signs of climate change are already visible, although most effects have been relatively mild compared to other anthropogenic threats to wild species, particularly habitat loss and degradation. Conservation concerns about climate change are less focused on current impacts or even on impacts over the next decade but on consequences from 50 to 100 years from now. Existing climate models predict widespread © 2005 Sinauer Associates, Inc. This material cannot be copied, reproduced, manufactured, or disseminated in any form without express written permission from the publisher.