Long-Term Ecological Records and Their Relevance to Climate Change Predictions for a Warmer World

This review focuses on biotic responses during intervals of time in the fossil record when the magnitude and rate of climate change exceeded or were comparable with those predicted to occur in the next century (Solomon et al. 2007). These include biotic responses during: (a) the Paleo-Eocene Thermal Maximum and early Eocene Climatic Optimum, (b) the mid-Pliocene warm interval, (c) the Eemian, and (d) the most recent glacial-interglacial transition into the Holocene. We argue that although the mechanisms responsible for these past changes in climate were different (i.e., natural processes rather than anthropogenic), the rate and magnitude of climate change were often similar to those predicted for the next century and therefore highly relevant to understanding future biotic responses. In all intervals we examine the fossil evidence for the three most commonly predicted future biotic scenarios, namely, extirpation, migration (in the form of a permanent range shift), or adaptation. Focusing predominantly on the terrestrial plant fossil record, we find little evidence for extirpation during warmer intervals; rather, range shifts, community turnover, adaptation, and sometimes an increase in diversity are observed.