Impacts of Extreme Weather and Climate on Terrestrial Biota

Climate is a driver of biotic systems. It affects individual fitness, population dynamics, distribution and abundance of species, and ecosystem structure and function. Regional variation in climatic regimes creates selective pressures for the evolution of locally adapted physiologies, morphological adaptations (e.g., color patterns, surface textures, body shapes and sizes), and behavioral adaptations (e.g., foraging strategies and breeding systems). In the absence of humans, broad-scale, long-term consequences of climatic warming on wild organisms are generally predictable. Evidence from Pleistocene glaciations indicates that most species responded ecologically by shifting their ranges poleward and upward in elevation, rather than evolutionary through local adaptation (e.g., morphological changes). But these broad patterns tell us little about the relative importance of gradual climatic trends as compared to extreme weather events in shaping these processes. Here, evidence is brought forward that extreme weather events can be implicated as mechanistic drivers of broad ecological responses to climatic trends. They are, therefore, essential to include in predictive biological models, such as doubled CO 2 scenarios. *This is the fifth of five papers in the “Understanding Changes in Weather and Climate Extremes” series. National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara, Santa Barbara, California. School of Natural Resources and Environment, University of Michigan, Ann Arbor, Michigan. Program in Ecology and Conservation Biology, Department of Biological Sciences and the Museum, Texas Tech University, Lubbock, Texas. Current affiliation: Department of Integrative Biology, University of Texas at Austin, Austin, Texas. Corresponding author address: Dr. Camille Parmesan, Integrative Biology, University of Texas at Austin, Austin, TX 78712. E-mail: [email protected] In final form 6 October 1999. ©2000 American Meteorological Society