The view of climate change during the Pleistocene and the Holocene was very much different a mere decade ago. With the collection and detailed analyses of ice core records from both Greenland and Antarctica in the early and mid-1990s, respectively, the collective view of climate variability during this time period has changed dramatically. During the Pleistocene, at least as far back as 450,000 years b.p., abrupt and severe temperature fluctuations were a regular occurrence rather than the exception (Mayewski et al. 1996, 1998; Petit et al. 1999). During the Pleistocene, these rapid and large climatic fluctuations, initially identified in the ice core records, have been verified in both marine and lacustrine sediments as well (Bond et al. 1993; Grimm et al. 1993), suggesting large-scale (hemispheric to global) climate restructuring over very short periods of time (Mayewski et al. 1997). Similar types of climatic fluctuations, but with smaller amplitudes, have also occurred during the Holocene (O’Brien et al. 1995; Bond et al. 1997; Arz et al. 2001). What were the biological responses to these changes in temperature, precipitation, and atmospheric chemistry? We must answer this question if we are to understand the century- to millennial-scale influence of climate on the structure and function of ecosystems. Because the polar regions are thought to be amplifiers of global climate change, these regions are ideal for investigating the response of ecological systems to, what in temperate regions might be considered, small-scale climatic variation. Our knowledge of past climatic variations in Antarctica comes from different types of proxy records, including ice core, geologic, and marine (Lyons et al. 1997). It is clear, however, that coastal Antarctica may respond to oceanic, atmospheric, and ice sheet–based climatic “drivers,” and therefore ice-free regions, such as the Mc- Murdo Dry Valleys, may respond to climate change in a much more complex manner than previously thought (R. Poreda, unpubl. data 2001). Since the initiation of the McMurdo Dry Valleys Long-Term Ecological Research program (MCM) in 1993, there has been a keen interest not only in the dynamics of the present day ecosystem, but also in the legacies produced via past climatic variation on the ecosystem. In this chapter we examine the current structure and function of the dry valleys ecosystem from the perspective of our work centered in Taylor Valley.
Isotopic paleoecology of Northern Great Plains bison during the Holocene