MAMMALIAN RESPONSES TO CLIMATE CHANGE: CONSERVATION LESSONS FROM DEEP-TIME EXPERIMENTS

Clarifying mammalian responses to climate change is necessary to predicting long-term responses and making informed management decisions. However, long-term experiments can be logistically challenging and limited in the amount of time they actually capture. Fossil and archeological records can instead provide "deep-time data" that can be used to test biological hypotheses of relevance today. For example, examining mammalian responses to interglacial warming and/or increased aridity during the Pleistocene can offer insights regarding how mammals may respond to current climate change. Here, I discuss global records of Pleistocene faunas ranging from the southeastern United States to New South Wales, Australia. Most notably, interglacial warming in Florida resulted in a more heterogeneous landscape and less dietary overlap (as inferred from carbon isotopes) than during glacial times. In contrast, increased aridity reduced the consumption of C₄ resources consumed in Australia. While floral responses to climatic changes in these two regions may be different, what is clear is that more heterogeneous landscapes support a greater variety of dietary niches and potentially higher taxonomic diversity. In addition, these long-term records can test ideas fundamental to current predictions of future species distributions. Specifically, bioclimatic envelope models assume that what a species does today a species will do tomorrow. Instead, these deep-time records demonstrate the absence of niche conservation at the generic level as dietary niches of many taxa do change quite dramatically. Collectively, deep-time experiments can provide insight regarding long-term mammalian responses to climate change and other questions of fundamental importance to conservation biology.