Climate Change and Biodiversity: Paradise Lost or Found?
Peter Wilf, Pennsylvania State University

Abstract:
This session explores the effects of climate change on biodiversity, including discoveries from deep time, impacts on living marine microbes, and efforts to understand historical and project future effects on marine fish populations. Beginning with deep time (> ca. 2 million years ago), we first consider constraints on comparisons to the present day. Whereas anthropogenic climate change is predicted to occur over 102 – 103 years, the most rapid climate changes detected in the past took place over spans of 104 – 106 years, occurred without the human footprint, and usually started from an unglaciated climate state much warmer than present. Nevertheless, deep-time data uniquely cover intervals far longer than all of human history, and many relevant examples are emerging from the rapidly improving geologic and fossil record. Past warming is generally associated with massive range shifts and increased biodiversity, but at the expense of incumbent species. This pattern is seen both in the ocean and on land during a brief global warming, apparently caused by a major pulse of CO2 released from Indian volcanoes, ca. 300,000 years prior to the end of the Cretaceous period. Instead of causing mass extinction as sometimes suggested (vs. asteroid impact in Mexico 300,000 years later), this warming was clearly beneficial to life overall. Fossilized insect-feeding on plants indicates a significant correlation through time of insect diversity and herbivory with temperature, indicating more robust and speciose terrestrial food webs in warmer climates. High-rainfall terrestrial environments supported large numbers of species as they do now, showing that rainfall distribution is as important as temperature to biodiversity. Perhaps most strikingly, warmer past climates supported extensive high-latitude forests for most of the past 300 million years. Thus, slow global warming (104 - 106 years) under a minimal human footprint would probably increase biodiversity and bring many other “paradisiacal” benefits, but this outcome is unlikely in the near future because of the rapid rate of current warming and significant human impacts on natural abundance and habitat integrity.

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