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63 Climate Change and Biodiversity in the Great Lakes Region From “Fingerprints” of Change to Helping Safeguard Species KIMBERLY R. HALL AND TERRY L. ROOT Over the last century, the average global surface temperature has increased approximately 0.8ºC, and the rate of warming continues to accelerate (Trenberth et al. 2007). Even with this amount of warming, which is small compared to the net increase we may see in the relatively near future (an additional 1.1º to 6.4ºC or more increase in the global average by 2100 according to Meehl et al. 2007), wild species are already exhibiting discernible changes (Root et al. 2003; Parmesan and Yohe 2003; Parmesan 2006). Like other regions at moderate latitudes, temperature change projections for the Great Lakes region are somewhat higher than projections for the global average. Temperatures in winter are rising faster than any other season, which may seem like a welcome change to some residents, but can lead to costly impacts in agricultural and managed forest systems through increases in the survival of crop and forest pests (CCSP 2009; Bradshaw et al., this volume). Specifically, winter temperatures will be “less cold” (nightly low temperatures are expected to increase more than the daytime highs), contributing to lengthening of the frost-free growing season, which has already increased by more than one week (Field et al. 2007; CCSP 2009; Andresen, this volume). By the end of this century, average summer temperatures are projected to increase by 3º to 7ºC, leading to dramatic increases in the frequency of heat waves, especially if the temperature increase is at 64| Kimberly R. Hall and Terry L. Root the higher end of this range (Christensen et al. 2007; CCSP 2009; Hayhoe et al. 2010b). Summer surface water temperatures in the upper Great Lakes (Michigan, Huron, Superior) are currently increasing even faster than the air temperatures, and these changes are triggering a whole range of systemwide impacts, including increases in wind and current speeds, and increases in the duration of the stratified period (Austin and Coleman 2007, 2008; Desai et al. 2009; Dobiesz and Lester 2009). The rate at which these temperature changes are occurring suggests that many, if not most, wild species will experience climate change as a stressor that reduces survival and/or reproduction, and thus has strong potential to lead to population declines, or even extinction. The most recent Intergovernmental Panel on Climate Change (IPCC) report, which represents the consensus view of a team of hundreds of scientists from across the globe, suggests that 15 to 40 percent of known species will be at an increasingly high risk of extinction as global mean temperatures reach 2º to 3ºC above pre-industrial (or 1.2 to 2.2ºC above current) levels (Field et al. 2007, based on work in Thomas et al. 2004). Identifying the most vulnerable species, and what we can do to safeguard their populations, is a major challenge, and each day that passes without reductions in the gases that trap heat in our atmosphere (carbon dioxide, methane) stacks the odds further against the survival of sensitive species and systems. Here we review observed and predicted impacts of climate change on biodiversity in the Great Lakes region, with the goal of helping to inform and motivate actions that reduce emissions, and to promote actions that help safeguard species and systems so that they can adapt to ongoing changes. Although the scientific literature documenting climate change impacts on species is rapidly expanding, predicting how and when focal species will respond is a daunting task, in part because changes in temperature and other factors are happening within a climate system that already exhibits high natural variation across both space and time. The observed changes, along with ecological theory, allow us to develop “rules of thumb” for how species are likely to respond to the most direct aspects of climate change (e.g., changes in air or water temperature). In addition, experimental studies or predictive models may provide clues as to how several climate factors (temperature, precipitation pattern) may interact. However, it is important to recognize from the start that because many climate factors and interacting species are changing simultaneously, species may show very complex responses, and thus it is often very hard to categorize relative risk. Predictions of responses to change and the relative vulnerability of species become even more uncertain when we try to put them in the context of all of the other stressors that [3.16.218...

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