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Mechanisms for species responses to climate change: Are there biological thresholds?


Climate change-driven shifts in distribution and abundance are documented in many species. However, in order to better predict species responses, managers are seeking to understand the mechanisms that are driving these changes, including any thresholds that might soon be crossed. We leveraged the research that has already been supported by the Northeast Climate Adaptation Science Center (NE CASC) and its partners and used the latest modeling techniques combined with robust field data to examine the impact of specific climate variables, land use change, and species interactions on the future distribution and abundance of species of conservation concern. Moreover, we documented biological thresholds related to climate variability and change for critical species in the Northeastern and Midwestern U.S. Our objectives were to identify the primary drivers (e.g., climate change, urban growth) of species distribution changes in the Northeast; examine the nature of species landscape capability change over time to identify potential thresholds; determine how changing temperatures and snowpack characteristics will drive species interactions; determine the sensitivity of tree and bird responses to the magnitude, variability, periodicity, and seasonality of temperature and precipitation under climate change in the eastern U.S.; develop projections based on discrete climate triggers that have been linked to known biological thresholds; and identify how discrete climate triggers such as extreme events will correlate with known biological thresholds. Focal species included eastern tree species, songbirds, moose, Canada lynx, snowshoe hare, and southern pine beetle. Major outcomes include 1) knowledge of the mechanisms that drive projected changes in the distribution of vulnerable wildlife and tree populations that will enable better assessment of vulnerability and adaptation planning; and 2) improving how these results are conveyed to stakeholders by identifying understandable responses in the form of thresholds.



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