Assessing Climate Change Vulnerability of Species in Northwestern North America
Case, Michael Jordan
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Climate change affects plants and animals in myriad ways. However, not all species respond similarly, making climate-informed management more difficult. Therefore, managing species in the face of climate change requires an understanding of which species are most susceptible and what factors will increase their vulnerability. Vulnerability can be seen as being a function of sensitivity, exposure, and adaptive capacity. Using these three components, vulnerability assessments can identify (1) which species are most vulnerable, (2) why those species are vulnerable, and (3) which factors can be potentially leveraged to reduce vulnerability. Here, I present three chapters that explore these vulnerability components and offer a methodology for assessing vulnerability to climate change. The first chapter uses a combination of scientific literature and expert knowledge to assess the relative climate-change sensitivity of 196 plant and animal species in the Pacific Northwest region of North America. I found that although there are highly sensitive species in each of the taxonomic groups analyzed, amphibians and reptiles were, as a group, estimated to be more sensitive to climate change than the other taxa we considered. I also demonstrate how sensitivity and confidence information can be combined to prioritize management action and future research needs. Such information will increasingly enable managers to identify which species are more sensitive and identify the key aspects that can be leveraged to increase resilience in the face of climate change. The second chapter focuses on a novel approach of modeling species distributions. Here, I demonstrate an approach to projecting climate impacts on species distributions that draws on information from both empirical and mechanistic models. These mechanistically-informed models projected less suitable environmental space than our unrefined models for the majority of species analyzed. Although the two modeling approaches projected similar trends of expansion and contraction for most species, the locations of expansion and contraction differed by approach. The results of this study demonstrate that informing empirical niche models with mechanistic model output can reduce the likelihood of over predicting suitable environmental space. Future projections from these refined modeling approaches offer insight into the location of these suitable areas and which species may be better able to persist in a changing climate. The third chapter incorporates sensitivity, exposure, and adaptive capacity to assess the relative vulnerability to climate change of 11 tree species in western North America. I used a multivariate approach to quantify elements of sensitivity to climate change, exposure to climate change, and the capacity to adapt to climate change. Of the 11 species that were analyzed, Garry oak (<italic>Quercus garryana</italic>) was determined to be the most vulnerable, largely due to its relatively high sensitivity. By contrast, big leaf maple (<italic>Acer macrophyllum</italic>) was determined to be the least vulnerable of the 11 species, largely due to its adaptive capacity. Our analyses provide a framework for assessing vulnerability and for determining why some species will likely be more vulnerable than others. Such information will be critical as natural resource managers and conservation practitioners strive to address the impacts of climate change with limited funds.
- Forestry