Assessing the vulnerability of military installations in the coterminous United States to potential biome shifts resulting from rapid climate change

Climate change impacts to Department of Defense (DoD) installations will challenge future military mission and natural resource stewardship efforts by increasing vulnerability to flooding, drought, altered fire regimes, invasive species, etc. We developed biome classifications based on current climate for the coterminous United States using the Holdridge Life Zone system to assess potential change on DoD lands. We validated classifications using comparisons to existing ecoregional classifications, the distribution of major forest types and tree species in eastern North America. We projected future life zones for mid- and late century time periods under three greenhouse gas emission scenarios (low - B1, moderate - A1B and high - A2) using an ensemble of global climate models. To assess vulnerability of installations (n = 529), we analyzed biome shifts using spatial cluster analysis to characterize interregional variation and identified representative installations for subsequent landscape-level analyses. Although mean annual temperatures are expected to increase, installations located in the Northeast, Lake States and western Great Plains are likely to experience the largest proportional increases in temperature relative to historical conditions. Accordingly, forest and grassland communities at these installations managed to support a wide range of military training and environmental objectives may be adversely affected by altered disturbance regimes, heat and moisture stress. However, precipitation is projected to increase in the Northeast and Lake States mitigating some effects of increased atmospheric temperatures on biological communities. Given the uncertain response to climate change in the coming decades in different ecoregions, additional environmental and stewardship attributes are needed within a decision support framework to understand vulnerabilities and provide appropriate responses.