The Department of Defense (DoD) is responsible for managing threatened, endangered, and rare species inhabiting its properties. Predicting which of these species will need ongoing management due to changing climate conditions is valuable for planning and prioritizing natural resource management needs. The project team developed and tested an empirical protocol and theoretical framework for determining if target species are likely to become conservation reliant in the future.
The project team tested the empirical protocol using seven species: hydaspe fritillary butterfly (Speyeria hydaspe), Appalachian brown butterfly (Satyrodes Appalachia), western snowy plovers (Charadrius nivosus nivosus), red-legged frogs (Rana aurora and R. draytonii), Alaskan douglasia (Douglasia alaskana), Venus flytraps (Dionaea muscipula) and red-cockaded woodpeckers (Dryobates borealis). These species are either special status species or closely related surrogates for special status species managed on or near DoD properties. The project team used time series or space-for-time data and experimental manipulations to determine how climate influences the demographic rates of each species. They then used these relationships and downscaled global climate change models to build Spatially Explicit Environmental Driver (SEED) models to predict population level changes for each species under future climate scenarios. They also developed another tool, the Climate Contribution Index (CCI) that identifies the relative importance of different aspects of a species life history in shaping population responses to climate change.
Climate influenced demographic rates in numerous and complex ways. In many cases, demographic rates were affected by multiple climate variables, and it was not uncommon for the same climate variable to have opposing effects on different demographic rates. The project team found that projected population growth rates for the seven study species were typically either unaffected or positively influenced by future climate change. Only three of the 49 populations evaluated across all seven species were projected to have decreasing growth rates under future climate conditions. The populations most at risk for becoming conservation reliant due to climate change were those in the warmest parts of the species ranges. On the other hand, populations in the coolest parts of species ranges tended to benefit the most from projected changes in climate. Like the responses themselves, the demographic rate most responsible for shaping population responses to projected climate change varied among species and among populations within a species.
This project provides three main benefits to the DoD and other federal and nonfederal land managers. First, the project team identified many of the obstacles that need to be overcome when determining if a species is likely to be negatively (or positively) affected by projected changes in climate. Second, they developed and demonstrated the use of two tools to overcome those challenges. Both SEED models and CCI incorporate climate-demographic relationships throughout a species’ life cycle to: 1) predict how a species will respond to non-analogue climate conditions, and 2) to provide insight into which stages of the life cycle play shape that response. These tools can be used to prioritize future species management needs and evaluate potential mitigation actions. Third, they identified that many North American species will likely not require more intensive conservation efforts due to climate change. Management priorities aimed at existing threats, such as mitigating habitat destruction or invasive species are recommended. However, populations on the warmer edges of species ranges, particularly species with a large latitudinal or altitudinal range, are at greater risk, and thus should be evaluated more carefully.