Assessing climate change vulnerability using demographically informed species distribution models

Grassland ecosystems originally dominated central North America but have been extensively altered by agriculture, fire suppression, and urbanization. These land use changes are not occurring in isolation, and many lowland areas are experiencing rapid changes in temperature and precipitation, a result of climate change. Modern land use and climate change represent critical threats to many grassland-dependent fauna, but little is known as to why these species are sensitive to climate variability and which populations are most vulnerable to future environmental change. Henslow’s Sparrow (Ammodramus henslowii) is an obligate grassland bird that historically bred in tallgrass prairie, but due to widespread habitat loss, is now dependent on “surrogate” grassland habitats (e.g., hayfield and pastures). We developed a Climate Change Vulnerability Assessment approach to evaluate demographic sensitivities of Henslow’s Sparrow to climate variability at a large landscape scale, and the potential impacts of future land use and climate change scenarios on populations throughout the species’ range. To do so, we created a database of published nest success rates for Henslow’s Sparrow and linked those rates to environmental parameters in a spatially and temporally explicit manner. We used these estimates along with other demographic components (e.g., survival estimates, territory size, density, site fidelity) to build spatially explicit population models within HexSim, a cell-based population modeling framework, to incorporate climate data to simulate historic and future population projections. Using this approach, we can produce demographically informed species distribution models projecting the relative impact of future climate change on Henslow’s Sparrow populations and distribution. This approach will also allow us to incorporate management scenarios into the models to evaluate large landscape conservation of grassland birds.