Efficacy of Current Protected Areas in the US for Conserving Winter Bird Diversity

Seasonally snow-covered ecosystems support a unique diversity of cold-adapted plants and animals that are increasingly threatened by winter climate change. Protected areas provide the first line of defense for species threatened by modern climate change. However, current protected areas in the United States are often biased towards 1) preserving specific landscape features, 2) areas unsuitable for agriculture (e.g., mountain slopes), or 3) regions that support high species richness during the breeding season (summer). As such, the current network of protected areas may fail to preserve cold-adapted species and ecosystems exposed to a rapidly changing winter environment.

We combined >3 million bird observations (2005-2020) from eBird, a global citizen science program, with remotely sensed metrics of winter conditions to map high-resolution, winter-specific bird distributions across the US. We modelled >400 winter bird distributions with Adaptive Spatiotemporal Exploratory Models, which account for non-stationarity in species-environment responses and adapt to variation in data density. We mapped bird richness (# of species) hotspots for cold-adapted and total winter bird diversity to identify overlap between richness hotspots. We coupled our winter-specific bird distributions with a protected areas database to assess the efficacy of the current protected areas network for conserving winter bird diversity. We found that hotspots of cold-adapted and total winter species richness rarely overlapped; hotspots of cold-adapted species were located primarily in mountainous regions of the western US whereas total bird richness peaked in the southeastern US, Mississippi River floodplains, and central valley of California. The current network of protected areas provided sufficient spatial coverage for most cold-adapted bird ranges in the western US, but not for cold-adapted birds in the eastern US. There were striking mismatches between total winter bird diversity hotspots and protected areas due to a lack of conserved lands in agricultural regions throughout the US. Using novel remotely sensed metrics of winter conditions, we successfully modeled richness hotspots for winter-adapted birds and identified existing gaps in the protected areas of the United States for conserving winter bird diversity.