Prospects for Neotropical Forest Birds and Their Habitats Under Contrasting Emissions Scenarios.

Current and near future climate policy will fundamentally influence the integrity of ecological systems. The Neotropics is a region where biodiversity is notably high and precipitation regimes largely determine the ecology of most organisms. We modeled possible changes in the severity of seasonal aridity by 2100 throughout the Neotropics and used birds to illustrate the implications of contrasting climate scenarios for the region's biodiversity. Under SSP-8.5, a pessimistic and hopefully unlikely scenario, longer dry seasons (> 5%), and increased moisture stress are projected for about 75% of extant lowland forests throughout the entire region with impacts on 66% of the region's lowland forest avifauna, which comprises over 3000 species and about 30% of all bird species globally. Longer dry seasons are predicted to be especially significant in the Caribbean, Upper South America, and Amazonia. In contrast, under SSP-2.6-a scenario with significant climate mitigation-only about 10% of the entire region's forest area and 3% of its avifauna will be exposed to longer dry seasons. The extent of current forest cover that may plausibly function as precipitation-based climate refugia (i.e., < 5% change in length of dry periods) for constituent biodiversity is over 4 times greater under SSP-2.6 than with SSP-8.5. Moreover, the proportion of currently protected areas that overlap putative refugia areas is nearly 4 times greater under SSP-2.6. Taken together, our results illustrate that climate policy will have profound outcomes for biodiversity throughout the Neotropics-even in areas where deforestation and other immediate threats are not currently in play.