LB 6-46 - Birds ringing the bell on climate change in the Northern Canadian boreal forest

Background/Question/Methods:

Climate change is considered one of the most critical threats to biodiversity. High-latitude ecosystems - such as Canada's boreal forest - are predicted to experience abrupt climate-induced changes, which may reduce the total forested area by 42%. Boreal birds are susceptible to both direct and indirect effects of climate change, and several studies have predicted northward shifts in species distributions as the climate warms. These shifts, paired with potential ecozone contraction, may lead to decreased abundance of many species as habitats shift and change. To anticipate species-specific, spatially explicit changes to boreal bird densities under climate change, we evaluated density projections for 72 bird species based on integrated models of climate change and forest dynamics in the Northwest Territories (NWT), Canada, over the next 70 years. The objectives of this study were to 1) identify and contrast boreal bird "winners" and "losers" over short and long-term forecasts and 2) evaluate spatial variation in responses among three contrasting Global Circulation Models (GCMs). We used SpaDES, an open modeling toolkit in R, to integrate our model and ensure our work is open, reusable, and testable. Predicted densities generally changed little over the short term (2031).

Results/Conclusions:

Only one forest-associated species (Gray-cheeked Thrush) decreased consistently under all three GCMs. The few increases were concentrated in the south and were not uniform across GCMs. In the long term (2091), 11 species were projected to have increased densities among all GCMs; six of these were forest-associated, two were wetland-associated, and three belonged to the 'other' group. According to our forecasts, 37 bird species will increase their abundance by more than 50% by 2091 in at least one GCM; only 16 species were projected to decline by more than 25%. Increases tended to progress from south to north; spatial patterns of decrease included range rescission instances from high (White-crowned Sparrow) and low latitudes (Palm Warbler). Integrating forest change and climate models to forecast spatially explicit responses of bird density provides an important advance for vertebrate biodiversity under climate change.