Projected effects of climate change on the distribution and abundance of breeding waterfowl in Eastern Canada

As breeding areas are becoming warmer and wetter, climatic changes are likely to affect the distributions of millions of waterfowl in Eastern Canada. The objective of this study was to assess the potential effects of climate change on the breeding distribution and abundance of 12 common waterfowl species, by using a climate envelope modeling approach. Our response variables were species counts on 317 helicopter plots (25 km(2)) averaged over 22 years (1996-2017). We applied a covariate selection procedure to select the best subset of a panel of 170 climate covariates for each species, which we then used to fit quantile regression forest models. Climate change projections were applied to the waterfowl models to infer 2011-2100 abundances. From the projected abundances, we computed climate suitability indices that accounted for potential temporal mismatches between climate change and the biota, as well as the expected velocity of climate change. On average, with a maximum of 4 covariates per model, the variance explained was 41% for out-of-bag predictions. Overall, the magnitude of absolute projected changes peaked under the high greenhouse gas concentration trajectory (RCP8.5) and at the end of the century (2071-2100). Species-specific projections indicated that climate change would potentially increase the abundance and core distributions of 7/12 species, whereas 5/12 species would experience a decrease. In particular, large decreases were projected for Barrow's goldeneye, an imperiled boreal cavity nester. Our spatially explicit indices of climate suitability deliver important information for targeting areas to preserve waterfowl, ecosystems, and the services they provide.