Impacts of climate change to breeding and migrating waterbirds in the Prairie Pothole Region

Abstract

The Prairie Pothole Region (PPR) of the north-central U.S. and south-central Canada contains millions of small prairie wetlands that provide critical habitat to many migrating and breeding waterbirds. Due to their small size and the relatively dry climate of the region, these wetlands are considered at high risk for negative climate change effects as temperatures increase. Using a bioclimatic species distribution modeling (SDM) approach, I explored the potential effects of climate change on 31 breeding waterbird species. The approach involved using a random forest modeling algorithm and downscaled climate data from outputs of two future General Circulation Models (GCMs). By the 2040’s, species were projected, on average, to lose 46% of their current habitat in the U.S. portion of the PPR. Species specific projected impacts ranged widely, with three species (Wilson’s Snipe, Sora, and Franklin’s Gull) projected to lose close to 100% of their U.S. Prairie Pothole habitats and two species (Killdeer and Upland Sandpiper) projected to gain habitat. Bioclimatic SDM approaches, however, have been shown to produce varying projections of species climate change impacts depending on methodological decisions including: choice of GCM, choice of climate covariates, level of collinearity among climate variables, and thresholding procedure used to convert probability values to binary occurrence values. I explored these and found that median projected range loss, across species, was 35%. However, projections for individual species varied widely, typically spanning from 100% range loss to range increases. The largest source of uncertainty was choice of GCM, followed by choice of climate covariate, then thresholding procedure. Level of collinearity contributed relatively little uncertainty. To understand the potential impacts of climate change to migrating shorebirds, I explored climate change sensitivity using historic records from a dry year and a wet year. Using historic data to explore climate sensitivity of migrating shorebirds in the PPR avoids many of the uncertainties of the bioclimatic SDM approach, and can yield insights helpful to guide adaptation planning for climate change. Using binomial generalized linear models, I found shorebirds shifted at the regional scale and selected landscapes with different characteristics in a dry year versus a wet year. This result indicates shorebirds are able to find habitat in the PPR under varying climate conditions, and supports a model of resilience for migrating shorebirds under climate change if wetlands in these varying landscapes are protected from drainage.