Ecological barriers mediate spatiotemporal shifts of bird communities at a continental scale

Abstract

Significance We used a unique long-term dataset on breeding bird counts covering an entire continent to quantify the influence of ecological barriers on climate change–driven bird community shifts. We show that ecological barriers exert a significant effect on the distance and direction of bird community composition shifts at the continental scale, with coastlines and elevation having the strongest influence. The results underscore the relevance of combining ecological barriers and community shift projections for identifying the forces hindering community adjustments under global change. The implications of this study are of direct relevance to scientists, decision-makers, and conservation practitioners. Abstract Species’ range shifts and local extinctions caused by climate change lead to community composition changes. At large spatial scales, ecological barriers, such as biome boundaries, coastlines, and elevation, can influence a community's ability to shift in response to climate change. Yet, ecological barriers are rarely considered in climate change studies, potentially hindering predictions of biodiversity shifts. We used data from two consecutive European breeding bird atlases to calculate the geographic distance and direction between communities in the 1980s and their compositional best match in the 2010s and modeled their response to barriers. The ecological barriers affected both the distance and direction of bird community composition shifts, with coastlines and elevation having the strongest influence. Our results underscore the relevance of combining ecological barriers and community shift projections for identifying the forces hindering community adjustments under global change. Notably, due to (macro)ecological barriers, communities are not able to track their climatic niches, which may lead to drastic changes, and potential losses, in community compositions in the future.