Antagonistic effect of natural habitat conversion on community adjustment to climate warming in nonbreeding waterbirds

While the impacts of climate and land use changes on biodiversity have been widely documented, their joint effects remain poorly understood. We evaluated how non-breeding waterbird communities adjust to climate warming along a gradient of land use change. Using mid-winter waterbird counts (132 species) at 164 major non-breeding sites in 22 Mediterranean countries, we assessed the changes in species composition during 1991-2010, regarding thermal niche position and breadth, in response to regional and local winter temperature anomalies and to natural habitat conversion. We showed that in response to the temperature increase, communities became relatively richer in warm-dwelling species, but less where natural habitat conversion occurred. At the sites affected by natural habitat conversion, the overall species richness decreased with time, while the abundance relatively increased for the species with a broader thermal niche, independently of their thermal affinities. The strong negative relationship between natural habitat conversion and community adjustment to temperature increases suggests an antagonistic interaction between climate warming and habitat change. Indeed, we found no evidence of community adjustment to climate warming when natural habitat conversion was higher than 5% over 15 years. These results underline the importance of habitat conservation in community adjustment to climate warming. Article impact statement: Waterbird communities do not adjustment to climate warming when natural habitat conversion is >5% over 15 years. This article is protected by copyright. All rights reserved.