Regional variation in climate change winners and losers highlights the rapid loss of cold-dwelling species

AimsClimate change is known to drive both the reshuffling of whole assemblages and range shifts of individual species. Less is known about how local colonizations and extinctions of individual species contribute to changes at the community level. Our aim was to estimate the contribution of individual species to a change in community composition attributed to climate change and to relate these species-specific contributions to species' commonness, climatic niche characteristics and life history traits most likely to influence species sensitivity to climate change. LocationSweden. MethodsFocussing on birds, we analysed changes from 1998 to 2012 in the Community Temperature Index (CTI), a measure of the average climatic niche of a community. Using a jackknife approach we assessed the contribution of individual species to the temporal trend in CTI in four different regions across Sweden, controlling for habitat distribution. We further tested whether species contribution was related to population trends and rarity to identify species most vulnerable to climate change. ResultsCommunity Temperature Index had increased over time with the greatest gains occurring in the north of the country, reflecting the larger temperature increases in this area. Changes in the regional CTI were driven both by warm-dwelling species colonizing new sites and by extirpations of cold-dwelling species. Furthermore, the community changes were influenced by both rare and common species. At the same time, the distribution changes of a large number of species were seemingly unaffected by climate change. Main conclusionsBoth range expansion and contractions contributed to the relative increase of warm-dwelling species in Swedish bird communities. We successfully identified the climatic impacts on some of Sweden's rarest species, including cold-dwelling species in the mountainous north. Our approach may be an efficient tool to use when characterizing the impacts of climate change on species and communities.