Aims Climate 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.Location Sweden.Methods Focussing 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.Results Community 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 colddwelling 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 conclusions Both 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.

The local spatial congruence between climate changes and community changes has rarely been studied over large areas. We proposed one of the first comprehensive frameworks tracking local changes in community composition related to climate changes. First, we investigated whether and how 12 years of changes in the local composition of bird communities were related to local climate variations. Then, we tested the consequences of this climate-induced adjustment of communities on Grinnellian (habitat-related) and Eltonian (function-related) homogenization. A standardized protocol monitoring spatial and temporal trends of birds over France from 2001 to 2012 was used. For each plot and each year, we used the spring temperature and the spring precipitations and calculated three indices reflecting the thermal niche, the habitat specialization, and the functional originality of the species within a community. We then used a moving-window approach to estimate the spatial distribution of the temporal trends in each of these indices and their congruency with local climatic variations. Temperature fluctuations and community dynamics were found to be highly variable in space, but their variations were finely congruent. More interestingly, the community adjustment to temperature variations was nonmonotonous. Instead, unexplained fluctuations in community composition were observed up to a certain threshold of climate change intensity, above which a change in community composition was observed. This shift corresponded to a significant decrease in the relative abundance of habitat specialists and functionally original species within communities, regardless of the direction of temperature change. The investigation of variations in climate and community responses appears to be a central step toward a better understanding of climate change effects on biodiversity. Our results suggest a fine-scale and short-term adjustment of community composition to temperature changes. Moreover, significant temperature variations seem to be responsible for both the Grinnellian and Eltonian aspects of functional homogenization.

The spatial tracking of climatic shifts is frequently reported as a biodiversity response to climatic change. However, species' range shifts are often idiosyncratic and inconsistent with climatic shift predictions. At the community scale, this discrepancy can be measured by comparing the spatial shift in the relative composition of cold- vs. warm-adapted species in a local assemblage [the community temperature index (CTI)] with the spatial shift in temperature isotherms. While the local distribution of climate change velocity is a promising approach to downscaling climate change pressure and responses, CTI velocity has only been investigated on a continental or national scale. In this study, we coupled French Breeding Bird Survey data, collected from 2133 sites monitored between 2001 and 2012, with climatic data in order to estimate the local magnitude and direction of breeding season temperature shift, CTI shift, and their spatiotemporal divergence - the local climatic debt. We also tested whether landscape characteristics that are known to affect climate velocity and spatial tracking of climate change mediated the climatic debt on the local scale. We found a clear spatial structure, together with heterogeneity in both temperature and CTI spatial shifts. Local climatic debt decreased as the elevation, habitat diversity, and the naturalness of the landscape increased. These results suggest the complementary effects of the local topographic patterns sheltering more diverse microclimates and the increasing permeability of natural and diversified landscape. Our findings suggest that a more nuanced evaluation of spatial variability in climatic and biotic shifts is necessary in order to properly describe biodiversity responses to climate change rather than the oversimplified descriptions of uniform poleward shifts.

Aim Protected areas (PAs) are the mainstay of our conservation strategies. While they may succeed in locally preventing species and habitat degradation due to human activities, their ability to mitigate the impacts of climate change on biodiversity is still debated. We assessed whether community and species responses to climate change were related to PAs by testing three main predictions: (1) the thermal adjustment of community composition to temperature changes should be positively related to the proportion of PAs, (2) the species that benefit most from PAs should be less impacted by temperature change, and (3) the species a priori considered the most vulnerable to global change should be even more sensitive to the mitigating effect of PAs. Location Mainland France. Methods Data from a long‐term, large‐scale standardized monitoring programme, recording annual changes in the abundance of 116 breeding bird species in France between 2001 and 2012, were used. Local temporal trends in spring temperature, community reshuffling and bird populations over the country were estimated with a moving window approach (2094 spatial windows). Generalized additive mixed models were then performed to relate these responses to the local proportion of PAs. Results Most PAs promote community adjustment to temperature changes. At the species scale, our results show that the more a species benefited from PAs, the less vulnerable it was to temperature changes. PAs were also more effective in mitigating the impact of climate change on the less common and northernmost birds. Main conclusion Protected areas do seem to mitigate climate change impacts on species and communities. Our study argues for the use of integrative frameworks at different biological scales to assess the usefulness and relevance of PAs faced with climate change and suggests that PAs remain key effective conservation strategies in a changing climatic world.

No abstract

Aim We disentangle three facets of species commonness (local abundance, geographical range size, degree of habitat generalization) to identify how species segregate along these axes and how each of these facets determines the relative functional originality of each species (i.e. the mean trait distance of a species with others). At the community level we test whether changes in the relative abundances of species with different levels of commonness contribute to the spatial and temporal dynamics of species assemblages and to the local trend in functional homogenization. Location France. Methods Data from the French Breeding Bird Survey from 2001 to 2012 were used to represent the yearly change in species abundances of 198 species over 2057 plots. Functional originality and three commonness indices were calculated for each species related to their geographical range, habitat generalization and specific local abundances. These species‐specific indices were then used to compute community‐weighted means of commonness and functional originality. Hierarchical partitioning was used to investigate the relationships between each of the three facets of commonness and functional originality. Generalized additive models were used to estimate the spatial and temporal trends of each community index. Results Species that are generalist and abundant but with a restricted range had higher functional originality. From 2001 to 2012, assemblages were increasingly composed of species with large ranges and of habitat generalists. The functional simplification of communities was mainly linked to the increase in species with large ranges and, to lesser extent, to a decrease in species with high local abundances. Main conclusions The decomposition of commonness into complementary facets is useful for describing the causes and consequences of biotic homogenization at large spatial scales. Functional simplification can occur during a short time period and is driven mainly by the greater success of species with large ranges.

Global changes are modifying the structure of species assemblages, but the generality of resulting diversity patterns and of their drivers is poorly understood. Any such changes can be detected and explained by comparing temporal trends in taxonomic and functional diversity over broad spatial extents. In this study, we addressed three complementary questions: How did bird taxonomic and functional diversity change over the past 40 years in the conterminous United States? Are these trends non-linear? Can temporal variations in functional diversity be explained by broad-scale changes in climate and vegetation productivity? We quantified changes in taxonomic and functional diversity for 807 bird assemblages over the past four decades (1970-2011) considering a suite of 16 ecological traits for 435 species. We found increases in local bird species richness and taxonomic equitability that plateaued in the early 2000's while total abundance declined over the whole period. Functional richness, the total range of traits in an assemblage, increased due to the rising prevalence of species with atypical life-history strategies and under-represented habitat or trophic preferences. However, these species did not trigger major changes in the functional composition of bird assemblages. Inter-annual variations in climate and primary productivity explained the richness of bird life-history traits in local assemblages, suggesting that these traits are influenced by broad-scale environmental factors, while others respond more to more local drivers. Our results highlight that a comparative analysis of the multiple facets of functional diversity can raise novel insights on processes underlying temporal trends in biodiversity.

No abstract