• Energy Research

Abstract Multiple studies revealed an effect of climate change on biodiversity by investigating long‐term changes in species distributions and community composition. However, many taxa do not benefit from systematic long‐term monitoring programmes, leaving gaps in our current knowledge of climate‐induced community turnover. We used data extracted from the Global Biodiversity Information Facility to characterize community reorganization under climate change for nine animal taxonomic groups (ants, bats, bees, birds, butterflies, earthworms, frogs, rodents and salamanders), which, for most of them, had never been studied before in this regard. Using a presence‐only community temperature index (CTI), reflecting the relative proportion of warm‐ and cold‐adapted species, we tested whether and how species' assemblages were affected by climate change over the last 30 years. Across Europe and North America, we observed an average increase in CTI, consistent with a gradual species turnover driven by climate change. At the local scale, we could observe that the composition of most species assemblages changed according to temperature variations. However, this change in composition always occurred with a lag compared to climate change, suggesting that communities are experiencing a climatic debt. Results suggest that anthropization may play a role in the decoupling between the change in CTI and the change in local temperature. The results of our study highlight an overall thermophilization of assemblages as a response of temperature warming. We demonstrated that this response may exist for a large range of understudied terrestrial animals, and we introduced a framework that can be used in a broader context, opening new opportunities for global change research.

Climate and land-use change are recognised as the two main drivers of the ongoing reorganisation of Earth’s biodiversity, but understanding precisely their role in shaping species’ distributions and communities remains challenging. In mountainous regions, we typically observe an uphill shift of species’ altitudinal ranges caused by increasing temperatures, but it is difficult to predict how this process interacts with land-use change. Here, we replicated an inventory of bumblebees that took place in the 1960s in Norway. Focusing on subalpine areas, we reported changes in species richness and community temperature index (CTI), a measure of the relative proportion of warm- and cold-adapted species, at low and high altitude. Using aerial photographs and meteorological data, we tested the relationship between climate and land-cover changes and changes in species richness and CTI. We observed an overall increase in CTI consistent with a gradual species turnover driven by climate change. There was on average an increase in species richness at high altitudes, while low-altitudes communities tended to become less species-rich. Moreover, we observed a negative correlation between species richness and temperature and precipitation trends, suggesting a detrimental effect of climate change. Thanks to the replication of an historical inventory, we were able to show evidence for an effect of climate, and possibly land-cover, change on subalpine bumblebee assemblages. These results can contribute to a better understanding of the processes driving biodiversity changes in subalpine areas in a context of global climate and landscape changes

AbstractHabitat fragmentation may present a major impediment to species range shifts caused by climate change, but how it affects local community dynamics in a changing climate has so far not been adequately investigated empirically. Using long‐term monitoring data of butterfly assemblages, we tested the effects of the amount and distribution of semi‐natural habitat (SNH), moderated by species traits, on climate‐driven species turnover. We found that spatially dispersed SNH favoured the colonisation of warm‐adapted and mobile species. In contrast, extinction risk of cold‐adapted species increased in dispersed (as opposed to aggregated) habitats and when the amount of SNH was low. Strengthening habitat networks by maintaining or creating stepping‐stone patches could thus allow warm‐adapted species to expand their range, while increasing the area of natural habitat and its spatial cohesion may be important to aid the local persistence of species threatened by a warming climate.

AbstractTranslocation experiments can be used to study the factors limiting species' distributions and to infer potential drivers of successful colonisation during range shifts.To study the expansion dynamics of the butterflyPyrgus armoricanusin southern Sweden and to find out whether its distribution was limited by climate, translocation experiments were carried out within and 50–60 km beyond its natural range margin. Populations were monitored for 8 years following the translocation.Although most translocation attempts failed,P. armoricanuswas able to survive in two sites north of its current range limit. One of them eventually led to expansion and establishment of a viable metapopulation. Translocation success appeared to be independent of latitude, suggesting that climate is not the main factor determining the current northern distribution limits of this butterfly.Population growth and secondary spread in the expanding population were positively related to patch area and connectivity, while local habitat quality seemed to be less important.The successful translocation and the importance of a well‐connected patch network suggest that the current distribution ofP. armoricanusis limited by its low dispersal ability combined with the fragmentation of its habitat, making it unlikely to track its changing climatic niche. Assisted migration could be an effective tool for such species, but long‐term evidence for its effectiveness is not yet available.

Abstract Prediction of species distributions in an altered climate requires knowledge on how global‐ and local‐scale factors interact to limit their current distributions. Such knowledge can be gained through studies of spatial population dynamics at climatic range margins. Here, using a butterfly (Pyrgus armoricanus) as model species, we first predicted based on species distribution modelling that its climatically suitable habitats currently extend north of its realized range. Projecting the model into scenarios of future climate, we showed that the distribution of climatically suitable habitats may shift northward by an additional 400 km in the future. Second, we used a 13‐year monitoring dataset including the majority of all habitat patches at the species northern range margin to assess the synergetic impact of temperature fluctuations and spatial distribution of habitat, microclimatic conditions and habitat quality, on abundance and colonization–extinction dynamics. The fluctuation in abundance between years was almost entirely determined by the variation in temperature during the species larval development. In contrast, colonization and extinction dynamics were better explained by patch area, between‐patch connectivity and host plant density. This suggests that the response of the species to future climate change may be limited by future land use and how its host plants respond to climate change. It is, thus, probable that dispersal limitation will prevent P. armoricanus from reaching its potential future distribution. We argue that models of range dynamics should consider the factors influencing metapopulation dynamics, especially at the range edges, and not only broad‐scale climate. It includes factors acting at the scale of habitat patches such as habitat quality and microclimate and landscape‐scale factors such as the spatial configuration of potentially suitable patches. Knowledge of population dynamics under various environmental conditions, and the incorporation of realistic scenarios of future land use, appears essential to provide predictions useful for actions mitigating the negative effects of climate change.

AbstractMarginal populations are usually small, fragmented, and vulnerable to extinction, which makes them particularly interesting from a conservation point of view. They are also the starting point of range shifts that result from climate change, through a process involving colonization of newly suitable sites at the cool margin of species distributions. Hence, understanding the processes that drive demography and distribution at high‐latitude populations is essential to forecast the response of species to global changes. We investigated the relative importance of solar irradiance (as a proxy for microclimate), habitat quality, and connectivity on occupancy, abundance, and population stability at the northern range margin of the Oberthür's grizzled skipper butterflyPyrgus armoricanus. For this purpose, butterfly abundance was surveyed in a habitat network consisting of 50 habitat patches over 12 years. We found that occupancy and abundance (average and variability) were mostly influenced by the density of host plants and the spatial isolation of patches, while solar irradiance and grazing frequency had only an effect on patch occupancy. Knowing that the distribution of host plants extends further north, we hypothesize that the actual variable limiting the northern distribution ofP. armoricanusmight be its dispersal capacity that prevents it from reaching more northern habitat patches. The persistence of this metapopulation in the face of global changes will thus be fundamentally linked to the maintenance of an efficient network of habitats.