The effect of habitat fragmentation on climate-driven community changes

Abstract

There is ample evidence that the ongoing climate change has large impacts on the distribution of species and on the composition of biological communities. Specifically, we known that communities respond to climate change by a gradual replacement of cold-adapted species by warm-adapted species that shift their range towards the poles and colonise the sites that became suitable for them. However, this process of species turnover is dependent on the ability of climate-tracking species to actually disperse in the landscape. Habitat fragmentation is a major impediment to dispersal. It usually results from habitat destruction that divides habitats into smaller and more isolated patches, therefore reducing population viability and connectivity between the remnant patches. As such, habitat fragmentation can potentially prevent species to colonise habitats that have otherwise become suitable as a result of climate change. As a consequence, increasing ecological connectivity has often been proposed as a strategy to reduce the negative impacts of climate change on biological diversity. However, in practice, there is almost no empirical evaluation of the effect of habitat connectivity on community response to climate change.

Here, we used long-term monitoring datasets of European butterfly communities to assess the effect of habitat fragmentation on community change driven by climate. We extracted the percentage area and an index of the spatial aggregation of semi-natural habitat around monitoring sites at increasing spatial scales. In addition, we calculated in each of these sites the temporal change in community temperature index (CTI), a measure of the relative proportion of cold- and warm-adapted species, and assessed the joint effect of habitat amount and aggregation on CTI trend. Moreover, using estimates of colonisation and extinction trends of individual species, we assessed the effect of various traits on their sensitivity to fragmentation in a changing climate.

Altogether, these analyses revealed the impact of landscape factors on the restructuration of communities in response to climate change. We especially demonstrated that the trend in CTI was positively correlated with the amount, and negatively correlated with the aggregation, of semi-natural habitat, mainly at large spatial scales. This result suggests that the turnover of species driven by climate change was facilitated by the presence of a large enough number of stepping-stone habitats that allow species to gradually shift their distribution. Such findings have important implications both for understanding the drivers of species distributions and community compositions and in a perspective of landscape management.