The effect of habitat fragmentation on climate-driven community changes

(Poster)

Yoan Fourcade
yoan.fourcade@slu.se

Swedish University of Agricultural Sciences, Department of Ecology, Sweden
,
Erik Öckinger
Swedish University of Agricultural Sciences, Department of Ecology, Sweden

DOI: 10.17011/conference/eccb2018/107403

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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.

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INTRO:
The authors approach the important question of how landscape features - namely habitat amount and level of fragmentation - are related to species turnover in ecological communities facing climate change. To approach this question, they study the community turnover of European butterfly communities and associate it with the amount and fragmentation of semi-natural habitat. They further dig into species specific traits to assess their sensitivities to fragmentation. They find that landscape features affect species ability to track their climatic optimum.
MERITS:
How climate change and habitat fragemntation jointly influence natural systems is indeed a pressing question of contemporary conservation and ecological research (e.g. Mantyka-pringle et al., 2012; Oliver & Morecroft, 2014; Holyoak & Heath 2016). Depending on the species' dispersal abilities and/or levels of specialization, habitat fragmentation and habitat loss can severely accentuate the effects of climate change by reducing the potential for species to track their climatic optima. I believe the authors therefore approach one of the most central questions of contemporary conservation.

Also, the fact the authors take a multispecies / community level approach adds to the generalizability of the results to a great degree and is therefore likely to interest a broad audience.
CRITIQUE:
The abstract starts a bit slow and much space is devoted to describing the rather simple process of species turnover with changing climate. This could have been reduced to about a half. On the other hand, more space could have been devoted to introducing results and discussing their significance. To say that "these analyses revealed the impact of landscape factors on the ability of species to shift their distribution in response to climate change" is a bit vague and does not allow the reader to make any interpretation of the findings. How did the landscape influence? Also, it is said that species traits were incorporated in the analysis, but no mention of species specific differences in the response are mentioned. A single sentence could have fixed this.
DISCUSSION:
The question is interesting and topical, the approach of using multispecies data is an ambitious one and is likely of much interest to the more ecology research related audience of ECCB. However, it is difficult to say how interesting their findigs are, as this is not really emphasized in the abstract (although the scarcity of ecological data is!).

The effect of habitat fragmentation on climate-driven community changes