Predicted changes in the functional structure of earthworm assemblages in France driven by climate change

Abstract

AbstractAimSpecies shift their ranges as a consequence of climate change, hence modifying the structure of local assemblages. This may have important consequences for ecosystem functioning in the case of ecosystem engineers such as earthworms, especially when community restructuring leads to an alteration of their functional diversity. Here, we aimed to model the potential modification of the functional diversity of French earthworm assemblages in a context of climate change.LocationMetropolitan France.MethodsWe fitted boosted regression trees to earthworm data collected using a standardized protocol across France in the 1960s. We used model projections constrained by a macroecological model of species richness to predict the composition of earthworm assemblages in the present and in two scenarios of climate change and two future time periods. We coupled these results with a large set of species traits to calculate predicted changes in functional diversity, which we summarized by ecoregion.ResultsModels predicted a clear decline in functional richness between the period of sampling and nowadays which are expected to continue in the future, with substantial differences depending on ecoregions and on whether species will be able to disperse or not. However, predicted changes in functional evenness and divergence are much weaker, suggesting that climate change will not affect all facets of functional diversity in the same way.Main ConclusionsOur results mostly pointed to a potential reduction of the functional richness of earthworm communities in the future, but this predicted loss of diversity could be weaker if species are able to colonize new suitable sites or to persist in microclimate refugia. There are concerns, though, that these changes lead to an alteration of soil processes and of the ecosystem services they provide.