How do dispersal rates promote distribution shift of biodiversity in the face of global changes?

Background/Question/Methods

Terrestrial biodiversity and ecosystem services face numerous anthropogenic pressures among which land-use and climate changes are of major concern. Because the viability of populations depends on their ability to shift their range, the present work assesses the role played by dispersal rates in a comparative framework. Birds constitute a very illustrative taxon with respect to these issues: the consequences of global changes on birds’ community dynamics include both declining abundance of some species and distribution shifts towards higher latitudes. This shift is lagging behind with respect to climate, and the causes behind this lag are little explored.  We investigated this issue using data from a large scale bird survey (Breeding Bird Survey) over Metropolitan France monitoring 37 species (farmland specialist species and generalist species) over 7 years. We first estimated for each species the dispersal rates between regions using a dynamic meta-population model taking into account seven land-uses and thirteen climate variables. Then, for each species, outputs from the previous models are used to project populations range shift under different land-use and climate scenarios.

Results/Conclusions

At the national scale and for each species, this model makes it possible to estimate values of dispersal rate. We found that dispersal rate is an important parameter to explain variations in abundance. In other words, to appropriately model variations in abundance of a species within a region we need to include climatic and land-use variables but also the abundance of this species in the neighboring regions and their dispersal rate. We found a significant interaction between habitat specialization and dispersal rate. While dispersal rate had no influence on specialists populations trends, there was a positive correlation for generalists (slope =0.78, P = 0.01). Finally this original work allows to simulate distribution shifts for each species, under both climatic and land-uses scenarios, taking into account their dispersal rate. Levels of dispersal can have strong influence on models predictions such as niche modeling. Visual representation with maps could help spread these results to policy makers / land managers to improve management plans.