dataset using data freely available at a national scale on agriculture intensity and landscape composition. We found that species richness increased with increasing proportion of herbaceous semi-natural elements; species dominance decreased with increasing crop diversity; the proportion of above ground nesting species and specimens increased as the intensity of agricultural practices decreased. Comparing the results obtained with identification to species level and those obtained with higher taxa or parataxonomic approaches, we found that the loss of taxonomic resolution resulted in the non-significance of some results on the effects of environmental variables on bee assemblage-level attributes. Our study suggests that identification to species level is of great importance to detect the effects of global change on bees and that an expert-assisted citizen science paradigm could provide relevant results to guide conservation measures at a national scale.

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International audienceThe Coussouls de Crau Nature Reserve is a xeric steppe providing a habitat for remarkable animals. Over the past centuries, this steppe has been partly destroyed and fragmented and has been reduced to 9,500 ha out of the 55,000 ha existing before the 16th century. Although this ecosystem is protected, 23 ha of natural habitat were nonetheless destroyed in 2006 during the construction of an underground pipeline. To mitigate potential future damage, an original experiment in restoration ecology was adapted and tested: the technique of hay transfer. The objective of this experiment was to find ways of accelerating steppe vegetation colonization on the soil over the buried pipelines by the reintroduction of steppe species. A factorial experiment was set up to test the effects of habitat characteristics, grazing, and hay transfer. The results obtained for 3 years after the experimentation setup are conclusive in favor of using hay transfer for the restoration of Mediterranean steppe ecosystem. Hay transfer has significantly increased the species richness on restored areas and has allowed the reintroduction of some typical steppe species. Among these species, we found a wide variety of annual grasses which play a key role in the recovery of steppe vegetation and provide food for sheep flocks. Sheep herding must be maintained during the ecological restoration of the herbaceous steppe community, because grazing significantly increases species richness on restored areas without changing species assemblies