Drivers of species richness and compositional change in Scottish coastal vegetation

Question: What are the main drivers of vegetation change within coastal dune and machair habitats and are these amenable to action to protect biodiversity at a local and national scale? Location: Coastal areas of Scotland. Methods: A national-scale, quadrat-based re-visitation survey was used to assess where changes were occurring in terms of species richness and composition. Regression trees and linearmixedmodellingwere used to identify themain drivers of change between 1976 and 2010. Results: There were losses of habitat to erosion (4.7% of previously visited quadrats) and development (2.3%). Species richness changes were largely positive where sand dune and machair habitats remain part of an agricultural management system in the Inner and southern part of the Outer Hebrides. Richness losses were driven by acidic deposition and reduced grazing. Compositional changes were less related to agricultural changes, climate change and pollutant deposition than species richness changes. Conclusions: Reintroduction of grazing to coastal areas appears to be a policy that would have positive effects on biodiversity, as would continued efforts to reduce atmospheric deposition and coastal planning that allowed for realignment as sediment supply decreases and sea level rise continues.