How much can Mediterranean coastal dune plant communities change in just 10–15 years?

Details

Tracking changes in plant communities over time is a core aim of temporal ecology and a shared priority of global conservation agendas, especially in threatened ecosystems. Mediterranean coastal dunes contain some of Europe's most threatened habitats. Yet studies of recent biodiversity changes in these systems that considered multiple facets of diversity and different aspects of community structure were missing.

Using data from a resurveying study, the researchers provided a first comprehensive, habitat-based assessment of multiple facets of change over 10–15 years in threatened Mediterranean coastal dunes. They quantified taxonomic changes—changes in which plant species make up the communities—and functional changes using indices capturing multiple biodiversity features. They examined trends at both community and species levels.

They compared observed biodiversity changes across habitats to look for evidence of generalized biodiversity loss, and across diversity facets to infer the potential loss of unique functions. They tested the significance of these changes using a null model. Their prediction was that many communities would show large compositional shifts and biodiversity loss beyond expectations, with differences among habitat types.

The results revealed severe shifts in communities' taxonomic profiles, mostly driven by non-random species loss. There was also little overlap in functional space between surveys, implying large changes in both community structure and the ecological strategies represented in the habitats studied. Together with the disappearance of approximately 23% of historical plots and substantial losses in focal species, these findings suggest intense degradation processes in coastal dune habitats, particularly on the upper beach and on shifting dunes.

Synthesis: The study provides the first evidence of large, often non-random taxonomic and functional changes in Mediterranean coastal dune plant communities over a surprisingly short period. It advances knowledge of recent changes in these endangered ecosystems and identifies the habitat types most at risk, helping to guide future conservation and management. The researchers call for future research to test the potential drivers of these changes more precisely.