Getting the measure of the biodiversity crisis in Mediterranean coastal habitats

Abstract

1. Assessing temporal changes in plant communities is a core aim of temporal ecology and a shared priority of global conservation agendas which is particularly urgent in threatened ecosystems. Mediterranean coastal dunes harbour some of the most threatened habitats in Europe. Yet, surprisingly, studies capturing the recent temporal dynamics of biodiversity in these systems by accounting for multiple diversity facets and different aspects of community structure are missing. 2. Here, using data from a resurveying study, we provide a first comprehensive, habitat-based, multi-faceted assessment of recent (10-15 years) temporal changes in threatened Mediterranean coastal dunes. To this aim, we quantified taxonomic and functional changes in plant communities using indices capturing multiple biodiversity features, and we explored trends at both the community level and the species level. We compared observed biodiversity changes across habitats (to look for evidence of generalized biodiversity loss) and across facets (to infer the potential loss of unique functions), and tested their significance using a null model. Overall, we predicted large compositional shifts and biodiversity loss beyond expectations in many communities, although with differences among habitat types. 3. Our results reveal severe shifts in the taxonomic profile of the communities, mostly driven by a non-random species loss, and little temporal overlap in functional space, implying large changes in both community structure and ecological strategies of the investigated habitats. This, together with the disappearance of c. 23% of historical plots and with substantial losses in focal species, suggests that intense degradation processes are occurring in coastal dune habitats, particularly on the upper beach and on shifting dunes. 4. Synthesis. This study provides the first evidence of large, often non-random, taxonomic and functional changes occurring in Mediterranean coastal dune plant communities in a surprisingly short time-span. Along with furthering our knowledge of the recent dynamics affecting these endangered ecosystems, our results also pinpoint the types of habitats that are most at risk, helping to direct future conservation efforts and management. Future research should now be directed at more precisely testing potential drivers of these changes.

Mediterranean developed coasts: what future for the foredune restoration?

“…Limiting trampling damage through fences, boardwalks, and betterdesigned accesses to prevent visitors straying from the pathway have been proved to be a highly efficient management measure (Acosta et al 2013;Muñoz-Vallés and Cambrollé 2014;Prisco et al 2021). At present, Mediterranean coastal dunes are listed among the most threatened habitats in Europe, and they are in increasingly urgent need of ecological protection and restoration (Sperandii et al 2021). Reduction or prevention of human impacts on dunes must remain one of the main purposes in coastal dune management.…”

Proposals for improvement of Annex I of Directive 92/43/EEC: Sardinia

“…There is increasing evidence of the continuous loss and degradation of Mediterranean coastal habitats, particularly those located on dunes, affected by severe impacts from mass tourism (Sperandii et al 2021). Therefore, it is urgent to protect the remnant well-preserved dune habitats and those with average conservation status, supporting future conservation and restoration actions.…”

LOTVS: A global collection of permanent vegetation plots

“…Finally, to broaden the range of potential applications of LOTVS (and in line with what has been done by other global initiatives, see Bruelheide et al, 2019), we are planning to integrate it with information on environmental variables (climate, microclimate) and species functional traits. Such integration will eventually allow users complementary access to ancillary data crucial to explore the evolution of different facets of diversity over time (Monnet et al, 2014; Sperandii et al, 2021).…”