The exposure of Mediterranean key biodiversity areas to climate change and land-use modifications using CMIP6 future scenarios

Fabien Verniest and Thomas Galewski, Institut de recherche pour la conservation des zones humides méditerranéennes, Tour du Valat, Le Sambuc, 13200 Arles, France, Fabien Verniest, Romain Julliard and Isabelle Le Viol, Centre d’Ecologie et des Sciences de la Conservation (CESCO) - UMR 7204, Muséum National d’Histoire Naturelle, France

Background/Question/Methods
Conservationists have identified global biodiversity hotspots that are both important for biodiversity and heavily affected by anthropogenic pressures, and, within these regions, Key Biodiversity Areas (KBAs) i.e. sites where priority conservation measures should be implemented. However, in a context of global change, it is also crucial to target sites that will be both key for biodiversity conservation and strongly impacted in the next decades. Such strategy is achievable by anticipating the future location and intensity of anthropogenic threats, including but not limited to climate change. In this study, we assessed the exposure of Mediterranean KBAs to climate change and land-use modifications for the end of the 21st century. The Mediterranean region (3,814,495 km2 across 30 countries) shelters a high number of endemic species, has undergone major habitat loss and is projected to be strongly exposed to global change. Using future climate and land-use projections according to four CMIP6 scenarios, we calculated four exposure metrics that describe: (i) the local intensity of climate change, (ii) the relocation speed of climatic conditions, (iii) the local intensity of change in artificialness, and (iv) the difference in artificialness between future and current locations with similar climatic conditions.
Results/Conclusions
We found that KBAs were overall more exposed to climate change and land-use modifications than the rest of the study zone and adjacent areas. Although future scenarios differed in the intensity of exposure to land-use modifications and particularly to climate change, geographic patterns of KBAs exposure were similar between scenarios, with Turkish KBAs being the most exposed in three out of four scenarios. In contrast, the geographic patterns of KBAs exposure were greatly different from one metric to another, although the four exposure metrics were positively correlated with the elevation in almost all scenarios. We also found that most of the KBAs current climatic conditions would be concentrated in areas at higher elevation by the end of the 21st century. Our results emphasize the urgent need to implement conservation measures in KBAs as well as in high-elevation sites. We also demonstrate that the prioritisation of sites for such implementation would not be highly different from one scenario to another. Finally, as exposure assessments are highly dependent on the metric used, we recommend using multiple metrics but also other components of global change in combination with climate change when studying future anthropogenic impacts on biodiversity.