Bioindicator-based mapping of peatland potential in the Western Mediterranean-Atlantic Realm

Ecosystems with a naturally accumulated peat layer at the surface and wetlands with or without a peat layer dominated by a vegetation that may produce peat (hereafter 'peatlands' for simplicity) are critical assets in global change due to their large carbon content storage capacity and essential ecosystem services. A Global Peatland Assessment was initiated during the UNFCCC COP22; however, many countries still lack accurate peatland maps. This is particularly concerning in the Western Mediterranean, where these ecosystems are frequently overlooked or misclassified. To help address this issue, we developed predictive distribution models for vascular plant and bryophyte species typical of peatland-type systems in the Western Mediterranean. We identified 28 'indicator' mire-typical plant taxa and created a database using filtered data from six different data sources, including our own field surveys. Thirteen high-resolution spatial predictor variables, covering topographic, soil, and hydroclimatic factors, were selected to reflect potential relationships with species presence. For each species, a potential distribution model was built using MaxEnt software. The resulting potential-distribution maps were cross-validated, and models with an AUC score of ≥0.75 were classified into suitable or unsuitable areas. The species richness map aligned well with areas known to support peatlands. The indicator species-based mapping also suggests a broad potential for yet unrecorded peatlands in the Western Mediterranean, including small areas, particularly along the western and southwestern sandy coastlines and in the southern mountains.