Biodiversity conservation in archaeological sites: a Mediterranean-wide assessment

Archaeological and monumental sites function as important reservoirs of plant diversity, yet their conservation role remains largely unrecognized. Across the Mediterranean, they function as overlooked reservoirs of plant diversity and should be recognized as part of the conservation estate. Here we present the first basin-wide assessment of plant diversity in AMSs, surveying 69 sites across 17 countries. We documented 3,337 vascular plant taxa, including 113 strictly endemic (3.4%) and 233 regionally endemic taxa (7.0%), together with 573 taxa listed on international Red Lists and 679 on national Red Lists. Plant richness was driven by the regional species pool rather than site area, indicating that AMSs capture a substantial fraction of surrounding biodiversity regardless of their size. These findings challenge the dominant view of archaeological sites as cultural assets threatened by vegetation and instead identify them as hybrid nature–culture systems that already deliver measurable biodiversity outcomes. We argue that legal protection of cultural heritage has unintentionally generated an “umbrella effect” for biodiversity, and that recognizing AMSs as Other Effective Area-based Conservation Measures could substantially expand the conservation estate, with major implications for European and global biodiversity goals.