Groundwater overexploitation drives freshwater turtle declines in Doñana National Park

Legal protection alone rarely shields wetlands from basin-scale hydrological pressures. Doñana National Park (SW Spain), a UNESCO World Heritage Site, has progressively dried due to groundwater overexploitation, but the effects on its diversity have barely been explored. Here we used a snapshot resampling design to survey the park's pond network with standardized fyke nets in 1991–1994 and 2021–2024. We quantified abundance with capture–mark–recapture and assessed distribution changes. Abundance collapsed over three decades: the Mediterranean pond turtle Mauremys leprosa declined from 2805 (95% CI 2691–2937) to 1210 (949–1593) individuals (−56.9%), and the European pond turtle Emys orbicularis from 981 (864–1140) to 254 (186–388) (−74.1%). Distribution contracted sharply for E. orbicularis (−78.6%, from 42 to 9 occupied cells), whereas M. leprosa showed a smaller, non-significant reduction (−27.3%, 33 to 24 cells). Both species are now concentrated in a shrinking subset of long-hydroperiod ponds, indicating loss of functional habitat at landscape scale. These results demonstrate that strict protection has not maintained freshwater habitat quantity or quality in Doñana. Reversing declines requires urgent drastic reductions of groundwater withdrawal, restoring the pond network, and implementing hydrologically explicit monitoring and governance that link biodiversity outcomes to water-use decisions. Because presence–absence masked a > 50% abundance loss in M. leprosa , biodiversity assessments that ignore abundance likely underestimate declines in similarly degraded wetlands. Doñana's case, documented with long-term data, signals the urgent need to align protected-area management with basin-level water allocation to prevent local extinctions of its freshwater-dependent species.