Pond quality is key to saving Europe's declining amphibians

European ponds are essential habitats for amphibians, which are experiencing dramatic declines across Europe due to habitat loss and degradation. In two complementary studies from the EU PONDERFUL project, we examined over 350 ponds across multiple European countries, spanning diverse climates and landscapes. We employed cutting-edge environmental DNA (eDNA) metabarcoding, a technique that detects multiple amphibian species from simple water samples, to assess species richness, including rare and protected ones.Shallow ponds with excellent condition emerged as biodiversity hotspots. The highest richness occurred in low-nutrient, fishless, intermediate-sized, shallow ponds located in warmer, wetter regions. Local factors, such as chlorophyll-a concentration (indicator of nutrient pollution), outweighed broader influences like precipitation or temperature. Protected species particularly benefited from these pristine conditions, underscoring the urgent need to mitigate pollution and invasive species.Our findings highlight ponds' overlooked role in conservation policies. Targeted actions, such as preserving natural water flows, reducing nutrient runoff from agriculture, and removing barriers or invasive fish, can amplify amphibian populations continent-wide. For instance, restoring degraded ponds to mimic natural, low-nutrient states could safeguard vulnerable species while enhancing ecosystem resilience against climate change. These evidence-based strategies equip policymakers and land managers to protect Europe's freshwater biodiversity.