Hidden losses of amphibians and dragonflies in Berlin's municipal water supply

A new study led by Museum für Naturkunde Berlin researchers reveals that Berlin's dragonfly populations have plummeted by over half since 1963, while frog, toad, and newt populations have declined by more than three-quarters since 1981. The research, part of the "Understanding Diversity—Exploring and Experiencing Nature" project, utilized two extensive datasets: the Berlin Dragonfly Database, containing nearly 24,000 observations since 1850, and the Berlin Amphibian Dataset, with over 16,000 records since 1970.

The study analyzed 16 regularly surveyed bodies of water across Berlin, from Grunewald forests to lakes in Köpenick. The data shows dragonfly numbers declining by an average of 51% from 1963 to 2023, and amphibian numbers falling by 76% from 1981 to 2022. Lead author Silvia Keinath notes that amphibians are more vulnerable due to their limited mobility and reliance on specific migration routes.

While dragonflies can fly to new water bodies, they too suffer from habitat loss and drying ponds. The study highlights that losing permanently dried water bodies, which occurred in 36 of the originally studied sites, could inflate the actual decline. The findings stress the importance of continuous, long-term biodiversity monitoring in urban areas like Berlin, where such data has been scarce due to lack of structured monitoring programs.