Berlin's dragonflies are down 51 percent, its amphibians 76, and 36 study ponds are simply gone

Researchers led by the Museum für Naturkunde Berlin have published long-run population trends for the city's dragonflies and amphibians in the journal Global Change Biology Communications ^[1]. Dragonfly populations fell by an average of 51 percent between 1963 and 2023, and amphibian populations fell 76 percent between 1981 and 2022 ^[2][3].

The numbers come from two datasets that had not been published before: the Berlin Dragonfly Database, with almost 24,000 observations going back to 1850, and the Berlin Amphibian Dataset, with more than 16,000 records going back to 1970, compiled by nature conservation organisations and specialist societies ^[4][5]. Two Berlin-based experts, Falk Petzold and Klaus-Detlef Kühnel, coordinate the data series, and the analysis was carried out under a project called "Understanding Diversity - Exploring and Experiencing Nature" ^[6][7]. Only 16 water bodies met the bar of being surveyed regularly and comparably over several decades, from forest lakes in Grunewald to bog waters in Köpenick and ponds in Marienfelde and Tegel ^[8]. The team used a Living Planet Index approach, which aggregates many individual population trends into one index of average change rather than absolute animal numbers, and which tolerates patchy underlying data ^[9].

The gap between the two groups is the finding worth sitting with. Over the 60-year dragonfly window the decline works out to roughly 1.2 percent a year; over the 41-year amphibian window it is roughly 3.4 percent a year, about three times faster ^[10][11]. Both groups live as larvae in water and as adults on land, and that dependence on two habitats is what makes them exposed ^[12]. Lead author Silvia Keinath says the direction of travel is no surprise but the severity of the amphibian loss is, and attributes it to mobility: frogs, toads and newts are far poorer travellers than dragonflies and suffer when routes between spawning grounds and terrestrial habitat are cut by roads, development or small waters drying out ^[13][14]. Dragonflies can fly to new ponds, though they too lose out when ponds dry too early ^[15].

The most consequential number is the one outside the index. Cross-referencing recent reports on Berlin's small water bodies, the team found that 36 of the water bodies originally studied have since dried up completely, partly because of falling groundwater levels and a lack of rainfall ^[16]. Those sites could not enter the index at all, because there was no continuous time series left to measure, so the authors state the real losses are probably larger than reported ^[17]. That is more than twice the number of waters that carried the published trend, drawn from a wider sampling frame ^[18].

Phys.org headlined the work as hidden losses "in Berlin's municipal water supply" ^[19]. The causal claim in the material is narrower than that: falling groundwater and low rainfall are named together, with no apportionment between abstraction and weather ^[16]. What the study does establish is that a single city can measure this if the records exist. Keinath notes such data has been rare in Berlin because there is no structured, long-term biodiversity monitoring in place ^[20].

Watch whether Berlin funds that monitoring, and whether groundwater drawdown gets separated from rainfall in the next round. A 2024 museum estimate found about 16 percent of species once native to Berlin have vanished since 1700 ^[21]; this work shows the decades of decline that precede that kind of number.