Ural Federal University: Amphibian Population Decreased Rapidly in the Last Three Years

Biologists have recorded severe simultaneous drops in the numbers of three different species of frogs and newts – rare and widespread. The largest population declines occurred among juveniles, but the scientists noted that adults and egg clutches were also affected. The description and results of the study are published in the journal Conservation Science and Practice.

“We believe that a wide range of anthropogenic adverse factors combined with natural fluctuations are responsible for the population decline. Among the causes are global warming, pathogenic infections, habitat loss and exposure to agro-industrial chemicals. But the main reason is drought: reduced precipitation led to a shortage of water in reservoirs and increased water temperature, which ultimately affected the amphibian population,” explains Vladimir Vershinin, co-author of the work, Head of the Department of Biodiversity and Bioecology of Ural Federal University, Head of the Laboratory of Functional Ecology of Terrestrial Animals of the Institute of Plant and Animal Ecology of Ural Branch of Russian Academy of Science.

Scientists monitored the number of amphibians (frogs and newts) from 2018 to 2020 in ponds and parks in Italy, Germany and Russia. In Russia, the study was conducted in Ekaterinburg and the surrounding areas of the city. As a result of observations, scientists found that in Italy, the number of grass frogs (in Russia it is a red-listed species) has steadily decreased: from 2018 to 2019, it decreased by 40 percent, and from 2019 to 2020 – by 46.7 percent.

In Germany, only one of the eight amphibian species showed no signs of population decline. The highest percentage of losses was in the Common Frog (Hyla arborea) and two newt species (Lissotriton vulgaris and Triturus cristatus). In Russia, juvenile numbers declined by 31.7 percent from 2018 to 2020, exacerbating an ongoing negative trend that began decades ago, scientists notes.

“The negative trend is especially noticeable for two species, the Common Newt (Lissotriton vulgaris) and the Siberian salamander (Salamandrella keyserlingii), whose numbers decreased by 38.2 percent and 84.2 percent respectively. Regardless of the reasons, the decline in the amphibian population may have negative consequences not only for these species, but also for others, even widely distributed ones,” says Vladimir Vershinin.

As the scientist explains, the decrease in the number of amphibians can have serious consequences, since amphibians are the link between the biogeocenoses of land and freshwater reservoirs, control the number of a large number of invertebrate pests, which, unlike birds, they consume indiscriminately, switching to more numerous. The larvae of tailless amphibians feed on dead organic matter as well as microscopic algae, preventing water blooms.

Meanwhile, the global decline of amphibian populations has become a serious problem over the past 30 years. As scientists had previously thought, the rate of decline of amphibian populations would increase by the end of the century. However, research results show more and more signs that this process speeds up already in the last few years.