How the Swiss insect world has changed

For the study published on Tuesday, a research team led by Agroscope analyzed records of 811 species from the years 1930 to 2021, as the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) announced on Tuesday.

The result: the number of species of deadwood beetles declined until 1960, stabilized thereafter and has returned to the level of 1930 since the 2000s. In contrast, the diversity of butterflies declined until the 1980s and has not recovered since then. Today, there are on average 12 percent fewer butterfly species nationwide than in 1930. The decline was particularly pronounced on the Central Plateau (29 percent) and in the northern foothills of the Alps (13 percent).

Intensification of agriculture

The greatest declines occurred during the period of intensification and mechanization of agriculture between 1950 and 1980. Fertilizers, pesticides and the structural standardization of the landscape had a negative impact on habitats. The removal of dead wood to increase yields in forestry also deprived many beetle species of their livelihood.

Climate change had the opposite effect. According to the study, rising temperatures favored many warmth-loving species that have been able to spread since the 1980s. The majority of deadwood beetle species benefited from this. They also benefited from major storms such as "Vivian" in 1990 and "Lothar" in 1999, which created large quantities of deadwood.

Researchers: "More intensive efforts needed"

The researchers also attribute the trend reversal for some species to the increasing environmental protection efforts since the 1990s. These include more biodiversity-friendly forest management and various agri-environmental programs. The partial recovery shows that the measures are having an effect primarily in the forest, explained study co-author Kurt Bollmann from the WSL in the press release. "However, for numerous specialized species, such as many butterfly species, even more intensive efforts are needed."

In addition to Agroscope and WSL, the national data center info fauna, the Swiss Ornithological Institute Sempach, the Research Institute of Organic Agriculture (FiBL), ETH Zurich, the Universities of Basel and Zurich and the Spanish Estación Biológica de Doñana were also involved in the study.