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Intensive farming is one of the biggest factors contributing to biodiversity loss. While prior research has focused primarily on the effects of habitat loss and fragmentation, intensive farming also has other environmental effects, including the use of pesticides in agricultural environments.

A in Science of The Total Environment looked into the effects of two pesticides on the Glanville fritillary butterfly, which often lives in such environments. The study aimed to determine how short-term exposure in the larval stage affects the growth rate of larvae and the reproductive success of adult butterflies.

The study focused on one fungicide and one herbicide, as well as a mixture of both. The fungicide in particular increased the mortality rate of larvae and slowed down development already after a short exposure time. The mixture of the two substances reduced the harmful effects of the fungicide on larval development, although it remained slower than in larvae that received a control treatment. It also negatively affected the reproductive capacity of adult butterflies.

"Pesticides are widely used in agriculture, and new products are constantly being introduced to the market. In spite of environmental regulations and laboratory testing for toxicity levels, we know relatively little about how different pesticides affect non-target species in the wild," says Doctoral Researcher Ulla Riihimäki from the Faculty of Biological and Environmental Sciences.

Systematic monitoring does not extend to residues in nature

According to the researchers, different pesticide types can cause very different reactions in non-target organisms.

"It's important to more closely monitor the quantity of pesticides in nature and further investigate their potential effects on wildlife. EU legislation should also pay more attention to protecting terrestrial wildlife alongside preventing waterbody contamination," Riihimäki points out.

"The use of pesticides is strictly regulated, and the approval of new active substances always requires a risk assessment. The concentration of pesticide residues in food is monitored, and they must not exceed the reference values. To a degree, pesticide residues are also monitored in waterbodies and groundwater. However, residues found in nature are not systematically monitored, and it is difficult to estimate the quantities to which various wildlife species are exposed," says Lotta Kaila, DSc (Agriculture and Forestry), one of the authors of the article.

"Further research and closer monitoring are necessary to protect biodiversity and ensure that pesticide use does not harm organisms that it does not specifically target," says Professor Marjo Saastamoinen, whose research group conducted the study.