Pesticides endanger biodiversity in waters

Even small doses of pesticides reduce the number of species by 42 percent

Insect species such as these damselfly are particularly threatened by pesticide inputs. © André Künzelmann / UFZ
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The harmful effects of pesticides are reaffirmed: they have reduced the biodiversity in European waters by up to 42 per cent, even at concentrations considered safe by European standards. This has resulted in the study of an international research team. The pesticide effect is therefore particularly affected by important links in the food chain. The result shows that the current tests do not capture the actual consequences of the pesticides, here must urgently be improved, the researchers warn in the journal "Proceedings of the National Academy of Sciences".

Although pesticides, for example from agriculture, are among the best ecotoxicologically studied and regulated groups of pollutants. However, it was previously unknown whether and to what extent and at what concentrations their use causes species losses in water bodies. Mikhail A. Beketov and Matthias Liess from the Helmholtz Center for Environmental Research (UFZ) in Leipzig have now studied this together with their colleagues. For their study, they compared species diversity in rivers at several locations - including the Hildesheimer Börde near Braunschweig, in South Victoria in Australia and in Brittany in France. They examined three different levels of pesticide contamination: untouched, slightly contaminated or heavily polluted.

Biodiversity dropped by 42 percent

The result: The researchers found significant differences in the species abundance of invertebrates. In the heavily contaminated European sites, biodiversity was 42 percent lower than the unaffected. In Australia, insect species declined by 27 percent between pesticide-contaminated sites on the one hand and low-contaminated and untouched ones on the other. Disappeared were at the polluted sites thereby several groups of living things, which are particularly vulnerable to pesticides. These include, in particular, representatives of stoneflies, mayflies, caddisflies and dragonflies.

These organisms are among the most species- and individuals-rich colonizers of European rivers, streams and streams. They are also important members of the food chain, they feed on numerous fish. They only allow the biological diversity of aquatic habitats by ensuring a regular exchange between surface and groundwater as an indicator of water quality.

Damage even at supposedly harmless concentrations

Of particular concern to the researchers is that the devastating effects of pesticides on microorganisms have already been detected at concentrations considered safe under current European legislation. This indicates that the statutory maximum amounts do not adequately protect the biodiversity of invertebrates in rivers. New approaches that combine ecology and ecotoxicology are therefore urgently needed. display

LeiderThe present practice of risk assessment is unfortunately similar to a highway ride blindfolded, the kotoxikologe Matthias Liess to consider. For so far, the approval of pesticides is based only on experimental work in the laboratory and artificial kosystemausschnitten. For an in-depth assessment of the ecological effects of these chemical substances, however, the existing concepts urgently need to be compared with the reality in the field. Pesticides will always have effects on ecosystems, no matter how rigid the protection concepts are. But only if validated assessment concepts are used, can a realistic assessment be made of which ecosystems must be protected at what levels. "The threat to pesticide biodiversity has apparently been underestimated, (Proceedings of the National Academy of Sciences, 2013; doi: 10.1073 / pnas.1305618110)

(Helmholtz Center for Environmental Research - UFZ, 18.06.2013 - NPO)