Ecological status of Swiss streams insufficient according to study

Small streams and rivers form the largest part of Switzerland's 65,000 kilometre-long network of watercourses. © KEYSTONE / GAETAN BALLY

The ecological status of Swiss streams is inadequate, according to a study. In over 70% of 99 streams analysed, researchers from the aquatic research institute Eawag found no insect larvae or other pesticide-sensitive small organisms.

Most of the streams analysed on the central plateau, in parts of the Jura region and in the floors of major valleys therefore only fulfilled their role as a habitat for animals to a limited extent, Eawag reported on Monday. In only approximately 20% of the sites is the biotic community in near-natural condition and appropriate to the location, according to the article.

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As stated in the article, small streams and rivers form the largest part of Switzerland’s 65,000 kilometre-long network of watercourses. They are therefore an important habitat for many species of fish, insect larvae, small crustaceans, and worms.

The researchers used the so-called macrozoobenthos, which includes insect larvae, as an indicator of how good the water quality is. Individual species in this community react very sensitively to changes in their environment, for example to pollutants or obstructions in and around water bodies or to land use in the catchment area.

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According to the scientists, this enables them to draw conclusions about the quality of the waterways.

According to the Eawag study, streams whose structure had been heavily modified, such as streams that were straightened, were particularly affected.

In addition, a large proportion of farmland, fruit crops, and vineyards in the catchment area of the streams had a particularly negative impact on the occurrence of sensitive organisms, according to the study published in the specialist journal “Aqua & Gas”.

The study emphasises the urgency of measures to protect and enhance these bodies of water, wrote the institute.

Adapted from German by DeepL/dkk/mga

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