Studies on the development of insects in Switzerland and around the world often come to the conclusion that species diversity has drastically decreased. The results are particularly worrying for insects on land, which perform important tasks as pollinators in the ecosystem. As part of the Blue-Green-Biodiversity research initiative launched by WSL and Eawag, Friederike Gebert investigated how the diversity of aquatic insects in Swiss watercourses has changed in recent years.
Her results, which she and other researchers published in the journal Biology Letters published show a somewhat different picture: in none of the families and genera examined did the number of species common in Switzerland decrease between 2010 and 2019. On the contrary: heat-loving insect species have increased at medium to higher altitudes, such as the mayfly Baetis rhodani. Insect families that are not sensitive to pesticides, such as midges, have also increased. Species numbers of insects sensitive to pesticides, such as most caddisflies and stoneflies, have remained stable.
Even species that prefer cooler conditions like the mayfly Baetis alpinus, have not disappeared despite rising temperatures. For their study, the researchers used data collected at 438 locations in Switzerland as part of Biodiversity Monitoring Switzerland. “We were very surprised by the clear results with stable and increasing numbers of species over a period of only ten years,” says Gebert. It should be noted, however, that biodiversity monitoring primarily records the common and widespread species; no statements can be made with this data on rare species.
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