The number of insect species has decreased by almost one third, according to a study by the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the University of Bern.
Over the last 25 years it has become very apparent that the number of insects in the world has declined. Dr Sebastian Seibold said: “Previous studies, however, either focused exclusively on biomass, i.e. the total weight of all insects, or on individual species or species groups. The fact that a large part of all insect groups is actually affected has not been clear so far.”
Dr Seibold led a large-scale biodiversity study with his international research team in order to survey the large number of insect groups in Brandenburg, Thuringia and Baden-Württemberg, Germany, between 2008 and 2017.
Collecting data from more than 1 million insects at 300 sites, researchers were able to prove that many of the 2700 species that were investigated are in decline. First author of the study, Dr Seilbold, said: “Before our survey it was unclear whether and to what extent forests were affected by the insect decline as well.”
“A decline on that scale over a period of just 10 years came as a complete surprise to us – it is frightening, but fits the picture presented in a growing number of studies,” says Wolfgang Weisser, professor of Terrestrial Ecology at TUM and a co-initiator of the cooperative project.
“To decide whether it is a matter of the more mobile forest-dwelling species having more contact with agriculture, or whether it has something to do with living conditions in the forests, further study will be needed,” said the WSL researcher Dr. Martin Gossner.
“This result illustrates the great added value of carefully coordinated interdisciplinary long-term research, which allow to document and understand insect shrinkage much more accurately and comprehensively than individual studies,” says Markus Fischer, Professor of Plant Ecology at the University of Berne and the main initiator of the research programme.