Insects are becoming fewer and fewer – and the specialists are disappearing the fastest

In a special issue of the journal Biology Letters, researchers from Europe, America and Australia draw attention to a growing problem: the number of insects, but also insect species, is decreasing and becoming more uniform.

“Just as landscapes are becoming more similar, for example in farmland, insect communities are also becoming more similar,” said special edition co-editor Martin Gossner of the Swiss Federal Institute for Forest, Snow and Landscape Research WSL in a recent paper. rack.

It is not climate change that is the main culprit here, but intensive land use. However, due to global mobility and global warming, more and more non-native invasive species are spreading and threatening native species. The invasive species are especially successful in intensively used agricultural areas with damaged ecosystems.

“Insect specialists in particular are dying out, while generalists survive,” says Florian Menzel of the Johannes Gutenberg University in Mainz. Those species that are typical for one or the other habitat are disappearing.

Of the examples cited in the special issue, according to WSL, the decline in bumblebee species has led to a decline in plants that rely on certain bumblebee species for pollination. Decreasing biodiversity reduces the stability of ecosystems: not only are fewer plants pollinated, it is also more difficult to control pests. And less food is available for insectivorous birds and other animals. The decrease in insects is therefore also related to the decrease in certain birds.

The WSL’s Gossner says action needs to be taken now: “It’s important to upgrade the landscapes and bring more diversity back into the habitats.” In the forest there is a need for more structures such as dead wood, old trees with shelter and places with a lot of light, but also for more diversity in the landscape in general. In agricultural lands, hedges and shrubs are a central element for insect diversity.

Protected areas also need to be connected, only then can species migrate from one habitat to another, for example to move from areas that have become inhospitable due to global warming to cooler regions higher up or further north.

The authors also write that more attention should be paid to reducing the spread of invasive species through the global movement of goods and travel. For example, the introduction of insectivorous fish in Brazil led to a sharp decline in freshwater insects. (kiss) (bzbasel.ch)