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Number of insects decreases by 78% since 1989

© Belga
Changes in land use, loss of habits and increases in nitrogen and pesticides have all contributed to declining insect population numbers.
© Belga

A German entomologist’s association has been taking scientific measurements of insect populations, in a nature reserve situated in north-west Germany, from 1989 to 2013. They have thus noted a decrease in population numbers of 78% over the 24-year period.

The results of their research were published in the journal Science. This was indicated yesterday Tuesday by Natuurpunt (the Flemish counterpart of Natagora).

During its research, the German club used, the so-called “Malaise trap” technique. The equipment involved bears a resemblance to a tent. All insects that venture, by chance, into it land in an alcohol solution.

Thus in 1989, between one to one and a half kilograms of insects were caught in this way in flowering meadows.

In contrast, only 300 grams of such insects were caught in 2013.

Diversity has also decreased. In 1989, 143 species of hoverfly (from the fly family) were seen, compared to 104 in 2013.

Wim Veraghtert from Natuurpunt, says changes in land use and loss of habitats, in particular, explains this decrease. “The quality of remaining habitats is also placed under a a lot of pressure by the quantity of nitrogen reaching such areas, as well as the pesticides used, the impact of which is difficult to establish.”

He goes on, “Add climate change to the mix and the result is a deadly cocktail for the insect population.”

Insects fulfil various roles. They are pollinators (which is necessary to ensure biodiversity), predators of other insects (such as the greenfly), or even prey for numerous animals.

The Brussels Times