German nature preserves have lost 75 percent of their flying insects


While it is well documented that butterflies and bees have been disappearing in Europe and North America, the study in PLOS ONE is the first to document that flying insects in general have decreased by more than three-quarters across Germany since 1989.

To do so, they measured the total flying insect biomass, the weight of the insect catch, by using tent-like nets called Malaise traps.

For 27 years, researchers used insect traps placed in nature areas where many species commonly live.

"This study lumps all flying insects together", research teaching fellow in entomology at Sydney University's School of Life and Environmental Studies, Tanya Latty, said to CNN Thursday.

It then appears that plants, flying insects, and many birds - all of which have lives that are intertwined within their ecosystems - are decreasing in species diversity, if not in other respects.

Scientists believe the fact the declines were recorded in well-managed nature reserves makes the results even more troubling, as numbers outside them, where wildlife has less or no protection, are likely to be even worse.

At 82 percent, the decline of insects biomass during midsummer, when insects populations tend to peak, proved more severe than the annual average decline. Three years later, scientists are still trying to warn the public of the seriousness of the issue, calling the loss of wildlife a "biological annihilation" in a published paper.

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"As one of the few studies assessing overall biomass this study is a useful complement to the larger set of studies on specific groups of insects", writes John Losey, an entomologist at Cornell University in NY, in an email to The Scientist.

In the study, researchers conducted a "census" 60 nature reserves created in Germany over the past century.

"Therefore", de Kroon continued, "we can only assess the overall decline over the study period, and are not able to look into the temporal variability in the rate of decline". Instead, the researchers hypothesise that larger-scale factors must be involved, such as pesticides and agricultural intensification.

"As entire ecosystems are dependent on insects for food and as pollinators, it places the decline of insect eating birds and mammals in a new context", said researcher Hans de Kroon.

The exact causes of the decline are still unclear.

He added: "We need to do less of the things that we know have a negative impact, such as the use of pesticides".