Study shows dramatic decline in German insect population

Kristen Gonzales
Октября 20, 2017

The number of flying insects in Germany has been dropping at an "alarming" rate that could signal serious trouble for ecosystems and food chains in the future, scientists say. "This decrease has always been suspected but has turned out to be more severe than previously thought", Hallmann said in a statement.

The researchers, led by Caspar Hallmann of Radboud University in Nijmegen, Netherlands, said it was unclear why the numbers in Germany have declined so sharply, but concluded that neither landscape nor climate change are likely to be the cause.

Goulson was part of a team of European scientists who studied population levels in 63 nature reserves across Germany from 1989 to 2016 by setting up malaise traps that captured more than 1,500 samples of flying insects.

The meticulous sampling of flying insects over so many sites and so many years yielded a dataset that is unique in the world, de Kroon told Seeker. Many flying insect species travel long distances, going across country borders and even oceans. "Yet, this dramatic decline has occurred". Flying insects were trapped in so called malaise traps and the total biomass was then weighed and compared.

"However", he continued, "when you get an over 75 percent decline in total insect biomass, you know this is not due to a few or vulnerable species".

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The decline is independent from habitat type and can not be explained by changes in weather, land use or habitat characteristics.

The study did not pinpoint a reason for the precipitous drop, but Goulson notes that many nature preserves are surrounded by agricultural lands. "They're even crucial in waste control - most of the waste in urban areas is taken care of by ants and cockroaches". They also suggested "agricultural intensification", including the use of pesticides, increased use of fertilizers and year-round tillage, could be a "plausible cause" for the decline.

"These surrounding areas inflict flying insects and they can not survive there", said Caspar Hallmann, researcher at Radboud. The study provides that 60% of birds need insects for food and almost 80% of plant life relies on them for pollination.

"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.

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