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Study shows: More than 75 percent decline over three decades in total flying insect biomass in protected areas

Bild: qay / pixelio.de

Global declines in insects are a big topic when it comes to the status of biodiversity. The German Entomological Society Krefeld with its experts is a recognised institution in this field. Using a specially developed study design and so-called malaise traps, the Society measured total insect biomass over almost three decades in 63 nature protection areas in Germany - and recorded a decline of more than 75 percent. The first publication of the Krefeld researchers in 2013 kicked off a broad debate.

Now Caspar Hallmann from Radboud University in Nijmegen (Netherlands) and colleagues have re-evaluated the data and confirmed the findings. They estimate a seasonal decline of 76 %, and mid-summer decline of 82 % in flying insect biomass over the 27 years of study.

Why is that, what are the driving mechanisms behind this development? There are working hypotheses, but no conclusive explanations, and the scope of the investigation as well as the available data do not allow conclusive statements.The decline, the researchers say, is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics are unlikely explanatory factors. Rather, agricultural intensification (e.g. pesticide usage, yearround tillage, increased use of fertilizers and frequency of agronomic measures) may form a plausible cause.

The protection sites in which the traps were placed are of limited size, located in the fragmented West-European landscape, with almost all of them (94 %) surrounded by agricultural fields. Thus, they may well be strongly affected by agricultural practices.

It's really is high time to get to the bottom of this alarming development and take countermeasures. This is also clearly evident from the results of the World Biodiversity Council IPBES, which was launched in 2012 to develop recommendations for policy-makers. Last year, its report "Pollinators, Pollination and Food Production" was adopted by the governments involved. 

Publication in PLOS ONE:

Hallmann CA, Sorg M, Jongejans E, Siepel H, Hofland N, Schwan H, et al. (2017) More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLoS ONE12(10): e0185809. doi.org/10.1371/journal.pone.0185809

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