The Angel is not yet out of the discussion about the groundbreaking insect study

Anyone who wants to fight a scientific twist can best have a long breath – certainly when the discussion takes place on paper, in a prominent magazine like Nature. The Nijmegen researchers Caspar Hallmann and Hans de Kroon and their colleagues experienced this when their comments on another scientific article were finally published this week, after a very long time.  »

At the end of 2023 received the Dutch of a German-swiss biologists teamled by Jörg Müller, criticism Their groundbreaking 'Krefeld study' from 2017. In it Hallmann and De Kroon had concluded that the flying insect biomass, so the total weight of all flying insects, had decreased by more than 75 percent in 27 years. The same article also stated that there was no clear cause. Earlier it would be a 'death by a thousand cuts', in which fragmentation of habitat, pesticide use and climate change play a role.

Nonsense, Müller and his colleagues considered: according to them, the decreases were simply due to shifts in weather conditions. In recent decades, the winters became warmer and dryer where the insects remained active for longer (which allowed them to fall prey to enemies) or the eggs dried out. On the other hand, the insect position could immediately boost again with increasingly wet spring conditions.

The Nijmegen biologists found that reasoning far too short again. After all, all kinds of species came together in the traps in which the insects were collected, with very different weather preferences. In their eyes it was hardly conceivable that all insects would be so deteriorated by mere shifts in the weather. « Haha, » Müller responded to the criticism by e-mail at the time. « This is just good science. All our data and codes are publicly available. « 

Statistically unreliable

But now, a year and a half after the part of Müller CS, Save the crown and Hallmann back with its own publication Nature. The title: Weather Anomalies Cannot Explain Insect Decline. According to them, the statistical model of the German-Swiss team reflects a false, meaningless relationship between weather changes and insect decrease; Observed increases in insect biomass would not get through the weather but due to incomparable sampling locations and the use of a different type of fall.

De Kroon, in an e-mail: “There is no doubt that climate change has effects on survival of insects and shifts between species. Work on this only starts. But with these 'big steps, quickly at home' method, the effects cannot be proven, and that distracts attention from major threats such as pesticides. « 

At one point, all researchers do seem to agree with each other: decline in insect biomass is a complex subject, and better cooperation is needed. Hopefully that conclusion gets the sting from the discussion.

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