Insects can benefit from warming, but only in cold regions | NOW

Insects also appear to be slowly moving towards the poles under the influence of climate change. For European countries, this means that some insects are increasing in number, while others are declining (extra) fast. This can be concluded from a new German researchwhich was recently published in the trade journal Global Change Biology†

Overall, insects are not doing well. That is true in Europe, and just as much in North America.
People who remember holiday trips, thirty or forty years ago, know that the windshield of the car had to be washed every few 100 kilometers because of all the insects that were shoveled along the way.

Today we almost don’t experience that anymore. There’s even a scientific term for it: the windshield phenomenon, or “windshield phenomenon.” That’s anecdotal evidence, based on people’s memories. It is more difficult to determine exactly how quickly insects deteriorate.

In 26 years, 76 percent of our insects disappeared

That changed in 2017. A Nijmegen research group received 26 years of continuous measurements of flying insects in northern Germany. Their conclusion: the number of insects has fallen by more than three quarters – and that within protected natural areas.

Motorists need to wash their windows less often, but ecologists speak of a collapse at the base of the food chain: countless other species are in turn dependent on insects. And it is feared that the decline is not over.

There it becomes important to also understand the causes, and that is another step more difficult. The most important in Europe are probably over-fertilization, desiccation and the use of insecticides (agricultural poisons).

But what about climate change? The Nijmegen researchers had not looked specifically at this in 2017, but suspected that the influence would be relatively small.

Southern German dragonflies, grasshoppers and butterflies

A collaboration of several German universities has now looked into this in more detail. They also managed to obtain a large amount of measurement data, which were collected over a period of more than 40 years by volunteers in the southern German state of Bavaria. They randomly recorded the numbers of 230 species of butterflies, dragonflies and grasshoppers.

This shows that the numbers of flying insects are also declining on average in the south of Germany. But when the group led by the Technical University of Munich looked more closely at the data, they saw that in all groups there were also species that actually increased – which they call the “heat lovers.”

The most obvious example is the bright red fire dragonfly. Until the 1990s, it did not occur in Bavaria at all, but has become widely distributed more than twenty years later.

Tropical insects affected by warming

That’s actually not very surprising. Europe has warmed considerably in recent decades, and this dragonfly species is very common in Africa and the Mediterranean. The Netherlands is now the new northern border of the fire dragonfly’s distribution area.

For example, in cold or temperate areas, species can also increase due to climate change, because heat-lovers move towards the poles. Does this also mean that climate change is good for insects? Then it is better to look at data from the tropics – where no species migrate to seek cooling.

Here too, the available measurement data show that insects are declining rapidly – and climate change appears to be the main cause, together with intensification of agriculture. Climate change is therefore not ‘good’ for insects. But locally there are species that can benefit – especially in cold regions.

Incidentally, there are also insects that really like the cold – and in our regions therefore deteriorate extra quickly due to climate change. According to the German researchers, this applies to, among other things, the green mountain locust, the venwit-snouted dragonfly and Thor’s mother-of-pearl butterfly† Perhaps those species are doing better in Scandinavia in the meantime.