Insect death – starvation with full stomach

When the so -called Krefeld study was published in 2017, their results were dismissed by the public, politics and themselves. In North Rhine-Westphalia and Rhineland-Palatinate, insects had been caught for almost 30 years, and a loss was found by more than three quarters. Hardly anyone had expected such a sensitive loss.

The main ludios for insect deaths were identified: the pesticides of agriculture, the sealing of the area through streets and settlements, the change in temperature through climate change and increasing light pollution, which impossible for the insects the spatial orientation. Depending on the affected interest group, one reason is increased and the other downplayed. The conventional agriculture, which is often referred to as the main cause – A global survey of three years ago put their share in insect death to 46 percent – only a year later was happy about a published in the specialist magazine “Nature” Study of the University of Würzburg, which instead gave the main debt to the weather fluctuations. The Bavarian Farmers’ Association immediately headed up euphemistic and incorrect: Krefeld’s study almost completely refuted.

Farmers’ association such as chemical industry plays equally well in the cards that the causes mentioned, which are probably responsible for mass dying, can be difficult to differentiate from each other. The fact that the area seal has an impact on the insect decline sounds logical, only how is scientific proof to be provided? And from what amount of pesticides does it become so harmful that entire insect groups can no longer recover? Too many influences on the test field act, such as a field area, that a clear, scientifically clean statement can be made about what caused the change in insect population.

The situation in the conca was completely different. The almost 5000 soccer fields in the US state of Kansas enjoys the status of a biosphere reserve and is owned by Kansas State University. Settlements or even a farmhouse, none, there are no streets there. But what is plentiful is the rest of the original high grass prairies, which once covered the North American continent over a large area before the European settlers civilized the landscape. And this is exactly where a unique project started in 1996. For over 22 years, they examined the change in the nutrient content of the grass plants that grew unaffected by people and farm animals. Six years later, the scientists decided to take into account the parts of the prairie that are taken into account by free bison herds. Finally, the scientists Ellen Welti and Michael Kaspari took over the project and evaluated the extensive data records. The Result was impressive.

More mass, fewer nutrients

In the three decades, the entire plant biomass had increased by 60 percent. The praire command obviously seemed to thrive. However, when Welti and Kaspari examined the plants, a paradox revealed. The nutrient content of the plants did not remain the same or even increased, and to the astonishment of the two scientists, he had decreased rapidly. In the case of nitrogen, the shrinkage was still the slightest at 42 percent, potassium and phosphorus were reduced by more than half and sodium could only be detected ten percent in the plants. Only the content of magnesium was remained unchanged as a percentage. Instead, something else had increased significantly: the carbon content. Carbon (c), as the name suggests, is in carbon dioxide (CO₂) contain that the plants absorb from the atmosphere in order to be able to grow. In the observed period from 1996 to 2017, the CO took₂-S content in the atmosphere strongly -from around 360 to 406 parts per million (ppm).

For comparison: in 1955 there were still 314 ppm. The same CO₂-In the previous years, it took around twice as long. For plant growth, the atmospheric carbon dioxide increase was always classified as a positive effect: climate change as a natural fertilizer, according to the hopefully assumed downside of a dark medal. Accordingly, Melissa Pastore, ecologist at the University of Minnesota, undertook accordingly successful attempts to this assumption and published her results in 2018 in a globally noticed Study.

Acceptance of the grasshopper population

But in addition to the plant biomass, Welti and Kaspari examined something else in the Hochgrasprärie in the middle west: the orthopteras, the locusts living in this area. It is astonishing 44 different species in the Prairie conca to the Flint Hills. Uninfluenced by pesticides and intensive agriculture, area sealing and use by humans as well as in a food that has risen over the past few decades, would the jumping herbivores have to be the happy exception of the otherwise so serious insect death?

However, the measurements showed the exact opposite. In the 22 years observed, the population of grasshoppers decreased by 36 percent, whereby the values ​​between the bison and the unwrehended area hardly differ. So although the food supply for the grasshoppers increased by 60 percent, their number was reduced by more than a third. How was that possible? The reason sounds cruel: the grasshoppers starved with a full stomach. They were fed up with the plants, but they lacked the necessary amount of nutrients. The grasshoppers fed to a certain extent as if people only eat fast food – through food with many empty energies.

Further cause of insect death

If the new study by Welti and Kaspari is also confirmed in other regions of the earth, it will add a sensitive reason for the insect death to date. “Although the study is robust, weather fluctuations were also taken into account, some species could be able to adapt better than others,” suspects Roel van Klink from the German Center for Integrative Biodiversity Research in Leipzig. “However, which this could be and whether an adaptation or evolving in the necessary short time is possible, that cannot yet be said.”

However, if the effect of increased carbon enrichment in the plants is confirmed while taking the minerals at the same time, the insects would have a disaster. Because if the past, still relatively slightly increased CO₂-The values ​​in the atmosphere already get insects too few nutrients and that makes their populations break in drastically, how will it be in the next 20 to 30 years? Because in all likelihood, the carbon dioxide concentration will continue to rise sharply. Van Klink draws a dark picture. »Climate change will not disappear again in the foreseeable future. It will be technically impossible to the necessary quantities of CO₂ to filter out of the atmosphere in order to undo the effect of increased carbon enrichment in the plants. «

Studies in other regions necessary

Currently, further open space experiments in order to deepen, confirm or correct the results of the Welti and Kaspari study can be counted on one hand. Van Klink is planning the first German experiment of this kind, which has so far been to put a special focus on insects. And the time is pushing. Insects are the basis for the functioning of our ecosystems. Fruits, vegetables, nuts are dependent on their pollination. Insects are also food for other living things. Even if most of us cannot find insects cute, we should urgently start lobbying for you. Because Welti and Kaspari made another strong population loss, which may touch us emotionally more than the decline of insects. The grassland singing birds went back even more than the grasshoppers. Her population collapsed by more than half, 53 percent.

The article has been read by the German Center for Integrative Biodiversity Research and all statements made have been confirmed.