Karlsruhe (dpa/lsw) – Experts warn of the effects of rising temperatures and lack of precipitation on earthworms and microorganisms in farmland and forest soil. Earthworms could face a difficult year due to lack of rain since May in the southwest. “Depending on how the weather goes on, things could get tight,” said agricultural biologist Otto Ehrmann. “Two dry years in a row would be very bad.” The earthworm population had already collapsed in the drought years of 2015 and 2018.
It is true that earthworms are quite well adapted to normal dry periods. They withdraw into deeper layers of the earth or live in deeper corridors anyway. Some bridged dry seasons in a kind of rigidity in cavities in the ground. However, the drought prevents them from feeding and reproducing. After a very dry summer, significantly fewer young earthworms hatched than in normal years.
Ehrmann is currently working on recording the population of the animals and, among other things, investigating the influence of climate change on the population. In addition, a long-term study supervised by him on the change in earthworm populations in the southwest forests of Baden-Württemberg as a result of climate change is to be published this year.
Earthworms are extremely important for the quality of the soil, said Nabu agriculture consultant Jochen Goedecke. With their corridors, they aerated the soil and at the same time made it more permeable to water. But higher temperatures and little rain would also have an impact on microorganisms in the earth such as fungi, bacteria and nematodes.
“Every structure, every process has its optimal temperature,” he said. “If it continues to increase, these organisms can no longer be as active.” Processes such as the removal of dead wood and other rotting processes that are important for the environment and the soil would be interrupted or at least not work as well.
Sarah Bluhm, an expert on soil and the environment at the Forestry Research Institute (FVA) in Baden-Württemberg, also believes that climate change and successive hot summers will have an impact on life in the soil and thus on soil quality. How exactly is still unclear. The microorganisms are very diverse, difficult to identify and “the processes in the soil are so complex that it is difficult to say how the system will develop”. Soil animal monitoring is still in its infancy. In general, however, one can say that fungi or bacteria living in the soil become inactive if it is too dry and there is no available water nearby.
Studies in Switzerland, for example, showed that in an experiment where soil in one part of a forest was irrigated and the other part was not, there was less humus in the dry part, she said. The soil-decomposing organisms suffered from climate change. If, in extreme climate conditions, trees die off en masse due to drought, as is already being observed on a small scale, “then we will experience a massive change in the community in the soil and thus in the quality of the soil,” said the biologist.
It is positive that small animals that decompose leaves or dead wood are very resilient and able to compensate for poor conditions for a long time. Overall, their importance cannot be overestimated. “Soil organisms are involved in the storage of carbon, the recycling of nutrients and also have an impact on water quality.”
Ehrmann and Goedecke were also confident that things could soon get better for the little creatures in the ground. “Basically, earthworm populations can recover well,” emphasized Ehrmann. 2003 was also an extremely dry year, said Goedecke – “but in the long term it didn’t matter that much. He emphasized that, in addition to general measures against climate change, people can also help the soil: for example by rotating crops or by Cover floors with plants all year round to protect them from heat.
© dpa-infocom, dpa:230824-99-938985/2
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