Quedlinburg, Dusseldorf and Freiburg are places where you can still find ancient oaks, rare beech groves and dark fir forests. However, according to foresters' forecasts, these natural landscapes may change in the near future. "You might like to imagine the forest as it was when you were a child, but now the forest is changing," says Henrik Hartmann, head of the Forest Protection Institute in Quedlinburg.
Trees are facing the consequences of climate change: heat waves, prolonged droughts and storms weaken them. In recent years, extreme weather conditions have damaged forests, and many pests such as insects and fungi have taken advantage of the rising temperatures, which accelerate the conversion of forests, says Ralf Peterkord, a forestry expert at the North Rhine-Westphalia Ministry of Forestry.
This is especially noticeable in fir trees. For centuries, forestry developed using fast-growing fir trees, which led to the formation of pure stands. However, these plantations have become a favorite habitat for the larvae of book printing beetles, which have significantly damaged spruce forests, especially in regions such as the Harz. Spruce trees have the highest mortality rate among tree species.
Even high-altitude areas previously considered safe for spruce trees are now subject to bark beetle attacks. "Even at an altitude of 1,000 to 1,500 meters, the temperature is sufficient for the reproduction of the book printer," explains Markus Kautz of the Forestry Research Institute of Baden-Württemberg. As a result, pure spruce forests can remain only in the Alps.
Oaks were also affected. During the last survey, almost half of the examined oaks showed significant thinning of the crown, which attracted the attention of the oak beetle. This pest can cause serious damage to oak trees, especially if the trees are already weakened by other factors such as flooding.
Beech trees, which once dominated German forests, are also facing problems. Currently, beech trees make up only 16% of the total forest area, and they are often stressed by rising temperatures. "At the end of the century, beech trees may not reach a height of 30-40 meters, and the forests will become thinner," predicts Hartmann.
Beech complex disease, which occurs after heat or drought, is also a threat. This disease begins with cracks in the trunk and secretion of mucus, and later leads to bark rot and the spread of fungi, such as beech bark beetle. "We don't know for sure what's going on, maybe it has something to do with bacterial contamination," says Hartmann.
Ash and maple also face problems. Maple is affected by the fungus Cryptostroma corticale, which causes peeling of the bark and the formation of black dust. Ash, in turn, suffers from the fungus Hymenoscyphus pseudoalbidus, which kills trees. Researchers from the Leibniz Center for Agricultural Landscape Research have discovered bacteria that can suppress the growth of fungus on healthy ash trees, but this issue still needs further study.
"Trees are able to effectively defend themselves against insects and fungal invasions," says Peterkord. . However, the balance between trees and other organisms is often disturbed. If the trees are not strong enough to create protection, this leads to problems.
Today, foresters are increasingly inclined to create mixed forests instead of pure plantations. "We have to consider species from other regions as potentially local in the future," says Hartmann. Research suggests that future forests may include trees from other regions adapted to new climates. The so-called "assisted migration" involves the selection of trees from remote regions that are best adapted to the future climate.
