Drought leaves Bavarian forests short of mushrooms

After a prolonged dry spell, few mushrooms are appearing in many Bavarian forests, BR reported. Recent rainfall has done little to change the situation, raising concerns not only for mushroom pickers but also for the wider forest ecosystem.

In many places, the forest floor around the Ammersee is currently covered in dust. Christoph Hahn, a mycologist and chairman of the Bavarian Mycological Society, said the lack of mushrooms was therefore unsurprising. At this time of year, he would normally expect to find species such as brittlegills and broad-leaved bonnet mushrooms growing on dead wood.

Although it has rained recently, the moisture has not yet reached deeper layers of the soil, Hahn said. The ground remains completely dry and hard, making the rainfall little more than a drop on a hot stone for now.

The drought affects more than the visible fruiting bodies of mushrooms. Underground, extensive fungal networks known as mycelia form an important part of the ecosystem. Many fungi live in symbiosis with trees, helping them absorb water and minerals through their roots in exchange for nutrients.

Fungi themselves also need sufficient moisture, particularly to produce fruiting bodies. A dried-out mushroom from the previous year was the only example Hahn found on the forest floor. The mycelium may still be present in the tree stump, he said, but may currently lack the energy to produce new growth.

The absence of mushrooms does not therefore necessarily mean they have disappeared. The fungal network may still survive in soil or wood. Whether it can withstand the drought and later produce fruiting bodies will depend on how long and how severe the water shortage remains.

It is difficult to predict whether the mushroom season will still arrive in some regions this year. The outcome will depend largely on how severely the mycelia have been damaged. Hahn expects a patchwork pattern: mushrooms could still grow in soils that retained water, while they may fail completely in more heavily affected areas.

Short periods of rain may not be enough after a long drought. Many fungi can resume their development only once sufficient water has entered the soil and remains available for a longer period. If that happens, conditions can change in some places within just a few days.

Hahn is more concerned about the long-term consequences. He said Mediterranean mushroom species were already moving into the region and could fill gaps left by native species. But if dry periods continue to become more frequent, nature may not be able to adapt quickly enough, potentially accelerating species loss.

The effects would extend beyond individual mushroom species. Fungi decompose dead wood, return nutrients to the natural cycle and maintain close connections with trees. Changes in fungal communities could therefore affect the entire balance of the forest.

Hahn said forests needed to be rapidly restructured, preferably with native tree species better suited to the changing conditions. He opposed planting large areas with non-native trees chosen for their resistance to drought, warning that this could disrupt the interaction between fungi, bacteria, microorganisms and trees in the soil.