SZ series: Man and forest, episode 6 – Climate protection in the Käferwald – Bavaria

Stefan Müller-Kroehling is a man who can get excited. He loves the ground beetles, especially those ground beetles that run through the Bavarian moors. That’s why he brought his doctoral thesis with him to the appointment in the undergrowth in addition to various research tools, on which he wrote for ten years on the side: “Ground beetles as characteristic species in Bavaria’s forests” is the name of the work that he carries in a shoulder bag. Where other people only see undergrowth and would at best complain about full running shoes, Müller-Kroehling recognizes the big picture in the small things. He is in his element there.

So it is on this cloudy morning south of Grießenbach, a town near Wörth on the Isar. Müller-Kroehling is progressing towards the research area – a piece of forest that looks rather unspectacular, apart from the fact that the Bavarian mosquitoes are holding their state assembly here. The traffic noise of the A 92 blows over from the south, a buzzard screams. No area for tree huggers. Just a forest. But from the point of view of the qualified forester Müller-Kroehling a very special one. He takes out his boring stick and rams it into the ground: a crumbly layer of peat appears in the drill core, too dry, but still two meters thick. It is of interest to researchers like Müller-Kroehling and, more recently, the state government.

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Because here in the Grießenbacher Moos a fen is spreading, i.e. a wetland in which the groundwater collects. Over time, a layer of peat grows upwards out of the dead plants, millimeter by millimeter – after all, a raised bog is created that stores rain like a sponge. The process only works like this if the system remains undisturbed.

But peat has not only been used as fuel in Bavaria since the 19th century, even locomotives were fired with it in order to conserve the scarce wood supplies. When heating material was particularly scarce after the First World War, Bavaria passed the Peat Management Act and the Wasteland Act. As a result, peat factories were built on state-owned land in the 1920s, which caused great destruction by the end of the century – most recently for the extraction of garden peat, which is now being carted in from Eastern Europe. In Bavaria, peat mining has been stopped with a few exceptions. Here one tries to correct the mistakes from the past.

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This is also the case in Grießenbacher Moos, a relic from the time when the Isar still meandered freely through the valley before it was straightened like almost all other rivers in the 19th century. Later the farmers dug drainage ditches through the “unland”, as such areas were called; in the 1980s the motorway was added – the water table continued to sink, and the drying bogs turned from carbon dioxide stores to greenhouse gas emitters. Müller-Kroehling does the math: peat soils cover three percent of the area of ​​Bavaria, but they are responsible for six percent of CO2 emissions. Nitrous oxide gets into the atmosphere, especially where intensive agriculture is carried out on it.

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Not only Müller-Kroehling would like to reverse that. In recent years, researchers around the world have discovered the value of moors for climate protection. Whereby the Bavarian moorland with its 2115 square kilometers look rather puny. The Wasyugan Bog in Siberia alone would cover three quarters of the Free State with its 53,000 square kilometers. It is impossible to imagine what happens when such a surface dries out.

So what should you do? In principle it is very simple – also in the Grießenbacher Moos: “The point here is to raise the groundwater level without creating any discomfort,” is how Müller-Kroehling sums up the project. In order for the moor to store carbon dioxide again, it only needs to be watered. But the word “Affected” indicates the problem: A large part of the fens is covered by commercial forests on the one hand, and privately owned, on the other, as here in Grießenbach. If the trenches were completely filled in or dams built, spruces, for example, would be dead after a few months. A horror for forest owners, whose capital investments are already suffering from climate change.

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This is where Müller-Kroehling and his employer, the State Institute for Forestry and Forestry in Weihenstephan, come into play. The state authority with its 180 employees has been researching the forest ecosystem and everything related to it for 140 years – the tasks range from forest technology and hunting to advising private forest owners. Müller-Kroehling is the specialist for Bavaria’s forest bogs, and as such, he and his team in Grießenbach have been investigating how the conservation of bogs and forest management can be reconciled on an area of ​​60 hectares since June 2021. “That will be the blueprint for protecting the bog forests,” he hopes. Müller-Kroehling owes the fact that he can work here to the forest owner Christoph Freiherr von Grießenbeck, a “citizen of the world”, as he says, who also cares about the forest in which the ash trees are dying away in rows. Specifically, it deals with the question of what groundwater level the trees can tolerate and where the best compromise between climate protection and wood yield is. “You cannot rewet the moor as it used to be,” says Müller-Kroehling. If the peat layer is to be preserved, the water must be about 50 centimeters below the surface. He thinks that is feasible, in which way, exactly, they still have to find out. And Grießenbeck would also have to agree after the inventory has been completed. With the exception of the ash trees, his forest is still in relatively good shape. He started to rebuild it decades ago. Today black alder, peat birch and Scandinavian aspen, which are also in demand as timber, grow upwards. The harvest will of course be more difficult when the fen has been renatured again. There must be state support for this, says Müller-Kroehling, after all, the forest owner provides a service in the service of the common good.

And then there are the bugs. Müller-Kroehling calls them “little field workers”. There are 500 different species of ground beetle in Bavaria, all of them have very specific habitats. Anyone who wants to record the condition of a bog can measure the pH value. But it can also catch beetles and determine: “Each species tells me something.” Such a Carabus Granulatus would now say, for example, that this is a typical fen because it occurs in abundance. Unfortunately, the green and gold Carabus Granulatus is uncooperative, it is hiding on this day.

Instead, Müller-Kroehling comes across Leistus rufomarginatus, the red-rimmed beard in the dead wood. It can fly and likes warmth, which is why it is spreading more and more in Bavaria. The other beetle that goes into the sieve is a common shoulder walker, one of the most common ground beetles in the woods. The two specimens show an expert like Müller-Kroehling: The condition of the Grießenbacher Moos is not yet that great, because the species are atypical for intact moors. They mark the current state.

But that should change, not only here, but also elsewhere. “Time is of the essence, we want to present results,” says Müller-Kroehling. He hopes the time will come next spring. Then an almost completely destroyed landscape could revive in Bavaria – in the service of climate protection.