Research for climate protection: more wet! The renaturation of dry peatlands would save millions of tons of greenhouse gases

The song of the skylark is a small miracle.

Research for climate protection: more wet! The renaturation of dry peatlands would save millions of tons of greenhouse gases

The song of the skylark is a small miracle. It seems to sound straight out of heaven. Often a hectic "prriit-prriit-prriit-prriit-prriit" can be heard - but not a bird to be seen far and wide. When singing, the male flutters up to 200 meters and thus makes himself invisible to us. No one knows where the little bird gets its air from so that it can cheer and soar at the same time. Anything to seduce a female.

Also over the Karrendorfer Wiesen near Greifswald an invisible lark man is singing from above. Good for ornithologists, because the skylark is considered endangered. For peat researchers, however, this is a clear sign that something is wrong here.

"When I hear a skylark, I know: the moor is too dry," says Franziska Tanneberger from the University of Greifswald. The landscape ecologist runs the Greifswald Moor Center with a lot of passion and is considered one of the leading experts in the country. She talks animatedly, shows and explains while she trudges in rubber boots over the dyke that still separates part of the Karrendorfer Wiesen from the Greifswalder Bodden. To the left of the dike is a wide expanse of grass that to the uninitiated - and probably to skylarks too - looks like an ordinary cow pasture. The birds look for dry meadow hollows for their nests. But that's exactly what shouldn't exist here in the Karrendorfer Wiesen. Because the meadows are a moor.

To be more precise, a coastal floodplain on a promontory in the Greifswalder Bodden, more than 360 hectares in size. Several times a year, the Baltic Sea floods part of the meadows, moistens and salts the soil, leaving pools and puddles behind. But the sea only catches the part that is on the outside. In front of the dike. There the moor exists in its wet original form: there are no peat mosses here on the Baltic Sea, but there are waving forests of reeds taller than a man. Bog grasses such as sedges and rushes sprout like sparse stubble from ponds and puddles.

Behind the dyke, on the other hand, it is hard to guess what you are dealing with: "Here, water is still being pumped into the Bodden, and typical moor plants have not been growing here for a long time, but various sweet grasses that were sown as pasture for the cattle", explains Franziska Tanneberger and crosses a drainage ditch next to a white and blue pump house. For centuries, the Karrendorf meadows were kept dry with the help of ditches and later also pumps in order to use them as cattle pasture. From 1850 a dyke was built around the flat headland to stop the flooding from the Baltic Sea. But beneath the turf, the meadows remained a bog: their soil consists mainly of peat, of dead plant biomass that has only partially decomposed. Here it is mainly the mortal remains of sedges, rushes, reeds and cattails.

From today's perspective, the black-brown peat is probably the most valuable thing that moors have to offer. At least as long as you leave it wet and otherwise alone. While peatland protection used to be primarily about preserving rare species, such as sundews, snipes or the aquatic warbler, which is now practically extinct and on which Franziska Tanneberger wrote her doctorate years ago, researchers today tend to see wetlands as powerful climate machines. Because the climate potential of moors, whether in Europe, Indonesia, Siberia or in the huge Congo Basin, is enormous: According to the current "Mooratlas", which is published by the Heinrich Böll Foundation and the Greifswald Moor, among others, they cover only three percent of the earth Center is published. But in this area, moors bind almost twice as much carbon as the much larger forests on earth. In Germany alone, 1.3 billion tons of carbon are stored in the peat of the moors, worldwide it is said to be 600 billion tons.

Mighty layers of peat grew over thousands of years where water accumulated underground: where it rained a lot, as on the edge of the Alps, peat moss soaked up and raised bogs developed. In Mecklenburg-Western Pomerania or Schleswig-Holstein, fens formed in the damp lowlands, where grasses such as sedges, rushes, reeds or cattails stand in the water. As long as they are alive, bog plants absorb large amounts of carbon dioxide from the air and store it in their stems, leaves and roots. What then withers and dies falls into the water. It rests there, hermetically sealed. "My colleague Hans Joosten once coined the analogy of the pickle jar," says Franziska Tanneberger. "As long as the cucumbers are in the water and the lid is on, they can sit in the pantry for years. But as soon as you open the lid and drain the water, the cucumbers will rot in the air in a short time,” explains Tanneberger.

This pickle-jar effect has made the moors popular as climate protectors - and has meanwhile given Tanneberger more appointments in the Greifswald Moor Center than her calendar can hold: delegations from the Bundestag want to find out more about moors and the climate, foreign scientists want to learn how to use moor fields again can get wet, farmers and local politicians discuss with her how to reconcile renaturation, climate protection and agriculture. Because Germany has had a moor problem so far: there are 1.28 million hectares of moor soil in this country. But 98 percent of them have the lid off, so to speak. You are constantly dehydrated. Pumping stations extract the water from them, ditches divert it. Such drained moors are mostly used as cow pastures, potato or corn fields. Large parts of Hamburg and Berlin were also built on drained moors.

These bogs without a water cover are a huge problem because the carbon in the dried peat comes into contact with oxygen and decomposes extremely quickly. Especially carbon dioxide. In Germany alone, drained peat soils emit greenhouse gases in the order of around 50 million tons of CO2 every year. This corresponds to one third of the emissions from German road traffic. Tanneberger criticizes that bogs are still too generally regarded as sinks for CO2. “But in Germany, they should honestly be counted among the sources at the moment – ​​just like traffic, power plants or industry.” However, it doesn’t have to stay that way: “The interesting thing about dry moors is that you can stop their emissions very quickly and easily. You have to stop the drainage, roughly speaking: turn off the pumps and level dikes and ditches. Then a moor quickly fills up again by itself. And with that, we not only set peatland emissions to zero, but are even moving in a positive direction again and can bind CO2.”

"Moor must wet!" is therefore written on a small sticker that is stuck to her office door at the Institute of Botany at the University of Greifswald. Because Tanneberger is not only a moor researcher, but has now become something of a moor ambassador, receiving politicians and journalists, meeting nature conservationists and officials. Her book with the simple title “Das Moor” (dtv, 24 euros) has just been published. It interweaves her research with the plea to finally protect the last moors in the world - and with her own story. Growing up in East Berlin, she often spent her summer holidays as a child between moor meadows and the beaches on the island of Usedom. At 17, still in the days of the GDR, she traveled to Russian Novosibirsk for the first time and fell in love with the vast plains of Siberia. During her studies, she kept coming back, for example to the Wasjugan Moor, the largest primeval moor in the world, twice the size of Belgium. She once had doubts about whether she would leave it alive after a helicopter pilot had forgotten her research group in the middle of the wilderness.

Today it is above all the dry moors that Tanneberger fights for, moors that lie invisible, as if sleeping, in the landscape, hidden under turf or corn plants. Tanneberger would like to transform them back into their original wet form. Just like others have done with the Karrendorfer Wiesen, a success story of German moorland rewetting. There were hardly any conflicts there, explains the ecologist, “because some of the land belonged to the state anyway and at some point the wet meadows were no longer attractive for agriculture. The dyke was in bad condition, partly already broken. So the question arose: shouldn't we just give the meadows back to nature?"

Researchers at the University of Greifswald have been campaigning for this since the 1990s. In the end, six kilometers of dikes around the headland were dredged away. In the meantime, only a short wall protects the village of Groß Karrendorf from the sea. The largest part of the area is moor again and belongs to the Succow Foundation for the Protection of Nature, set up by moor ecologist Michael Succow. The Karrendorfer Wiesen have long been a hotspot for ornithologists looking for rarities such as phalanges and avocets. Nature tourism is booming.

Elsewhere, conflicts are hampering the revitalization of the drained areas. Usually the land belongs to someone who makes a living from it. In some bogs, peat is still cut for potting soil, even if the permits for this expire in a few years. Most drained peat soils are used for agriculture. And not every farmer wants to see their property underwater. “Moor and rewetting can only be managed cooperatively. Science, authorities, farmers and nature conservationists have to talk to each other - also about value creation: How can money be made with wet moor?" says Tanneberger.

So-called paludiculture offers a solution – the commercial cultivation of typical moor plants on wet soil, ideally where this soil is already being used for agriculture. Frugal water buffalo can be grazed on wet moorland and mozzarella can be made from the milk. Lingonberries and cranberries can be cultivated in the bog, the first companies are experimenting with sundew for cough medicines or are brewing beer with the aroma of bog bilberry again, as was common in Scandinavia in the past.

Wet paludiculture would also promote climate protection: One hectare of dry moorland emits various gases with a greenhouse effect equivalent to 40 tons of CO2 per year - a paludiculture only 0 to a maximum of 8 tons. The greatest hopes are currently pinned on cultivated bog grasses: "Sedges, for example, have great potential," explains Franziska Tanneberger. They can be mowed and then processed into compostable packaging, for example. In future, reeds for thatched roofs should increasingly be planted in the domestic wet bog instead of being imported from China and Eastern Europe, as is currently the case. Fibers from cattail plants are suitable for construction and insulation boards. A company in East Germany is currently building the first tiny houses from Paludi materials: built and insulated with reed, cattail and alder wood.

In order to understand the conditions under which moor plants thrive, a kind of moor of the future is growing in the courtyard of the Institute of Botany at the University of Greifswald. In 108 black plastic vats.

There is a cattail plant in each pot, the plants are weighed regularly and watered automatically via hoses, some are also fertilized. Transparent tubes lead into the peat balls. A scanner with a camera can be inserted there to photograph the roots of the plants and use the images to calculate how diligently the plants have formed biomass and peat and bound carbon. “So far, ironically, most of the research has been on drained peatlands. We know the yields of potatoes or corn on dry peat soil. But we know comparatively little about the wet moors and their typical plants,” says Tanneberger, pulling a fibrous, straw-yellow ball out of a bag: They are dried cattail roots that are surprisingly soft to the touch, almost like wool or felt.

“Bulrushes are extremely productive plants. Amazingly, we have found that even mowing is not a problem. Most of the carbon is namely fixed in the roots. So we can harvest at the top and at the same time protect the climate underground. That’s why paludiculture is really a well-rounded thing.”

What annoys the researcher, on the other hand, are "moor potatoes" or "moor carrots", which are still offered at weekly markets and in organic shops, sometimes even as supposedly sustainably produced vegetables: "Unfortunately, that's a big mistake. Bog carrots and bog potatoes are definitely outdated. Cultivation only works on heavily drained areas, which release massive amounts of greenhouse gases. We shouldn't continue something like this for reasons of climate protection."