Reed bends with the wind along a dike on the Baltic Sea. The sea has an important task here. The seawater lapping against the stems prevents CO2 goes into the air. Draining the peat soil has major consequences. This can be seen on the other side of the dike, where the water no longer comes.
There, beige cows graze in a monotonous grassland. The dry peat – remains of decayed plants – under the hooves of the animals is broken down. As a result, CO2 free. A lot of CO2. The bottom also collapses. The ecosystem has been disrupted: the reed marsh has disappeared. Original inhabitants of fens are not coming back soon, a previous month showed published international research.
A large gray man with a long coat and boots is walking along the dike. Hans Joosten is from Brabant, but has lived and worked here for 25 years in the East German Greifswald, where he is professor of peat science and paleoecology. “I cycle here every morning for a swim. I float in the water while the swallows, swans and sea eagles fly over me,” he says with a big smile.
Joosten received the last month German environmental award. With a team of 70 researchers, he studies the recovery and sustainable use of peat in and outside Europe at the Greifswald Moor Center.
Hundreds of thousands of hectares of peat in Europe have now been flooded again. And also outside Europe, such as in Indonesia. But we’re not there yet, says Joosten. Worldwide, all peat needs to be wet to achieve the climate goals. In Europe, 1 percent of the peat has been rewetted, according to Joosten. “Germany has to flood 50,000 hectares a year to have everything rewetted by 2050. Now they just hit 2,000. In the Netherlands, large parts of Friesland, Overijssel, Utrecht and North and South Holland, among other things, need to be rewetted.” More than 80 percent has been drained for agriculture. That makes it complicated: “The ministries of agriculture only want us to rewet nature areas, but that’s not where the problems lie. They are in agriculture.”
Joosten points to a number of antennas and tubes emerging from the ground on both sides of the dike. Two measuring points. “Thirty years ago a dike was removed here, so that part of the peat is regularly flooded by the sea again.” Three situations arose here. Part of it was already outside the dike. A dewatered part was intensively used grass and arable land, but is now again outside the dike. And part was once wet but is still dry. The perfect place to investigate what drought and rewetting does to the peat and the environment.
Joosten steps onto the peat. Further on, a rectangle of about 10 by 35 meters has been set up, around the measuring equipment. The tubes in the ground are made of plexiglass. “We can put a scanner in it and it can take pictures of the roots.” Mosses grow upwards and die at the bottom. Some of the organic material remains stored in the moist soil. “Like pickles in a jar.” But an important part of the peats does not grow above but below the ground, from the dying roots of plants that take root in older peat. “Those veins grow up by growing down, we don’t fully understand that yet.” This happens in a drier or warmer climate. That is why we also keep track of the temperature of the soil, whether it is raining and which grasses and mosses grow on the peat. It is also investigated how much and which greenhouse gases are released.
Since the 1990s, the University of Greifswald has been collecting information on the effects of rewetting for various projects across Europe. Joosten’s research group threw all this data together for research into biodiversity. Rewetted bogs were compared with nearby bogs that had never been drained.
Ten thousand years
This showed that the biodiversity after rewetting was nowhere comparable to the original peat bogs. “Logical,” says Joosten. The peat was formed in ten thousand years. “Then you shouldn’t expect it to recover in a few decades.”
Fast growers like the bulrush, with the thick brown ‘cigars’, and reed grass often get the upper hand after rewatering. A legacy of agriculture, which allowed many nutrients to enter the soil. Peat is naturally low in nutrients. “Fast growers win because of light competition from species that thrive on poor soil.”
Compare it to a boiled egg, it will never be the way it was again
The peat has also become much more compact and chemically changed due to drainage, so that it retains less water. “You can compare it to a boiled egg, it will never be the way it used to be.” New peat has to be created, a slow process.
Loud chattering. About eight swans fly over. The rewetted peat with a layer of moss on which we walk bounces slightly. It’s autumn, sea asters have just finished blooming. Joosten picks a small plant with thick leaves and puts it in his mouth. What does he eat? “Beef shit.” And he tastes salt. Similar to samphire. The plant has adapted to the wet saline environment. He can tell Joosten by the thick leaves. “A spurrie, I think, spergularia.”
Back on the dike, Joosten explains why rewetting makes sense. The landscape outside the dike may not be as it once was, but the vegetation is already a lot richer than on arable land. For example, the smallest moorhen and white-winged tern are back in other rewetted peat bogs. “They were extinct there for 100 years.”
Soil animals and bacteria
With more patience, the surplus of nutrients will disappear from the peat, allowing more plants and animals to come back. “That is because the cycle is interrupted in living peat bogs,” says Joosten. Normally, nutrients that are absorbed by plants are released again when the plant is dead and are broken down by soil animals and bacteria. In a living peat, plant remains are not completely broken down, but pile up like peat. So the soil is getting poorer. And becomes CO2 fixed. After reclamation, this is released back into the atmosphere. “About 4 percent of the emissions worldwide.”
The bottom of a rewetted peat also stops falling. Dewatered peat bogs sink one centimeter per year. “The western Netherlands has been sinking for a thousand years. The land started 5 meters above sea level and is now 5 meters below. Some areas can sink another 20 meters.”
Also read: Methane is an erratic greenhouse gas from cows, ditches and rubbish dumps
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