Peatlands are landscapes characterised by permanent water levels. A distinction is made between raised bogs and fens. In raised bogs, the amount of precipitation is higher than the water loss through evaporation, this leads to the accumulation of water in the area. The vegetation is mainly formed by peat mosses. The water-induced lack of oxygen results in a higher production of plant matter than can be decomposed and a growing peat layer is formed. Fens are depressions in which nutrient-rich water, for example groundwater, collects. Due to the high nutrient content, fens form a particularly species-rich habitat with diverse vegetation and animal populations.
Peatlands have various important ecological functions. Besides forming a unique ecosystem with high biodiversity, peatlands act primarily as water and carbon reservoirs. Like a sponge, peatlands can store water during rainy periods and then gradually release the water into the environment. This water regulation of peatlands can prevent flooding and catastrophic floods. The absorption of water also results in nutrients and pollutants being filtered out of the water, thus ensuring water quality. The filtered water from the peatlands is released into the surrounding aquifers, lakes, streams and rivers.
In addition to water storage, the ability to store large amounts of carbon is an important property of peatlands. Due to the water level and the resulting lack of oxygen, decomposition processes of organic material are very slow. The partially decomposed material is deposited and forms carbonaceous peat. Peatlands store between 150 and 250 million tonnes of CO2 per year. And although peatlands make up only 3% of the world's land area, they store twice as much CO2 as forests, which form a much larger proportion of the land area at 30%.
When peatlands are drained, they are, for example, drained by means of drainage ditches in order to be able to use the area for other purposes. However, drainage has various negative effects. Firstly, the soil loses structure and becomes sandy (fine humus). In addition, the dried peat in a bog is highly flammable and can also start large and hardly extinguishable fires underground. In addition, the bog soil loses volume through drainage. The soil of a drained bog can sink up to 3cm per year. As a result, the constant drainage effort and the associated costs continue to increase. The worst consequence of peatland drainage, however, is that as the water level falls, the peat mineralises and releases large amounts of CO2 and nitrous oxide, whereby nitrous oxide has an effect that is about 300 times more harmful to the climate than CO2. The former carbon sink of peatland is now becoming a source of greenhouse gas and thus contributing to global warming. Drained, burning and otherwise used peatlands emit 3000 million tonnes of CO2 annually, which corresponds to 10% of global emissions from fossil fuels. Although only 0.4% of the world's peatland area is drained, the amount of CO2 in the atmosphere has increased by 5%. In Germany alone, 5.4% of the nationwide emissions are also caused by drained peatlands. The renaturation of peatlands is therefore an important and unavoidable aspect of combating the climate crisis.
The renaturation of peatlands can transform them from greenhouse gas sources back into carbon sinks. However, for this function to be fulfilled, several steps must be followed and the process takes time. The first step in restoring a peatland is to restore the water level. To do this, dams and pumps must be removed and drainage ditches dammed. In the case of peat extraction areas and raised bogs, the remaining peat is levelled and rainwater retention basins are built to allow the water to accumulate. Once the water level is in place, invasive vegetation must be removed. Trees and other plants that do not belong in the bog otherwise consume too much water and increase evaporation from the area. To keep the water level high, this vegetation must therefore be removed and in the next step the original bog vegetation must be reintroduced. Typical bog vegetation includes, for example, peat mosses. Finally, extensive paludiculture can be introduced on the renaturalised area. Paludiculture refers to the use of land on wet soil by, for example, water-tolerant livestock farming, lighter agricultural machinery and crops growing on wet soil.
The cost of rewetting peatlands is highly site-dependent. However, a German study has determined costs of 10 - 15€ per tonne of CO2 for rewetting. With subsequent land use through paludiculture, this price is even lower. This makes the rewetting of peatlands significantly cheaper than other land-use-based measures to avoid greenhouse gas emissions, such as the production of coppice forest with short rotation and the production of raw materials for biomethane production.
Peat soils in Germany contribute significantly to greenhouse gas emissions. Nationwide, about 44 million tonnes of CO2 equivalents are released from drained, German peat soils. In Mecklenburg-Vorpommern, peat soils are responsible for over 36% of the state's emissions!
The German government's national peatland protection strategy aims to reduce CO2 emissions from peatland soils by five million CO2 equivalents by 2030. This is to be implemented primarily through various funding programmes. There are already various projects and funds at federal and state level, and also at European level, which finance and promote peatland protection projects.