Peatland Must Be Wet

Abstract

Peatlands contain more carbon than the entire global forest biomass, but their importance has long been overlooked. Currently drained peatlands (on 0.4% of the world’s land area) cause greenhouse gas emissions that amount to almost 5% of the worldwide total. Most of these emissions come from lands used for drainage-based agriculture and forestry. To meet the climate goals of the Paris Agreement, all intact peatlands must remain wet and all already drained peatlands (500,000 km²) must be rewetted. Any peatland use should only take place under wet conditions.

The greatest challenge for rewetting lies with peatlands in intensive agricultural use. These lands urgently need alternative (wet) production methods (paludiculture) to allow productive use while avoiding the environmental harm from conventional drainage-based peatland use. This requires cross-sectoral national peatland protection strategies with measures to strengthen structures and promote innovation. The massive implementation on the ground, however, is best left to the self-directed momentum of enterprises and markets steered by climate protection rewards (“carbon credits”) as a transitional strategy to facilitate a rapid start-up of peatland rewetting. In this way, companies can compete with drainage-based peatland use until paludiculture is technically fully mature and economically self-sustaining.

Peatlands are in everyone’s mouth these days. This is quite literally true, because—as few people know—nowadays nearly all fruits and vegetables ending up on our plates have at some point grown on peat, as have most of the ornamental plants or shrubs we plant in our gardens. Frequently mentioned are the so-called ecosystem services of peatlands, especially their potential to mitigate climate change. This chapter presents an overview of the relevant facts, challenges, and solutions.

What Peatlands Are and What Makes Them So Special

Intact (natural, living, growing) peatlands are ecosystems without a closed cycling of matter. Due to permanent water saturation of the substrate, the remains of dead plants decompose more slowly than new plant material is produced. Over time these remains—in various stages of decomposition—accumulate as thick layers of carbon-rich organic material, which we call “peat”. Worldwide, peatlands—by which we conventionally understand areas covered with at least 30 cm of peat—cover about 4 million km² or 3% of the Earth’s land area, almost as much as the European Union. Because of the enormous carbon density of peat, a threshold value of 10 cm (instead of 30) would be better from a climate perspective and would substantially “increase” the global peatland area.

Peatlands exist in 169 of the UN’s 193 member states; on the European continent they cover an area of about 600,000 km², 12,800 of these in Germany (Tanneberger et al., 2017a, b). Peatlands are predominant in three humid climate zones: in the northern subarctic/boreal zones, in the equatorial tropics, and in the subantarctic regions (Fig. 1, Joosten, 2016). In the latter zone, at the southern end of the inhabited world, peatlands are insignificant in terms of area because there is hardly any land at those latitudes. Relatively speaking, however, they loom large there; Tierra del Fuego, the Falkland Islands, Tasmania, and the South Island of New Zealand all have substantial peatland cover. As peatlands exist all over the world, it is inevitable that, despite all their commonalities, they differ widely in their biodiversity.

Fig. 1

Known occurrences of peatlands, as of 2021. In the red-brown colored areas, peatlands occupy more than 50% of the mapping unit, in the light-brown colored areas 20–50% (Greifswald Mire Centre, 2022)

In the long term, growing peatlands cool the climate because they act as CO₂ sinks. But their direct, short-term importance should not be overestimated. On the one hand, the net carbon sequestration due to peat formation in the still growing peatlands (about 100 million metric tons of carbon per year) compensates for only 1% of anthropogenic CO₂ emissions. On the other hand, living peatlands also produce and emit methane (CH₄) due to the prevailing oxygen-free conditions (which enable peat formation and preservation in the first place). Worldwide CH₄ emissions from peatlands are “only” 30 million metric tons per year; but because methane is a much more potent greenhouse gas (GHG), the positive climate effect of CO₂ sequestration is arithmetically more than offset by the methane emissions. Seen from a short term perspective, living peatlands are therefore, on the whole, no help against climate change. In the longer term, however, they have a cooling effect because methane oxidizes quickly in the atmosphere, thus losing its strong climate effect. As a result, the permanent methane production of living peatlands does not lead to a permanently increasing concentration of methane in the atmosphere, while the ongoing sink effect continuously reduces the CO₂ concentration in the atmosphere. In this way, peatlands have cooled the global climate over the last 10,000 years by about 0.6 °C (Frolking & Roulet, 2007; Joosten et al., 2016; Günther et al., 2020).

Typical Features of Peatlands

• high content of organic matter and carbon in the soil;

• permanent water saturation and a slow but continuous rise of the groundwater level as well as the surface elevation;

• relative lack of nutrients and often high acidity;

• a cooler and more humid mesoclimate compared to the surrounding area;

• occurrence of harmful organic substances, toxic, chemically reduced elements, and black water.

All these factors shape the habitats of the often very specialized biota typical of peatlands.

Furthermore, peatlands are characterized by their capacity for:

• long-term carbon sequestration and storage;

• water purification and retention and regulation of run-off;

• accumulation and preservation of palaeoecological information and archaeological artefacts.

The sophisticated interplay of plants, peat, and water enables the long-term development of self-regulation and self-organization, making peatlands resistant, long-lasting ecosystems with often fascinating surface structures and unique ecosystem biodiversity (Convention on Wetlands, 2021a; Couwenberg et al., 2022).

Of much greater, direct climatic importance is the role of peatlands in storing carbon—i.e. as possible sources of CO₂. Compared to other ecosystems, peatlands contain a disproportionately large amount of carbon: in the boreal zone on average seven times as much per unit area, in the tropics ten times as much as ecosystems growing on mineral soils. And although they cover only 3% of the world’s land, peatlands store 600 billion metric tons of carbon, almost twice as much as the biomass of all the world’s forests, which account for about one third of the land area (see also Chapter “Humus Enrichment of Soils”) (Joosten & Couwenberg, 2008; Joosten et al., 2016; Kirpotin et al., 2021; Temmink et al., 2022).

The importance of peatlands in terms of their biodiversity and ecosystem services has long been overlooked. Richard Lindsay called this at the 6th Conference of the Parties to the Ramsar Convention on Wetlands in Brisbane in 1996 “the Cinderella Syndrome” (Lindsay, 1996). It took until 2002 for the Convention to recognize the importance of peatlands and to explicitly call for their protection and restoration (Barthelmes et al., 2015). The Convention on Biological Diversity (CBD) has likewise thus far barely taken notice of peatland biodiversity, even though, due to their special peat-forming properties, peatlands are home to many species that are found nowhere else and thereby contribute disproportionately to regional biodiversity. Furthermore, as already mentioned, peatlands possess an ecosystem biodiversity—largely independent of genetic diversity—with a great richness of peatland forms and surface patterns (Joosten et al., 2017; UNEP, 2022). Instead of appreciating this characteristic, international decision-making processes often merge peatlands with other wetlands that lack a peat layer and have completely different functional characteristics (Minayeva et al., 2017).

For a long time, the Climate Convention (UNFCCC) treated peatlands in a similar manner as the Ramsar and Biodiversity Conventions. It was only in 2012 that it recognized the importance of peatlands for climate protection and included the rewetting of peatlands as an eligible measure in the Kyoto Protocol. At the same time, within the framework of the REDD+ mechanism (Reducing Emissions from Deforestation and Forest Degradation), the peat soils of the swamp forests were recognized as an inseparable part of “forest carbon” (Joosten, 2011).

The Condition of Peatlands—Globally, in Europe, and in Germany

In relative terms, the world’s peatlands seem to be doing not so badly: Their area is currently larger than it has been in most of the last 100,000 years. The global loss of intact peatlands amounts to about 15%, while a third of all former forest areas on earth have disappeared (Ritchie, 2021). Globally, peatland area is decreasing by 0.1% per year versus 0.3% for tropical primary forests; the global peat volume is also being reduced by 0.1% annually versus 2% for crude oil reserves (Joosten & Clarke, 2002; World Resources Institute, 2022; Worldometer, 2023).

The global peatland problem has two aspects. (1) Peatland losses are concentrated in regions where the climate is suitable for agriculture, especially arable farming. As populations keep growing, and warming increases, the pressures to exploit these peatlands will continue to rise. (2) Peatland degradation immediately leads to enormous impacts on the climate because very large amounts of rapidly releasable carbon are present in small areas.

The State of the Peatlands

According to the most recent figures, as mentioned already, about 4 million km² of peatlands are currently inventoried. But unfortunately, the inventory is inadequate; so the figures in circulation (including ours) are not as precise as they appear and should rather be regarded as suggesting an order of magnitude. In fact, so little is known about some areas that huge “new” peatlands are still being discovered, in large parts of Africa, for example, and in South and Central America (Kirpotin et al., 2021; Dargie et al., 2017; Draper et al., 2014; Elshehawi et al., 2019; Peters & Tegetmeyer, 2019).

Worldwide, about 85% of today’s peatlands are (still) in a largely natural state; in parts of Canada, Alaska, and Siberia, they can still be found over very large areas (UNEP, 2022). However, over an area of 500,000 km², peatlands have been disturbed to such an extent that peat no longer forms; on the contrary, the organic matter that accumulated over thousands of years is gradually disappearing (Fig. 2). In short, pristine peatlands are concentrated in the (sub)arctic and boreal zones, while drained and degraded peatlands are found in the temperate and increasingly also in the (sub)tropical climate zones.

Fig. 2

Current global proportional distribution of peatlands (with over 30 cm of peat) and peatland losses per continent (in km²) relative to the maximum extent reached during the Holocene. (After Joosten, 2009 and Joosten, unpublished)

Europe’s long cultural history, high population density, and climatic suitability for agriculture have made it the continent with the globally largest peatland losses. So much peat has disappeared from 20% of the original peatland area that they no longer qualify as peatlands (Fig. 2), more than half no longer accumulates peat, outside Russia even two thirds of the peatlands are “dead”, in many European countries more than 90%.

Every year, a further 5000 km² (about 0.1%) of natural peatlands are destroyed worldwide by human activities. This is a fast rate of destruction, considering that over the last 10,000 years peatlands have expanded ten times more slowly. The main causes of peatland loss were and are drainage for agriculture and forestry, peat extraction (formerly for energy production, nowadays mainly for horticultural substrates), and the expansion of built infrastructure, including reservoirs, or urbanization (Joosten, 2016).

Climate Impact of Drained Peatlands

When peatlands are drained, penetration of oxygen into the peat soil leads to a steady depletion of the peat body. The accumulated organic matter oxidizes and disappears into the atmosphere in the form of the GHGs carbon dioxide (CO₂) and nitrous oxide (N₂O). These emissions correlate strongly with the average level of the groundwater table in the peatlands. In Central Europe, each lowering by 10 cm leads to additional emissions of 5 metric tons of CO₂e per hectare and year; in the tropics the figure can be as high as 9 metric tons (Jurasinski et al., 2016; Hooijer et al., 2006; Couwenberg et al. 2010; Carlson et al., 2015). The concrete consequences of this are, exemplarily, as follows:

An arable field on drained peatland soil in Germany emits 37 metric tons of CO₂e per hectare per year—the same amount of GHGs that a medium-sized car with a gasoline engine releases when it is driven 185,000 km per year (over four times around the Earth) (Joosten, 2017).

Effusively advertised peatland potatoes, carrots, and maize should thus be labelled and treated as fossil, not as renewable raw materials, crops, and fuels because more carbon disappears from the peat soil where they grow than they fix in their biomass.

Each liter of milk from a cow fed mainly from peatland grass- or farmland is almost as CO₂-intensive as burning 2 L of gasoline; the CO₂ footprint of 1 kg of peatland cheese is 45 kg of CO₂e, that of a kilogram of peatland butter almost 100 kg of CO₂e (Chemnitz & Becheva, 2021).

“Bioenergy” produced from plants grown on drained peatlands (such as maize, the Chinese reed Miscanthus, sugar cane, palm oil, or wood) releases more fossil carbon per unit of energy produced than fossil fuels do. “Biogas” from “peatland maize” is eight times more harmful to the climate than burning lignite (Couwenberg, 2007).

One liter of edible palm oil produced on peatland emits 15 kg of CO₂ (Hiraishi et al., 2014; Couwenberg & Hooijer, 2013; Schleicher et al., 2019), six times as much as burning 1 L of gasoline. With the CO₂ that one hectare of palm oil plantation on peatland produces each year, one could fly 50 times per year, i.e. nearly once a week, from Berlin to Jakarta and back, economy class (Hiraischi et al., 2014).

The Climate Impact of Degraded Peatlands

While natural peatlands have been cooling the climate for over 10,000 years, drained and degraded peatlands are significant sources of GHGs and thus contribute to global warming. These GHGs are produced mainly by the microbial oxidation of organic matter once air enters the formerly water-saturated peat.

The drier conditions also increase the risk of fires. In addition to GHG emissions, smoldering peat fires cause haze that can extend far beyond its region of origin and be life-threatening. As a result of the 2015 peat fires in Indonesia, over 100,000 people have died, half a million people had to be hospitalized, and economic damage ran into tens of billions of euros (Koplitz et al., 2016; Marlier et al., 2019; Kiely et al. 2021). Emissions from peatland drainage, degradation, and fires currently amount to over 2 billion metric tons of CO₂e annually and thus for almost 5% of all anthropogenic GHG emissions.

Without countermeasures, emissions from drained peatlands might consume between 12 and 41% of the GHG emissions budget we have left to keep global warming below 2 or 1.5 degrees by 2100 (Leifeld et al., 2019). Another projection shows that the entire land area of the Earth would by 2100 just be a net carbon sink if all currently intact peatlands are preserved and at least 60% of degraded peatlands are rewetted (Humpenöder et al., 2020). This means that the entire terrestrial carbon sink capacity would then be required to compensate for the carbon losses from the remaining 40% of degraded peatlands and would contribute nothing to the net carbon sink capacity required to meet the Paris climate targets (Convention on Wetlands, 2021a). For peatlands to be carbon neutral globally, 80% to 85% of drained peatlands need to be rewetted. Only if we rewet all drained peatlands worldwide, peatlands can once again fully serve their natural function as a global carbon sink (Convention on Wetlands, 2021b).

The German peatlands that have been drained for agriculture, forestry, or peat farming emit 53 million metric tons of GHGs annually (BMU, 2021), nearly 40% more than the Bełchatów lignite-fired power plant in Poland, which is considered the most climate-damaging thermal power plant in the world. The vast majority (83%) of these emissions come from agricultural land. The German Federal Environmental Agency currently assesses the damage caused by emitting one metric ton of CO₂ at 195 euros (Umweltbundesamt, 2020). This means that drained peat soils in Germany cause climate damage of 10 billion euros annually—a sum almost as high as the net value added of the entire German agricultural economy (Statista, 2023). These figures make abundantly clear that drained peatlands cause economic damage that far exceeds the value of the agricultural and forestry products produced on them.

In 2020, drained peatlands worldwide emitted 1.56 billion metric tons of CO₂e (Fig. 3). Just under 1.4 billion metric tons were due to CO₂ from microbial peat oxidation and dissolved organic carbon (DOC) discharge; the rest came from the 2.14 million metric tons of methane (from drainage ditches) and the 440,000 metric tons of N₂O (also from peat oxidation) (Greifswald Mire Centre, 2022).

Fig. 3

GHG emissions (in CO₂e as of 2020) from degraded peatlands of the members of the United Nations Framework Convention on Climate Change (UNFCCC), excluding peatland fires (using IPCC default values (Hiraischi et al., 2014; Greifswald Mire Centre, 2022)

In addition, there are, varying from year to year (and difficult to quantify), GHG emissions from open and smoldering peat fires in the order of 0.5 to 1 billion metric tons of CO₂e per year (Joosten, 2009; Rossi et al., 2016).

This means that 0.4% of the Earth’s land area accounts for nearly 5% of all global anthropogenic GHG emissions (cf. Ritchie et al., 2020). Major emission sources are Indonesia, the European Union, and Russia, whereas half of the EU share is taken up by Germany, Finland, and Poland (Fig. 3).

Other (Societal) Harms from Peatland Drainage

Beyond climate damage, there are many other problems associated with peatland drainage (Joosten, 2017). A lower water level leads directly to a reduction in evapotranspiration cooling of the landscape and to a loss of typical peatland biodiversity. The nitrogen mineralized by peat oxidation leads to the flushing out of nitrate and subsequently to the eutrophication of water bodies, including the oceans. Furthermore, because peat is primarily composed of water, drainage causes compaction of the peat body. This changes the peat’s hydraulic properties, reducing the peatland’s capacity to store water and to regulate runoff (Zeitz, 2016).

Mephistopheles Would Have Known Better ...

While Faust emphasized:

A swamp lies there below the hill,

Infecting everything I’ve done;

My last and greatest act of will

Succeeds when that foul pool is gone.

. and issued the order:

Report on progress every day,

The length of ditch earth dug away.

Mephistopheles said half aloud:

They speak, as was the word they gave,

Not quite of ditch, but more of – grave.

(FROM GOETHE, FAUST II).

A serious problem that has received too little attention so far is peatland subsidence. Drained peatlands lose—depending on climate and use—between a few millimeters and several centimeters of thickness per year due to microbial oxidation and compaction. The resulting subsidence of the peatland surface requires deepening of the drainage ditches if the peatland continues to be used conventionally. This in turn promotes further subsidence and requires further ditch deepening. This spiral is called the “vicious circle of peatland use.” Gravity-based drainage is thus becoming increasingly difficult and may finally, to keep the peatland dry, necessitate construction of polders with dikes and pumps. In the peatland-rich Netherlands, large areas have, after some 1000 years of peatland drainage, demonstrably sunk by over 8 m, and much of the country now lies below sea level (Erkens et al., 2016). Financially, the damage to roads and sewage infrastructure due to peatland subsidence there amounts to around 200 million euros per year, and it is estimated that by 2050 subsidence damage to buildings will amount to 80 billion euros (Van den Born et al., 2016; Tieleman, 2020).

Many peatlands in temperate latitudes, the subtropics, and the tropics are located near the ocean. Especially in often densely populated coastal areas, peatland subsidence increases the risks of flooding and the intrusion of salty seawater. While sea levels rise due to global warming, the adjacent peatland is literally bogged down. Considerable parts of the Malaysian and Indonesian peat swamps near the ocean, which have recently been drained for the cultivation of oil palm and pulpwood, will in the next decades be flooded by the sea due to intensive subsidence (Hooijer et al., 2015). Diking, poldering, and pumping − the interim solution tried in the Netherlands, northern Germany, England, California, and Florida to keep drained peatlands dry − will not work in Indonesia and Malaysia because of the huge extent of the areas and the enormous amounts of rainfall. It also would not stop subsidence and would achieve only an insignificant delay in the inevitable abandonment of this drainage-based land use (Dommain et al., 2016).

In more continental climates, frequent water level fluctuations lead to the formation of cracks in the drained peat, which prevent capillary water supply and thus lead to an even more frequent and deeper drying out of the soil. Due to the action of soil organisms, a loose, fine-grained, and water-repellent topsoil then develops, which finally can sustain at best only dry grassland species (Joosten et al., 2016; Zeitz, 2016). In this way, millions of hectares of former peat wetlands in Eastern Europe have, within a few decades, been transformed into deserts (Joosten et al., 2012).

Drainage-based peatland use is thus not only a disaster for the climate but also a threat to the productive potential of peatland soil.

Solutions and Challenges

Drainage-based peatland use is harmful to the climate, has no long-term prospects, and often entails a net social loss. Instead of continuing with outdated and unsustainable production methods, we should ask how we can manage peatlands without causing such grave environmental problems.

The answer is clear: peatlands must be wet! Wet peatlands must remain wet, drained peatlands must become wet again, and if we absolutely must use peatlands, we must use them wet (Joosten et al., 2012).

Threats to, and Protection of, the Remaining Natural Peatlands

Most of the world’s peatlands are still largely unused and undrained. But threats and actual damage are on the rise, even in areas that received little attention a few decades ago. One example is the rapid expansion of agriculture and forestry in the tropics, often accompanied by deforestation: plantations of oil palm, fiber wood, aloe, pineapple, and banana are encroaching on forests and peatlands, as are smallholder farms, also in significant quantities. While until recently only peatlands in Southeast Asia, especially Malaysia and western Indonesia (Sumatra and Kalimantan), fell victim to rapidly expanding drainage-based peatland use, recent years have seen increasing encroachment of exploitation on natural peatland areas on the island of New Guinea, in western Amazonia, and in West Africa. Something similar is happening in East African countries, such as Uganda, Rwanda, and Madagascar, where increasing population pressure is driving people to seek a livelihood in the last still unused areas, the peatlands (Joosten et al., 2012).

The damage from new infrastructure projects, such as roads or oil and gas exploration and extraction, is more local (but radiates out from there). Important sources of liquid energy are found in peatlands such as Prudhoe Bay (Alaska), the Pastaza-Marañón Foreland Basin (Peru), the Niger Delta (Nigeria), Siberia, and Kamchatka (Russia). The pipelines to the metropolises largely run through forest and peatland areas (Fig. 4).

Fig. 4

Peatland distribution and location of existing and planned oil and gas pipelines in the Russian Federation. (Data from Timashev, 2019; Kirpotin et al., 2021)

The huge forest peatlands in the Congo Basin, only recently surveyed and barely explored, have now been almost entirely licensed out to oil and gas explorers (Dargie et al., 2019; Global Witness, 2020). Oil exploration in the Alberta oil sands (Canada) is currently destroying peatlands on a large scale (Rooney et al., 2012). In the Hudson Bay Lowlands (Ontario, Canada), the second largest peatland area on Earth, there are currently 13,296 active mining claims for diamonds, chrome, nickel, copper, gold, and platinum, covering approximately 2127 km² within Ontario’s “Ring of Fire” (Harris et al., 2022; McIntosh, 2021; Ministry of Mines 2022). For peatlands in Mongolia and mountainous areas like the Andes, mining is also a strong threat, as is overgrazing (Assessment Report, 2017; Maldonado Fonkén, 2014/2015).

In 2017, Rwanda opened its first peat-fired power plant in Gishoma, on the border to the Democratic Republic of Congo. Another and much larger peat-fired power plant in Gisagara, in the east of the country, is soon to feed 80 megawatts (MW) into the national grid. Currently, only 25% of households have access to the 190 MW of electricity generated in Rwanda, but capacity is set to increase to 563 MW. This increase will be achieved partly with peat extracted from the large valley peatland that runs along the border with Burundi (Cole, 2017; Mugerwa et al., 2019).

Stopping such dangerous developments is of course anything but easy. Arlette Soudan-Nonault, Minister for the Environment in the Republic of Congo, recently put it in a nutshell: peatlands are an important ecosystem not only for the two Congos “but also for the entire planet.” The Republic of Congo, she said, is committed to protecting the peatlands. However, “we are not naïve, and we do not intend to stop our development just so the planet can breathe easier. The invaluable ecosystem services that our peatlands and forests render to the planet cannot remain free forever, to the detriment of our population’s aspiration for well-being” (Cannon, 2021). The situation is thus as clear as it is precarious: on the one hand, we cannot expect (poor) countries to provide services for the whole world without being adequately paid for them; on the other hand, they are sawing at the branch they are sitting on, because short-term gains will quickly turn into major disadvantages, also for their own populations. We from the global North, especially we Europeans, are probably least able to communicate this successfully: we have no credibility because we have cleared a large part of our forests and drained our peatlands—and apparently become rich in the process. This is why it is so important that with the UN Global Peatlands Initiative (2023), the Brazzaville Declaration (UNEP, 2018), as well as the Peatlands Resolution of the United Nations Environmental Assembly (UNEA, 2019), a South-South link has been established in which the tropical peatland giants exchange views and consult with one another. Thus, to share lessons learned, Indonesia has sent many of its specialists to Africa and invited representatives from the two Congos and Peru to Indonesia.

Rewetting of Drained Peatlands

The rewetting of drained peatlands is the ultimate solution to the problems outlined above. Rewetting, that is, raising the groundwater table to or above the peatland surface, significantly reduces GHG emissions and can reactivate carbon sequestration (Wilson et al., 2016; Nugent et al., 2018; Mrotzek et al., 2020). While drained peatlands release nitrate through peat mineralization and agricultural use, rewetted peatlands cost-effectively remove this fertilizer through the process of denitrification (which produces molecular nitrogen; Trepel, 2010). However, because rewetting of overfertilized areas can also lead to the release of phosphate, it makes sense to assess this risk in advance (Emsens et al., 2017).

Rewetted peatlands also protect against flooding. This is so because peatlands suffer less damage from floods (there is no risk of crop failure) and also can absorb and retard flood waters, thereby protecting sensitive areas downstream (Joosten et al., 2015). Since rewetted peatlands delay the runoff of water from the landscape, the groundwater reserves in the catchment area increase—and this, together with flood retention, is an important adaptation to climate change which, apart from general warming, also leads to redistributed precipitation patterns, to more frequent and more intensive heavy rainfalls, and to longer dry spells (Quante & Colijn, 2016).

Rewetting changes the heat balance towards more cooling because more of the incident solar energy is used for evaporation, leaving less for significant heating (see also Chapter “Strengthen Terrestrial Water Cycles”). Over the peatland area of the Kieve polder in Mecklenburg-Western Pomerania, Germany, rewetting has produced a cooling effect of about 3 watts per square meter and has thus more than compensated for the GHG-induced warming of approximately 2.6 W/m² since 1750 (Joosten et al., 2015). With large-scale peatland rewetting, we can thus expect regional cooling effects. Last but not least, the increase in peatland biodiversity must be mentioned. In Mecklenburg-Western Pomerania, a few years after the rewetting of formerly heavily drained river valley peatlands, many peatland-typical and some highly endangered bird species have reestablished themselves (Herold, 2012).

In recent decades, several hundred thousand hectares of peatland have been rewetted in Europe (Tanneberger et al., 2017a). This sounds good at first, but in view of some 30 million hectares of drained peatlands in Europe, it must be considered a “drop in the ocean.” Many rewetted peatlands are nature reserves, or abandoned, more or less exhausted peat extraction areas, or areas in very extensive use, with correspondingly relatively low emissions.

In all areas dedicated to “peatland nature conservation,” rewetting is in any case the method of choice. Only a small proportion of peatlands (such as peat meadows and peat heaths) need minor drainage (and active management) to preserve their typical, anthropogenic, semi-natural biodiversity (Joosten, 2017). The centuries-long focus on drainage has fostered in Europe (even among conservationists!) a far too “dry” idea of how wet a living peatland is supposed to be. Since 1992, many hundreds of peatlands have been rewetted and revitalized through the European Union’s LIFE programme (Camarsa et al., 2015).

Former peat extraction areas have been rewetted on a large scale in Germany, Belarus, and Russia − in Russia especially after the huge peat fires of 2011 (Tanneberger & Wichtmann, 2011; Barthelmes et al., 2021; Sirin et al., 2021). In Ireland, the parastatal peat company Bord na Móna has completely stopped peat extraction in 2021 and begun to restore over 30,000 hectares of peat extraction areas—as a core element of the Irish climate strategy (Bord na Móna, 2021; Kelleher, 2021). The largest such projects in the UK are mainly located on blanket bogs, which are used (very) extensively for sheep farming and grouse and deer hunting. In part, their rewetting is carried out as compensation for the construction of wind farms (Grouse Moor Management Review Group, 2019).

Rewetting of Peatlands in Intensive Use: Paludiculture

Most urgent for the climate and most challenging politically is the rewetting of heavily drained peatlands that are intensively farmed. This includes vegetable cultivation in California (to supply San Francisco), carrot cultivation in Norway, lettuce and potato cultivation in the east-anglian fens (UK), potato cultivation in the Teufelsmoor and Donaumoos (Germany) as well as cultivation of maize, Miscanthus, and reed canary grass (for “bio energy” in Germany and the Nordic countries), of sugar cane (Florida), of pulpwood and rubber (Indonesia), and of oil palm (mainly in Southeast Asia and more recently in New Guinea, Africa, and Amazonia). Dairy farming is also very common on drained peatlands (as in the Netherlands, Germany, and Poland).

Until now, peatlands have mostly been taken out of use after rewetting and converted into new “wet wilderness areas” or kept in low intensity management for biodiversity purposes. But we will no longer be able to afford doing this everywhere. All these peatlands have been drained to produce biomass, of which we need more and more as the human population continues to increase and we need to reduce the abject poverty of many. Moreover, in Paris 2015, humanity has agreed to largely decarbonize the world in the coming decades. Most fossil raw materials and fuels − coal, oil, gas, ores, and minerals − are to be replaced by biomass, which must be supplied by sustainable agriculture and forestry. We can no longer afford to degrade valuable production areas through (additional) drainage or to take degraded and then rewetted peatlands out of production on a large scale, unless we reduce the consumption of animal protein substantially. So long as a different consumption pattern has not become widely established, we must urgently develop new land use options that avoid the environmental damage of conventional peatland use while enabling us to use peatlands productively (Joosten et al., 2012; Joosten, 2017). Such uses exist, they are known as “paludicultures” (Wichtmann et al., 2016).

Paludicultures

are agricultural and forestry systems that aim to produce crop or livestock products on peat soils, conserving the carbon stock of the peat body and minimizing GHG emissions from the peat soil. Whether these goals are achieved depends not only on which crops are grown, but mainly on whether the growing conditions preserve the peat soil and keep it permanently wet (Wichtmann et al. 2016; Convention on Wetlands, 2021a).

Paludicultures make it possible to maintain productive agriculture and forestry while also restoring important ecosystem services of wet peatlands: reduction of GHG emissions, improvement of water quality, flood protection, evaporative cooling, maintenance and increase of peatland biodiversity. Paludiculture, by definition, stops peatland subsidence and has the potential to preserve employment in rural areas, to enable regional value creation, and to regionalize the supply of raw materials and energy (Wichtmann et al., 2016).

Paludiculture methods are currently being tested worldwide (Ziegler et al., 2021). In Europe, on nutrient-rich fen peatland sites, the focus is on reeds (for high-quality building materials), cattails (for building panels, insulation, animal feed, peat and plastic substitutes, etc.), unspecified biomass (for heat and energy) and alder (for furniture and veneers); the raising of water buffalo (for meat) is also interesting. On nutrient-poorer bog soils (cut-over bogs and bog grasslands), the focus is on peat mosses (as a substitute for fossil peat in horticulture) and sundew (for medicinal purposes) (Wichtmann et al., 2016).

The Southeast Asian lowlands provide more options. There are 1376 species of higher plants growing in the swamp forests there, of which 534 (39%) are already being used: 222 species produce useful wood, 221 have medicinal uses, 165 species provide food (such as fruits, nuts, and oils), another 165 are suitable for “other uses” (such as latex, fuels, and dyes). Many species have multiple uses, 81 non-timber products are “economically important” (Giesen, 2013, 2015). As rural communities are essentially farming communities, and paludiculture enables sustainable farming (albeit with modified techniques and alternative crops), paludiculture has great potential to preserve and revitalize local livelihoods while re-wetting drained peatlands (Convention on Wetlands, 2021a).

Paludiculture can also be a sensible way of protecting species and habitats (Närmann et al., 2021; Martens et al., 2023). Successful examples of the combination of species conservation and paludiculture are the occurrence of the globally threatened sedge warbler (Acrocephalus paludicola) in commercially used reed areas in western Poland (Tanneberger et al., 2009) and the spontaneous mass occurrence of sundew (Drosera rotundifolia and D. intermedia), cranberry (Vaccinium oxycoccos), and beak rush (Rhynchospora alba) as well as rare arthropods (such as spiders and dragonflies) on peatmoss farms in Lower Saxony, Germany (Muster et al., 2015, 2020; Gaudig & Krebs, 2016).

The economic benefits are so promising that one wonders why paludiculture has not yet been implemented on a large scale. The following are some obstacles that should urgently be eliminated:

• Paludiculture is fighting against the historical legacy of 10,000 years of dry agriculture. Our society does not have a “wet mentality,” has never learned to farm in the wet and always striven to drain water as quickly as possible.

• Current rules and laws are not adapted to wet agriculture. In many places, landowners are obliged to maintain their ditches and drain their land—old regulations that still have an impact today. Farmers who convert to paludiculture receive lower EU subsidies (direct payments), as many paludiculture crops are not recognized as agricultural crops. This is changing in 2023 with the new EU agricultural rules. The ban on grassland conversion, introduced to protect soil carbon and biodiversity, is blocking the implementation of some paludiculture practices, even though they are more valuable than drained peatland grassland in terms of carbon and biodiversity protection.

• Incentives still exist to continue drainage-based management of peatlands, notably direct payments under the EU’s Common Agricultural Policy (CAP).

• Paludiculture may create biotope types (e.g., reeds) that are protected by law and whose use is subject to legal restrictions (Czybulka & Kölsch, 2016).

Improving this situation requires creativity—and goodwill on the part of the authorities—in addition to the thoughtful and swift adaptation of rules and laws.

Paludiculture is more than just switching from one crop to another. It usually requires a redesign of the entire production chain, starting with acceptance and training, followed by selection and breeding of suitable plant species. New techniques must be developed, new infrastructure and logistics planned and implemented. It takes time to develop a fully integrated value chain. Those embarking on paludiculture need curiosity and patience as many crops are still in the pilot stage and in need of further research and development (Wichtmann et al., 2016).

A Future Strategy for Our Peatlands

Peatland rewetting is one of the most efficient land-based climate protection measures. It is actually peerless. But it requires either a complete cessation of productive land use or a comprehensive transformation to new, wet forms of cultivation. Under the Paris Climate Agreement, Germany must re-wet 50,000 hectares of drained peatlands by 2050—annually. For the European Union the commitment is 500,000 hectares, for Europe 1000,000, and worldwide 2,000,000 hectares per year. To meet these huge targets, the peatland nations need strategies (Fig. 5).

Fig. 5

Development paths and milestones for the various land use categories on peat soils in Germany pursuant to the overall emissions path recommended by the IPCC (2018). (After Tanneberger et al., 2021). Dry = deeply drained (strongly peat-consuming); wet = slightly drained (weakly peat-consuming); wet = under water (peat-preserving)

Just as lignite miners were not asked to organize the German coal phase-out, the phase-out of drainage-based peatland use must be seen as a task for society as a whole, and one of similar dimensions. If one takes the German coal phase-out budget (50–57 billion euros) as indicative of what society is willing to pay to reduce GHG emissions in a socially acceptable way, a budget of 36–41 billion euros for the climate protection measure “rewetting of arable land and grassland on peat soils” should be politically justifiable (Sommer & Lakner, 2021).

Such a cross-sectoral peatland protection strategy requires ambitious goals and policies, a time frame with defined intermediate steps, and action recommendations for specific actors. A broad-based peatland protection commission (similar to the German coal commission, Kommission „Wachstum, Strukturwandel und Beschäftigung“, 2019) should prepare and accompany the phase-out of drainage-based peatland use. To this end, measures to strengthen structures and promote innovation are essential for the affected peatland regions. Peatland rewetting should here be integrated (with the involvement of water resource management) into the reorganization of landscape hydrology, which in any case is needed to adapt to climate change.

Because of the “species crisis,” part of today’s agriculturally used peatland must be restored to protect biodiversity. In this way, climate and biodiversity goals can be efficiently combined. As most paludiculture is still in the experimental phase, research and development must be more strongly promoted, focusing here on the unique structural and physiological properties of wetland-adapted plants so as to avoid competition with “dry” agriculture and thereby to enable wet agriculture to become self-sustaining in the medium term and to assert itself in the economic mainstream.

All these tasks can and should be state responsibilities. But their necessary, massively expansive implementation cannot be realized in a fully centralized manner. The purchase of all drained areas is too expensive: land prices are largely determined by rights, tax benefits, and subsidies (such as direct state payments)—ultimately, we taxpayers would be paying twice. The size of the relevant area as well as the necessary time flexibility and creativity require conditions that can be better supplied by the “free market.”

A Fast-Track Paludiculture Programme Should Aim for

• simplification of the legal rules relating to implementation (laws governing water management, planning, agriculture, public procurement, land consolidation, etc.) and expansion of planning and technical capacities;

• identification of promising crops;

• selection and breeding to increase productivity and quality;

• improvement of farming and processing technologies;

• cross-company standardization of processing procedures;

• creation by the EU of a Life Cycle Assessment (LCA)-based Conformité Européenne (CE) certification to give preference to paludiculture products;

• market incentive programs for paludiculture products (e.g., in the sectors construction, horticultural substrates, energy, etc.).

Rewarding climate protection services should facilitate these measures. Successful peatland rewetting can avoid 20–25 metric tons of CO₂e per hectare per year in Central Europe (Joosten et al., 2016). More and more businesses, institutions, and cities are setting themselves ever more ambitious goals on the path to climate neutrality, goals they often cannot achieve on their own within their self-chosen schedules. Consequently, there is rapid increase in the demand for, and price of carbon “offsets.” The price of a metric ton of CO₂ in the leading EU Emission Trading System (ETS) market has increased 20-fold in the last 5 years and has in 2023 temporarily exceeded 100 euros per metric ton of CO₂ (https://tradingeconomics.com/commodity/carbon). How prices of carbon certificates from peatland rewetting will develop depends on the quality, that is, the reliability of the product; but similar increases might happen here, as is suggested by the experience with the regional MoorFutures® carbon certificates (https://www.moorfutures.de). Performance-based remuneration from the sale of carbon certificates can facilitate a rapid start-up of peatland rewetting, making it economically competitive with drainage-based, conventional peatland use until paludiculture will be technically fully developed and economically self-sustaining. The state should promote such carbon markets or at least not impede initiatives to create them.

Such a peatland emission trading system requires the development of:

• efficient and transparent Measuring, Reporting, Verification (MRV) approaches (through adaptation/ elaboration of existing standards and methods);

• similar processes for CO₂ sequestration (sinks) in paludi soils and products (cf. Harvested Wood Products);

• regional agencies and specialist bodies for emission assessment and certification, and

• reliable (national or regional) CO₂ exchanges.

A Peatland Emission Trading System Might Function as Follows (Isermeyer et al., 2019)

• The state issues landowners cost-free emission rights in the amount of their current emissions each year until 2045. These rights can be used to continue drainage-based agricultural production or, after rewetting, be sold as CO₂ certificates on the exchange.

• The state guarantees a minimum price for the CO₂ certificates (perhaps 60 euros per metric ton of CO₂ in 2025, rising to 100 euros in 2040) and, if the market price does not reach this threshold, pays the difference.

• The landowner may use the rewetted areas for paludiculture.

• The issuance of free emission rights ends by 2045. Landowners wanting to continue conventional use of drained peat soils will then have to buy the necessary emission rights on the exchange.

• Politics determines how to proceed if, among the landowners of a hydrologically connected area, most favor but some reject rewetting; the law is to be adjusted accordingly.¹

The advantages of such a system are:

• high attractiveness for users: the land remains in private hands, and the owners decide how to manage it;

• rapid rewetting, because it is more profitable the sooner it is initiated;

• a fair balancing of interests: legitimate expectations are protected in the medium term and the polluter-pays principle prevails long-term.

After 2045/50—because everyone must be at “net zero”—it will no longer be possible to generate carbon certificates by avoiding CO₂ emissions. Income from agricultural peatlands must then be secured differently: through (1) competitive paludiculture, (2) CO₂ sequestration, and/or (3) rewards for other social benefits (Joosten et al., 2015).

Conclusion

Although peatlands contain more carbon than the entire global forest biomass, their importance has long been overlooked. Drained peatlands (0.4% of the world’s land area) cause disproportionately high anthropogenic GHG emissions amounting to almost 5% of the worldwide total. To meet the Paris climate goals, all intact peatlands must remain wet, and drained peatlands must be rewetted; peatland use should take place only under wet conditions. The greatest challenges for rewetting lie with the peatlands now used intensively for agriculture. There is an urgent need to develop and implement (wet) production methods (paludiculture) that allow productive use of peatlands while avoiding the environmental harm from conventional peatland use. This requires the state to implement a cross-sectoral peatland protection strategy with measures to strengthen structures and promote innovation. The massive implementation on the ground, however, is best left to the self-directed momentum of enterprises and markets steered by climate protection rewards to facilitate a rapid start-up of peatland rewetting. In this way, companies can compete with drainage-based peatland use until paludiculture is technically fully mature and economically self-sustaining.

Peatland must be wet: for the peat, for the land, for the climate, forever!