Facts about peatlands

Formation and distribution

Formation: Peatlands exist where a high groundwater table limits the decomposition of organic material.

Thus, production of organic matter is higher than decomposition and the so called peat is formed [1].

In Central Europe, peatlands were formed since c. 10,000 years ago, when the glaciers melted after the last glacial period. The water which was formerly bound in the glaciers now lifted the groundwater table and peatlands developed. In near-natural peatland sites this process is still continuing.

Even though mineralization is limited by high ground water tables, only 2-16% of the fresh organic material is transformed into peat while the rest is mineralized. So mires on average form a 0.5mm layer of peat per year, under optimal conditions values up to 1mm can be reached [3,5].

Distribution: Peatlands exist on all continents, from tropical to arctic zones, and from sea level to high altitude.

Peatlands cover only roughly 3% of the global land surface, but contain roughly 20% of the total carbon stored in all terrestrial ecosystems. Thus, peatlands are the most space-effective carbon stocks of all terrestrial ecosystems [7].

Proportional the total size of the country, Finland was the country with highest amount of areas covered with peat worldwide. Roughly one third of Finlands territory was originally covered with peat.

The Wasjugan peatland (Siberia) is considered to be the biggest peatland in the world. It covers more than 5 millions hectare, which is roughly four times the size of the German federal state Schleswig-Holstein [6].

Initially mires covered 4-5% of Germanys land surface (estimates vary between 1.4 and 1.8 million ha). Due to drainage and subsequent use currently only 25,000 ha can be seen as mires, i.e. peat accumulating systems (2% of the former mire area) [4].

Threatening

Agriculture: is considered to be the main driver (50%) for global mire losses, followed by forestry (30%).

In contrast to what is often thought peat extraction (mainly for fertiliser, substrate, energy, chemistry, and bedding) is responsible for “only” 10% of these losses. The remaining 10% of peatland losses can be attributed to urbanization and infrastructure development.

Drainage of peatlands: changes their function from a CO2 sink to a CO2 source.

Drained peatlands in Germany used for potato cultivation emit 37t CO2 equivalent per hectare per year. This amount equals a ride of 185,000 km in a medium-sized car.

Drainage causes fundamental changes in peat-chemistry and -physics. Different processes cause subsidence (loss of height) of 1-2cm per year in middle latitudes. In Southeast Asia values of up to 7cm per year can be reached. In an English peatland north of Cambridge subsidence of 4m took place since 1848 [5,7].

Historical development

Because of their site characteristics („too wet to drive, too dry to swim“) peatlands were the last areas which experienced intensive use. Nevertheless archaeological studies revealed that peatlands were already used for hunting and gathering during Stone Age [5,7].

Earliest human interventions: into peatland ecosystems often had a positive effect on peatlands.

Forest clearings increased the groundwater recharge which led to peatland expansions in many areas [2].

First smallscale drainage of peatlands in Northern Germany took place in the 13th century. Cistercian monks used the drained areas to cut fodder and litter once a year [5,7].

Livestock grazing is common in near-natural as well as drained peatlands since millennia. Livestock can serve as natural landscape managers, but with increasing stocking density detrimental effects may prevail.

Peatlands were also used for fodder and litter production, in some countries even today. Especially in boreal countries fens were the most important areas for hay production. After cessation of traditional extensive mowing competitive species like reed or alder often encroached on the former open species rich areas.

Intensification: Drainage was intensified in the 18th century, partly by governmental ordered and financed programs like the edict of cultivation for peatlands by Friedrich II 1765 [7].

The 19th century marked beginning the most intensive period of peatland drainage. Technical approaches, like the use of drainage tubes made of clay, supported the intensification [7].

Peat was and is extracted for several purposes: energy generation, substrate and growing media in horticulture and building and insulation material. But also bizarre uses like whiskey flavouring, textile material and therapeutic mud baths exist [4].

Because of limited accessibility peatlands were used since Roman era in military defence. For the same reason prisons and labour camps were also often located in peatlands [4].

Peatlands represent areas with a natural water surplus. Because of that they were often inundated and used for hydropower generation. But also for commercial fish farming peatlands were inundated, e.g. 200 km² of fishponds in Belarusian Poley’se [4].

Komplexmelioration: Drainage efforts culminated in the so called „Komplexmelioration“ in the GDR.

From the 1960ies until the collapse of the GDR in 1990 on plenty of former extensively drained areas drainage measures were intensified (e.g. widening of drainage channels). The „Komplexmelioration“ should match the agricultural area with the vehicle fleet [7].

Since the 1990s: sustainable land-use practices for peatlands summarized under the catchphrase „paludiculture“ developed.

In contrast to the conventional drainage-based use paludiculture uses wet and rewetted peatlands. Thus peat is conserved or even newly formed; greenhouse gas emissions and eutrophication are minimized [5,7].

Sources and further information

[1]   Dierssen K, Dierssen B (2001): Moore. Verlag Eugen Ulmer, Stuttgart.

[2]   Ellenberg H, Leuschner C (2010): Vegetation Mitteleuropas mit den Alpen.
Verlag Eugen Ulmer Stuttgart.

[3]   Göttlich K (eds.) (1990): Moor- und Torfkunde. Schweizerbart Science Publisher, Stuttgart.

[4]   Joosten H, Tanneberger F, Moen A (eds.) (2017): Mires and peatlands of Europe.
Schweizerbart Science Publisher, Stuttgart.

[5]   Succow M, Joosten H (eds.) (2001): Landschaftsökologische Moorkunde.
Schweizerbart Science Publisher, Stuttgart.

[6]   Tanneberger F, Hahne W, Joosten H (2003): Wohin auch das Auge blicket:
Moore, Moorforschung und Moorschutz in Westsibirien. Telma 33: 209-229.

[7]   Wichtmann W, Schröder C, Joosten H (eds.) (2016): Paludikultur –
Bewirtschaftung nasser Moore. Schweizerbart Science Publisher, Stuttgart.