What are peatlands?

Peat is the accumulation of organic material (e.g., plants or mosses) that has been formed on the spot and has not been transported after its formation. Where the water level  is  stable  near  the  peat surface  (just  below,  at,  or  just above), the  remains  of  dead  plants  and  mosses  do  not  fully  decompose due to the absence of oxygen (i.e., aerobic decomposition is limited), and therefore  a layer of organic material accumulates over time where litter deposition exceeds anaerobic decomposition (i.e., in the absence of oxygen). A peatland is an area with a naturally accumulated peat layer at the surface (with or without surface vegetation). According to different definitions, this layer needs to be at least 30 cm thick for a soil to be classified as a peat.

Peat profile

Fig. 1. A typical peat profile.

Types of peatland

There are 6 principal global types:

(1) Blanket mires: Rain-fed, generally 1-3 m deep. Location: mainly in Ireland and the UK. The UK alone has around 13 percent of the total global blanket mire area. They generally develop in cool climates with small seasonal temperature fluctuations and over one meter of rainfall and over 160 rain days each year.

Fig. 2 Blanket Mire

Fig. 2.Typical blanket mire.

(2) Raised mires: Rain-fed, potentially deep peatlands. Location: Northern Europe and North America, as well as in the former USSR and parts of the southern hemisphere.

Fig. 3 Raised mire

Fig. 3. Typical raised mire.

(3) String mires: Flat or concave peatlands with a string-like pattern of hummocks. Location: primarily northern Scandinavia, but have been found in the western parts of the former USSR and in North America.

Fig. 4 String mire

Fig. 4. Typical string mire. Source: coffeentrees.tumblr.com

(4) Tundra mires: Peatlands with a shallow peat layer, ~50 cm thick. They form in permafrost areas in Alaska, Canada, and the former USSR, covering ~110,000 to 160,000 km².

Fig. 5 Tundra mire

Fig. 5. Typical tundra mire. Source:www.rusnature.info

(5) Palsa mires: A type of peatland typified by high mounds, each with a permanently frozen core, with wet depressions between the mounds. Location: former USSR, Canada and parts of Scandinavia.

Fig. 6 Palsa Mire

Fig. 6. Typical Paslsa mire. Source: www.nationalparks.fi

(6) Peat swamps: Forested peatlands (both rain- and groundwater-fed), are commonly found in high rainfall regions. This type of peatland covers ~350,000 km². Location: Southeast Asia, central Africa, the Amazon basin and the Everglades in Florida, USA.

Fig. 7 Swamp Mire - Uganda

Fig. 7. Typical peat swamp. Source: Dr Sophie Green, University of Leicester.

Where are peatlands found?

Peatlands are found in at least 175 countries and cover around 4 million km² or 3% of the world’s land area. The largest peat deposits are located in northern Europe, North America, and Southeast Asia (see below). Peatlands within Southeast Asia cover 27.1 Mha, of which over 22.5 Mha are within Indonesia (12% of the land area). Indonesia has more tropical peat land and mangrove forests than any other nation on earth.

Fig. 8 Peatland distribution map

Fig. 8. Worldwide distribution map of peatlands.

Peatland ecosystem benefits

Peatlands perform an array of ecological functions that we have only recently begun to fully document. There are numerous environmental benefits that peatlands provide:

Fig. 9 Ecosystem Services

Fig. 9. Summary of ecosystem services that peatlands provide.

The overuse, exploitation and drainage of peatland habitats have a host of environmental implications such as land subsidence, wildfires and disruption of the global carbon balance.

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