The Underdog Ecosystem

Updated: Sep 10

Peatlands' Vital Contribution to the Global Climate

At a peatland in Southern England, standing on the boardwalk above a floating patch of luminescent moss and the dark earth beneath, I am filled with quiet awe at the global importance of this type of ecosystem. Found on every continent, peatlands range from this small patch a mile from my front door to vast expanses in the Siberian tundra above the permafrost, to the raised bogs of Tierra del Fuego and the Congolese swamp forests that are larger than England, identified just 4 years ago. In total, this amounts to just 3 per cent of the Earth’s surface, yet peatlands are the largest terrestrial carbon store, storing twice as much carbon as all the world’s forests combined.

All of these diverse habitats are wetlands that contain peat, which is plant matter that has been unable to fully decompose, primarily due to the lack of oxygen in the waterlogged surroundings. This inhibits microbial activity because the microbes cannot aerobically respire. As a result, carbon that is fixed in plants is buried underwater before it can be released back into the atmosphere via microbial decomposition.

Many peatlands are still actively forming peat and sequestering carbon (‘mires’) but some represent only historic carbon stores. Some receive water only from rain (the bogs) while others are connected to groundwater sources (the fens). Peatlands also vary according to their chemistry, with differing pH and nutrient amounts. Peatlands may be flat and open, without a tree in sight and open pools of water forming in the landscape, or they may be slightly drier, with hummocked areas in which trees can grow.

Benefits across species

Peatlands in temperate regions like the UK are dominated by Sphagnum. This diverse moss genus is an ecosystem engineer, creating the acidic and waterlogged conditions in which it can thrive and outcompete vascular plants. Sphagnum consists primarily of dead, hollowed-out cells, which allows them to absorb up to 20x their weight in water and makes them even more resistant to decomposition, further facilitating peat formation.

Tropical peatlands, on the other hand, are often forested. In the swamp-forests of Southeast Asia, for example, peat is formed by wood falling beneath the water’s surface. This can lead to enormous peat depths, commonly more than 10m deep (compared to roughly 40cm in temperate regions), and therefore to massive carbon storage.

As well as regulating global climate through storing carbon, peatlands regulate local climatic conditions by lowering the air temperature via evapotranspiration. Peatlands also purify drinking water, because as rain percolates through the Sphagnum and peat, contaminants are filtered out and the resulting water requires minimal further treatment. In the UK, 70 per cent of drinking water is derived from areas dominated by peatland.

Peatlands are not just beneficial to humans, but also support many other species. These often have fascinating adaptations to the peatland environment, such as the spider Pirata piscatorius that lives in the hollowed-out centre of Sphagnum moss. Birds also need peatlands, such as the curlew which nests in bogs and feeds on the abundant invertebrates in the peatland’s upper layers. In the Indonesian and Malaysian peat swamps, very high numbers of endemic fish and invertebrates are supported, as well as orangutans which are retreating from the destruction of the wider rainforest.

Degraded landscapes

Despite all the benefits they bring to humans and wildlife, peatlands are being degraded. Globally, 16 per cent of all peatlands have been drained, while in the UK 80 per cent are in a degraded state. The main global pressure is drainage for agriculture, although there are other regional and global threats. Upon draining, oxygen becomes no longer limiting, allowing microorganisms to fully break down the org