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 organic matter in the peat. As a result, the vast amounts of stored carbon are released back into the atmosphere, exacerbating global warming, and the ecosystem services which rely on the peatland’s wet conditions are prevented. These drier conditions also increase the risk of fire, with the peat acting as an abundant source of fuel. These can be truly devastating: the 2015 Indonesian peat fires caused the deaths of 100,000 people.
In Europe, peat has been directly cut and removed from peatlands for centuries. In the past, this was predominantly dried out and used for fuel. But now the primary use of peat is in compost, because water and nutrient content can be easily controlled to create optimal growing conditions. Peat compost has been used by many private gardeners, but also underpins much food production, especially of mushrooms. Every year, an estimated 30 million cubic metres of peat is used globally for compost.
In the UK, an additional pressure is the intentional burning of peatlands by the grouse-shooting industry. The intention is to encourage the new growth of fresh heather shoots, for the grouse to eat. However, burning kills the Sphagnum and changes the physical composition of the upper peat layers, altering the peatland’s hydrology and releasing an estimated 250,000 tonnes of CO2 every year. Pollution from industrial activities such as coal power stations has also played a key role in the UK and is responsible for widespread degradation in areas such as the South Pennines.
Peatland degradation contributes more to annual global greenhouse gas emissions than shipping and aviation combined. Added to this, a positive-feedback tipping point may be reached where global warming leads to the thawing of permafrost peatlands and the release of vast amounts of CO2 and CH4. Climate change will further degrade peatlands via changes in precipitation patterns and increases in evapotranspiration that will alter the ecosystem’s characteristic hydrology.
The fight for Peatlands
Despite the challenges, there are inspiring people all around the world fighting for peatlands to be protected and restored. This ranges from local community groups, like the Camosun Bog Restoration Group restoring an urban bog in Vancouver, and the Friends of the Lye Valley restoring an alkaline fen in Oxford, to youth-led awareness-raising collectives like Re-Peat and also international governmental agreements such as the Ramsar Convention. Exciting innovations such as ‘paludiculture’, which is the sustainable use of wet and rewetted peatlands without drainage are also aiding peatland restoration all across the world.
Peatlands are crucial ecosystems for the well-being of the planet, and deadly when mistreated. It is vital that we regain an appreciation of the beauty and value of this underdog ecosystem, and implement policies and industry practices that reflect this.
Jamie is a 3rd year Biologist at Somerville College, Oxford. He is a member of Re-Peat and has written on various topics surrounding peatlands and the environment, including poetry, which you can find at his Twitter @jamie__walks. Jamie hopes to go into research surrounding wetland ecosystem functioning and bryophytes.
Art by Shristhi Aditi Patra.