For gardeners, peat’s ability to retain water makes it a beloved soil amendment that’s often added to potting mixes. But the real superpower of this unique organic material—composed of vegetation that has decayed over long periods of time in wet, low-oxygen conditions—is its ability to sequester carbon and keep a warming planet cool. 

Although peat covers only 3% of the world’s land area, it stores up to 44% of the planet’s soil carbon. That’s more than all the world’s forests and other vegetation put together. In fact, 1 hectare of healthy peat only 30 cm deep stores more carbon than a hectare of rainforest. When you consider that peatlands in the northern hemisphere’s boreal regions—estimated to make up 80% of the world’s peat-producing areas—have an average peat depth of around 2 m deep, that’s a lot of carbon.

The secret to peat’s creation lies in the soggy conditions in which the vegetation decomposes. Normally when plants die they release the carbon that they have absorbed during photosynthesis back into the atmosphere. In peatlands—the wetlands that produce peat, which may include marshes, bogs, mires, and fens—the waterlogged and often acidic conditions cause a chemical reaction that mummifies decaying vegetation, such as sphagnum mosses, sedges, and shrubs. As more vegetation grows and decays on the surface of the wetland, it compresses layer upon layer to form peat. But this doesn’t happen overnight: it takes about 10 years for 1 cm of peat to form, meaning that an area of peat just 10 cm deep represents 100 years of accumulation.

A slow decay

In a corner of the Metro Vancouver municipality of Delta, the slow, soggy decaying process has been taking place for over 4,000 years. The result is Burns Bog. To learn more about this unique place, I reached out to Don DeMill, whose lifetime of work in the bog and knowledge of its ecosystem has led the Burns Bog Conservation Society to refer to him as their “science advisor.”

“Over its long history, Burns Bog has built up a millimetre of peat each year, to a depth of 4 m,” DeMill told me in a phone interview. 

Even though the peat of Burns Bog is getting fractionally deeper every year, the bog’s overall size has shrunk. Of the original 4,000-5,000 hectares, only 3,000 remain. Industrial development and highway construction along the fringes of the wetland have decreased its size. Peat was extracted from Burns Bog to make incendiary bombs during World War II and was harvested for horticultural and agricultural use up until the 1980s.

Peat covers 3% of the world’s land area, but stores up to 44% of the planet’s soil carbon.

Those past actions still affect the bog. Peat harvesting not only removes the carbon-sink material itself, but also changes the hydrology of the ecosystem. Typically, when peat is harvested, a main ditch is dug along the perimeter of the peatland to drain water out of it. Shallower ditches that drain into the main peripheral ditch are then dug parallel to one another. A rotary tiller is used to remove surface vegetation, exposing the underlying peat, and the harvest fields are given a convex shape that improves drainage. Once the water content is reduced by 50%, the underlying peat can be removed by cutting or using vacuum harvesting machinery. 

“For over 10 years, I measured the water levels on the edge of Burns Bog,” DeMill says. “They continued to drop between 1 to 2 cm a year because of past drainage.”

Peat in peril 

Burns Bog is not alone in its plight. Despite peat’s ecological service to the planet and its ongoing sequestration of legacy greenhouse gases and carbon, almost 500,000 hectares of peatland are destroyed annually through human activity. According to the Global Peatlands Initiative, if this rate of degradation continues, it will consume 12% of the emissions budget needed to keep global warming below 2°C.

However, the biggest human threat to peat comes not from horticultural use, but from drainage for agriculture. For example, the total area of peatlands in Asia used for agriculture is estimated at 80,000 square km, and more than 95% of Germany’s peatlands have been drained for agricultural or forestry use. 

But these are not the only causes of peat’s demise. Its carbon-rich nature makes it an excellent heat and fuel source. People have burned peat for fuel since Roman times, and today it’s still used for heat and power in Finland, Ireland, and Sweden.

In England, the sale of peat for use in the amateur horticulture sector will be banned by the end of 2024.

And then there’s climate change. With summers growing hotter and droughts lasting longer, these traditionally wet regions are drying out, creating highly flammable tracts of dried-out peat. This makes fire one of the largest natural threats to a peatland. When a fire starts, it spreads down through the roots of the surface vegetation and into the peat layer. There it can burn uncontrolled—and difficult to reach—for months.

But even the threat of wildfire pales in comparison to what’s on the horizon. As the climate warms, peat long frozen under the tundra and boreal forests of the Arctic and subarctic zones is starting to thaw. University of Alberta researchers estimate that thawing peat could release approximately 232 billion metric tonnes of legacy greenhouse gases and carbon into the atmosphere over the next century. 

A glimmer of hope

Despite the bleak outlook, there is some hope for peat. In England, so many peatlands have been excavated and drained to help the country’s gardens grow that the sale of peat for use in the amateur horticulture sector will be banned by the end of 2024. Before the ban, the amount of peat sold annually in the UK could fill 29,000 shipping containers, according to the conservation charity Derbyshire Wildlife Trust. If the amount of peat used in the UK during 2020 alone had been left in the ground, it would have permanently stored approximately 238,000 metric tonnes of carbon. 

In Canada, harvesting practices are more sustainable. A global leader in horticultural peat production, the country is often accused of depleting peat resources for the sake of recreational gardening. But while peatlands cover 113.6 million hectares of land in Canada, less than 0.03% of that resource has been or is currently being harvested. 

Only sphagnum-moss peatlands with a peat thickness of 2 m or more and an area of 50 hectares or greater are harvested commercially. Almost every province and territory has strict regulations governing peat harvest. In New Brunswick, for example, a producer must have a plan to restore a harvested area before the government issues the necessary permit.

The Canadian Sphagnum Peat Moss Association (CSPMA)—an association of peat moss producers—was involved with developing the Responsibly Managed Peatlands Certification that is now maintained by international third-party certifier SCS Global Services. In 2022, the non-profit Ducks Unlimited—whose mission is to “conserve, restore, and manage wetlands”—signed a five-year memorandum of understanding to work collaboratively with the CSPMA in developing sustainable management practices. 

Wetland re-peat 

That sounds like great news for peat, but it may be the work of researchers such as Line Rochefort—director of the Peatland Ecological Research Group (PERG) at Laval University—that will ultimately change peat’s fortunes. I spoke with Rochefort this past winter. 

“Throughout the years, we have found several solutions to restore peatlands,” she told me during our phone conversation. PERG’s moss layer transplant technique (MLTT) starts by reintroducing plant species such as sphagnum mosses back into the landscape. The mosses serve as a source of plant spores, fragments, and other propagules that can establish and grow in the restored wetland. Within five years, 82% of the species present in the original shrub growth return; within 10 to 15 years, studies show, the annual carbon sequestration rate of a restored peatland is the same as before harvest. 

Another restoration practice is rewetting, which can take place as a part of MLTT or independently of it. Rewetting involves blocking the drainage ditches dug for harvesting, constructing dikes to stop water from draining out of the peatland, or completely flooding a previously harvested area. These actions help to restore hydrological conditions and restart the peat-formation process.

Protecting and restoring peatlands could reduce global greenhouse gas emissions by 800 million metric tonnes per year.

At Burns Bog, DeMill worked on behalf of the municipality of Delta to rewet the area, damming the ditches dug during peat excavation.“ There are 500 km of ditches, and I was damming every 100 m,” he says. Have his efforts made a difference? He hopes so. 

There is more hope for Burns Bog, too, as it begins to benefit from a growing global recognition of the value of peatlands. In 2007, after years of advocacy by groups such as the Burns Bog Conservation Society and the citizens of Delta, over 2,000 hectares in the centre of the bog were protected under an ecological covenant managed by the Metro Vancouver Regional District. The remaining 1,200 hectares on the fringes of the bog, however, continue to be at risk of drainage to make way for further development. And as DeMill has observed, draining even one portion of a peatland affects it all.

According to the United Nations Environment Programme, protecting and restoring peatlands and the peat they house could reduce global greenhouse gas emissions by 800 million metric tonnes per year. The next chapters in the story of peat will depend on the world coming to a clear understanding that peat is, indeed, a global air conditioner. Without it, we’re going to get hotter faster.