Peatlands are waterlogged ecosystems where dead plant material accumulates faster than it decomposes, building up thick layers of organic soil called peat over thousands of years. They cover roughly 3% of the Earth’s land surface, yet they store around 600 gigatons of carbon in their soil, more than all the world’s forest biomass combined. That makes them one of the most important natural carbon reserves on the planet, even though most people have never heard of them.
How Peat Forms
The key ingredient is water. Peatlands stay permanently or near-permanently saturated, which starves the soil of oxygen. Without oxygen, bacteria and fungi can’t break down dead plants the way they normally would on dry land. Instead of fully decomposing, the plant material slowly compresses into dense, spongy layers of peat. This process is extraordinarily slow: peat typically accumulates at a rate of about a millimeter per year, meaning a meter-deep peat deposit represents roughly a thousand years of buildup.
Several factors influence how quickly (or slowly) this happens. The type of vegetation matters, as does the depth of the water table, the acidity of the water, and the balance between new organic material arriving and old material breaking down. In highly acidic, waterlogged conditions, decomposition slows to a crawl, and carbon that would otherwise return to the atmosphere as CO2 gets locked away in the ground instead.
Bogs vs. Fens: The Two Main Types
Not all peatlands work the same way. The two major categories are bogs and fens, and they differ primarily in where their water comes from.
- Bogs receive nearly all their water from rainfall. Because rain carries very few dissolved minerals, bogs are nutrient-poor and highly acidic. Sphagnum moss dominates these landscapes, and the moss itself actively increases acidity, creating conditions that further slow decomposition. Bogs tend to look like vast, treeless carpets of moss and low-growing shrubs.
- Fens receive water from groundwater and surrounding mineral soils in addition to rain. This extra input of dissolved nutrients makes fens less acidic and more productive. They support a wider variety of grasses, sedges, and wildflowers compared to the sparse vegetation of bogs.
Both types accumulate peat, but the chemistry of that peat differs. Bog peat is typically more acidic and decomposes even more slowly, while fen peat contains more mineral content from the groundwater that feeds it.
Where Peatlands Are Found
Peatlands exist on every continent, but they’re not evenly distributed. Asia holds the largest share at roughly 38% of global peatland area, followed by North America at about 32% and Europe at around 13%. South America accounts for nearly 12%, with Africa making up about 4%.
The popular image of peatlands as cold, northern landscapes is only partly right. Vast expanses of peat do stretch across Canada, Scandinavia, Russia, and Scotland. But tropical peatlands in Southeast Asia, the Amazon basin, and the Congo Basin are far more extensive than scientists initially realized. Older inventories likely underestimated tropical peat extent while overestimating it in some northern regions. The Congo Basin alone contains one of the largest tropical peatland complexes on Earth, discovered in detail only in 2017.
Carbon Storage and Climate
Healthy peatlands absorb roughly 0.37 gigatons of CO2 from the atmosphere each year, a greater rate of carbon storage than all other vegetation types in the world. Over millennia, this steady absorption has packed 600 gigatons of carbon into peat soils globally. To put that in perspective, burning all of that stored carbon would release more CO2 than is currently held in the biomass of every forest on the planet.
The flip side is alarming. When peatlands are drained for agriculture, forestry, or development, the waterlogged conditions that prevent decomposition disappear. Oxygen floods in, microbes wake up, and the ancient carbon starts breaking down. Degraded peatlands now emit an estimated 2 gigatons of CO2 equivalent per year (not counting fires), which amounts to about 5% of all human-caused greenhouse gas emissions. In tropical regions like Indonesia, drained peatlands are also highly flammable, and peat fires can burn underground for months, releasing enormous plumes of carbon and choking nearby cities with smoke.
Water Regulation and Flood Control
Peatlands function like massive natural sponges. Healthy peat soil can hold up to 20 times its dry weight in water, which means peatlands absorb heavy rainfall and release it slowly over time. This buffering effect reduces peak flows in rivers and streams downstream, lowering flood risk for communities in the surrounding area. Peatlands also accumulate roughly 70% of the world’s natural freshwater, making them critical reservoirs in many regions.
When peatlands are drained, they lose this sponge-like capacity. Water runs off quickly through ditches and channels, increasing the speed and volume of downstream flooding. Restoration efforts that block drainage ditches and rebuild natural barriers have been shown to raise and stabilize water tables, increase water storage in surface pools, and reduce peak storm flows. In practical terms, restoring a degraded peatland can meaningfully reduce downstream flood risk.
Wildlife and Biodiversity
Peatland ecosystems support species found nowhere else. Sphagnum mosses are the foundation of bog ecosystems, and their ability to acidify water and retain moisture creates a niche habitat that only specialized organisms can tolerate. Heather, sundews (carnivorous plants that trap insects to supplement the nutrient-poor soil), cranberries, and cotton grasses are all characteristic peatland plants.
The animal communities are equally distinctive. Specialist beetles adapted to acidic, waterlogged conditions are found almost exclusively in peatland habitats. Studies have identified groups of aquatic beetles that thrive only in acidic standing water, alongside ground-dwelling species tied to the mossy, shrubby terrain. Peatlands also serve as breeding grounds for wading birds, provide habitat for dragonflies and damselflies, and in tropical regions support species ranging from orangutans to freshwater fish found in peat-stained blackwater rivers.
Threats to Peatlands
Drainage is the single biggest threat. Around 500,000 square kilometers of peatland worldwide have been drained, primarily to create farmland, plant timber, or extract peat for fuel and horticulture. Once drained, peat soil shrinks, compacts, and oxidizes. Land that took millennia to build can lose meters of depth within decades. In some drained regions of Europe, land surfaces have dropped by several meters since drainage began.
Climate change compounds the problem. Rising temperatures accelerate decomposition even in undrained peatlands, and shifting rainfall patterns can lower water tables naturally. Permafrost peatlands in the Arctic are particularly vulnerable: as permafrost thaws, vast stores of frozen peat become exposed to decomposition for the first time in thousands of years.
Restoration and Global Targets
The primary method for restoring degraded peatlands is rewetting: blocking drainage ditches, building low barriers called bunds, and reshaping the landscape so water stays on the surface. When water tables rise again, decomposition slows and carbon loss drops significantly, sometimes stopping almost immediately. Over longer timeframes, rewetted peatlands can begin sequestering carbon again as new plant material accumulates.
Rewetting does come with caveats. Restored peatlands don’t simply revert to their pre-drainage state. Research shows that rewetted fens tend to be colonized by tall grasses and reeds rather than the original moss communities, and differences in vegetation, water chemistry, and soil structure can persist for decades or longer. The biodiversity of a restored peatland is typically different from, not identical to, what existed before drainage.
Internationally, momentum is building. The Peatland Breakthrough, a coalition led by Wetlands International, the UN Environment Programme, and the UN Food and Agriculture Organization, has set three targets: halt the loss of undrained peatlands by 2030, rewet at least 30 million hectares by 2030, and implement sustainable management across all peatlands by 2050. Meeting Paris Agreement climate goals would require rewetting roughly one million hectares of drained peatland per year, every year, until mid-century.
Economic Value
Putting a dollar figure on peatlands is difficult, but the numbers that do exist are striking. A study in Sumatra estimated the total economic value of peatland services at about $3,174 per household per year for communities living near them, roughly 1.3 times the average household income in the region. Carbon sequestration alone accounted for $509 per household annually, or 88% of the indirect use value. Water provision for agriculture and household use contributed another $122 combined. These figures don’t yet include harder-to-measure services like flood protection, pollination, and water purification, meaning the true economic value is almost certainly higher.