Between the 1930s and 1980s, Finland drained 4.7 million hectares of peatland to accelerate forest growth; the exposed peat soils are now a growing source of carbon dioxide

Imagine draining a wetland larger than the entire country of Switzerland. That’s basically what Finland did to its peat bogs in the mid-20th century. Research published in the journal Biogeosciences in 2023 found that 4.7 million hectares of peatland were drained for forestry in Finland, with the heaviest digging in the 1960s and 1970s. The study found that decades later, the soils have become a source of carbon dioxide rather than a carbon store.

For US millennials who grew up hearing about rainforests as the planet's "lungs," this might be a plot twist. It turns out that, acre for acre, peatlands are the world's most efficient natural carbon vaults, not rainforests. Finland just gave us a real-life case study of what happens when you drain one at scale.

Why Finland drained so much land
Peat bogs cover almost a third of Finland’s land surface. The push for drainage was driven in large part by practicality, according to NOAA’s Arctic Report Card 2023. Finland owed the Soviet Union war reparations after World War II, and timber exports were among the quickest ways to pay off that debt. Forestry became a national priority, and foresters dug millions of ditches to drain the wet soil so it would dry out and support faster-growing trees. The country still has in total 4.7 million hectares of drained peatland today, says the Natural Resources Institute Finland (Luke).


It worked, in the sense that trees grew. But peat is not ordinary soil. It is compressed, waterlogged plant matter that has locked away carbon for thousands of years. Drain it and expose it to air, and microbes start breaking it down, releasing carbon dioxide slowly but steadily, year after year.

The soil is now breathing out carbon
The Biogeosciences study, led by researchers at Luke, built a new model to track how much CO2 these drained soils actually release. The same Biogeosciences research found that across the 4.3 million hectares of drained peat that meet the official definition of forest land, annual soil emissions rose from around 1.4 million tons of CO2 in 1990 to almost 7.9 million tons in 2021. The study found that in the warmer and more populated southern half of the country, these forest ecosystems went from being a net carbon sink to a net carbon source in the early 2010s.

That flip is a big deal. What that means is that the trees growing on that drained land are no longer pulling down enough carbon to offset what the soil underneath is losing. The problem is the climate system itself.

And there’s the bigger picture. Peatlands cover a minuscule fraction of the Earth’s land surface, but contain more than 30 percent of the world’s remaining soil-based carbon, NOAA Arctic Report Card 2023 notes, citing the Intergovernmental Panel on Climate Change. Drain enough of them, anywhere in the world, and you can undermine broader climate goals and the communities that depend on them.

A blueprint for undoing the damage
There is also a more hopeful part of the story. Finland is not just watching this happen. A Finnish nonprofit, Snowchange Cooperative, has rewilded and restored about 52,000 hectares of degraded peatland and forest since 2017, working closely with Sámi Indigenous communities and local villages, according to NOAA’s Arctic Report Card 2023. The technique is simple: they block the old drainage ditches, causing the water table to rise and the mosses and wetland plants to reclaim the land.

The same NOAA report states that a former peat mining site in North Karelia has increased its support from four to six bird species before restoration to more than 200 bird species today, some of which are regionally rare. The river of the site, which was previously considered severely damaged, is now inhabited by a spawning population of a critically endangered brown trout.

That is a tiny fraction of the 4.7 million hectares that have been drained, but it shows the damage is not permanent. Rewetted peat stops releasing carbon and can slowly start storing it again.

What this means for the US
The US has peatlands of its own, from the pocosins of North Carolina to the great bogs of Alaska and Minnesota. The same drain-it-for-development instinct shaped much American land use in the 20th century as well. Finland’s experience is a preview of a bill that comes due decades later, quietly, as rising soil emissions nobody budgeted for.

It’s a useful reminder for a generation who already take climate change as background noise in every headline that the ground under our feet is not neutral. Either we lock up the carbon, or we let it go. Finland learned the hard way for decades, and now is spending real time and money to undo it, one blocked ditch at a time.