The ‘idea’: Uncovering the peatlands of the Congo Basin

  • In 2017, a team of scientists from the U.K. and the Republic of Congo announced the discovery of a massive peatland the size of England in the Congo Basin.
  • Sometimes called the Cuvette Centrale, this peatland covers 145,529 square kilometers (56,189 square miles) in the northern Republic of Congo and the Democratic Republic of Congo, and holds about 20 times as much carbon as the U.S. releases from burning fossil fuels in a year.
  • Today, the Congo Basin peatlands are relatively intact while supporting nearby human communities and a variety of wildlife species, but threats in the form of agriculture, oil and gas exploration and logging loom on the horizon.
  • That has led scientists, conservationists and governments to look for ways to protect and better understand the peatlands for the benefit of the people and animals they support and the future of the global climate.

This is the first article in our four-part series “The Congo Basin peatlands.”

The notion seemed straightforward: A massive swamp in the Congo Basin relatively unknown to most of the world, apart from a few human communities and a bewildering array of wildlife, could be the ideal spot for a carbon-rich soil known as peat.

Simon Lewis, a plant ecologist who had scouted the region and spoken with scientists there, had a strong suspicion about what lay just beneath the surface of this part of the world’s second-largest rainforest. So he got to work bringing together a team of Congolese and British scientists, including a doctoral student at the time named Greta Dargie.

Early on, the team’s initial scans of satellite images looking at the topography, plant life and water dynamics in the area suggested this was a promising area for peat. The next step was to visit and plunge their tools into the earth in a series of make-or-break moments that would either prove the hunch correct or leave them with empty hands stained only with the dark soils of this remote swamp forest.

They left the forest anything but emptyhanded and have since returned again and again with a growing team to pull back the curtain on what makes tropical peatlands work. Today, the revelations have changed our calculus of how peat fits into the broader climate picture.

But it turned out just getting into the peatlands was anything but simple.

Confusion about the validity of papers led to the team’s short detention in Impfondo, the capital of the Republic of Congo’s Likouala department, before they were ultimately released. Once in the peatlands, they battled hip-deep sucking mud, sweltering temperatures and humidity-saturated air. They also had to balance such ironies as being surrounded by sopping swampland and having to glean fresh drinking water from wallows left behind by crocodiles.

If surviving on its own wasn’t hard enough, they had work to do, something that Dargie and Lewis say would not have been possible without the help of people from the communities in the area. On several trips between 2012 and 2014, their days-long transects covered 20-30 kilometers (12-19 miles) at a clip. The transects involved stops, sometimes every 250 meters (820 feet), to take core samples of the earth.

An aerial view of village in Lac Paku in the peatland forest near Mbandaka, Democratic Republic of the Congo. Image © Daniel Beltrá / Greenpeace.

Lewis, a professor at the U.K.’s University of Leeds and University College London as well as Dargie’s Ph.D. supervisor, said they operated only with “an idea” the expansive wetland might in fact be replete with peat.

Yet, “Everywhere we went, we found it,” Lewis said.

The evidence they pulled together confirmed this “peatland complex” is the most substantial in the tropics and was more than five times larger than scientists had previously supposed. Often referred to as the Cuvette Centrale peatlands for a province in the Republic of Congo that houses part of it, in reality, it covers a massive 145,529 square kilometers (56,189 square miles) — an area larger than England — that straddles the border with the neighboring Democratic Republic of Congo (DRC).

After the findings became public in Dargie’s dissertation in 2015 and later in a 2017 report in the journal Nature, the figures sent reverberations through the scientific community. And for good reason, Lewis said.

“It’s totally shocking,” Lewis, co-lead author with Dargie on the Nature paper, told Mongabay. “How can you have 145,000 square kilometers of peatland that have not been mapped before?”

What’s more, within this expansive peatland lies a repository below the surface of more than 30 billion metric tons of carbon, or around two-thirds of the amount held aboveground in all the trees across the entire Congo rainforest.

Almost immediately, the revelations touched off a firestorm of interest in the peatlands. It’s clear the peatlands are a vital part of the global carbon budget. But scientists now need to know how these peatlands formed, whether they’re uniform across their surface, and how they’ve responded to previous climate shocks — all questions that will help determine how securely the carbon remains locked away.

In the shorter term, concessions for oil and gas and logging cover much of the peatlands’ area in both countries. And the specter of agriculture for crops such as oil palm looms on the horizon, as producers turn their gaze from Southeast Asia to Africa for new lands to cultivate.

Today, the Cuvette Centrale appears pretty well intact. But researchers say tinkering with the hydrodynamics of its peatlands, by building roads, for example, or by draining them completely to make them suitable for agriculture, could spell disaster for the stored carbon.

“I think we will only protect what is valued,” Lewis said, “and we need to know where these peatlands are because they are such huge stores of carbon so that they’re not accidentally converted and inadvertently release huge amounts of carbon into the atmosphere.”

Satellite image of the Congo Basin peatlands in the Democratic Republic of the Congo. Image via Microsoft Zoom Earth.

An unknown quantity

In most tropical forests, the decomposition process begins almost as soon as leaves, branches and other natural detritus hit the ground. Immediately, insects, bacteria and fungi start tearing them apart, kicking off rapid decay aided by the hot, humid climate. One of the byproducts of this process is carbon, freshly unshackled from the once-living organic matter so abundant in rainforests.

In the swampy areas where peat forms, however, the soil is so saturated with water that dead bits of plants don’t break down as quickly. Waterlogging, Lewis said, leads to “this buildup of carbon, of this semi-decomposed plant matter that we call peat.” So instead of going back into the atmosphere, it’s effectively tied up due to this arrested decay.

Over time — we’re talking millennia — the peat builds up, layer upon layer. Scientists figure that the Cuvette Centrale peatlands started forming around 10,600 years ago, though parts of it may be even older.

“You think a 400-year-old forest is old, and then you start touching soil,” said Julie Loisel, an assistant professor and ecosystem scientist at Texas A&M University who studies peatlands around the world but wasn’t involved in the Cuvette Centrale research. “That’s 10,000 years old.”

Before the team started taking core samples in the Cuvette Centrale in 2012, little was known about what lay underfoot, at least from a scientific standpoint.

“There were some … very sketchy numbers,” said Susan Page, a professor and ecologist at the University of Leicester and co-author of the 2017 Nature paper. Scientists knew that a gargantuan wetland spilled over the borders of the two Congos, but they didn’t know how much peat it might contain. Earlier estimates were much smaller than the England-size area the team ended up finding.

A Greenpeace campaigner holding peat in the forest around Mbandaka, Democratic Republic of the Congo. Image © Daniel Beltrá / Greenpeace.

In the late 2000s, Lewis had been working to understand the carbon held aboveground in the forests of the Congo Basin. But the wetlands in the northern Republic of Congo piqued his interest. On a visit to Brazzaville, the country’s capital, he decided to see if he could find local scientists to work with on a project there.

In this part of Africa, the great Congo River arcs its way through the region’s forests. Second only to the Amazon in the volume of water it shuttles from the interior of the Congo Basin to the Atlantic Ocean, it meanders and sloshes down a slope of only 115 meters (377 feet) along its entire 1,740-km (1,081-mi) length. The relatively gentle angle created by this pitch provides ample opportunity for water to break free of the river’s banks and invade the surrounding forest, setting up at least a possibility that peat might have been forming in this part of the world for some time.

“Simon basically said, ‘I think it might be quite peaty in the middle of the Congo Basin,’” said Ian Lawson, a co-author of the 2017 Nature paper and senior lecturer and paleoecologist at the University of St. Andrews in Scotland. Soon enough, Lewis had convinced Lawson to join the project.

Aerial view of Monboyo River and peatland forest of Salonga National Park in the Democratic Republic of the Congo. Image © Daniel Beltrá / Greenpeace.

The first satellite images the team looked at were also strikingly similar to known peatland areas in Indonesia and the Peruvian Amazon, said Edward Mitchard, another collaborator on the 2017 paper and a professor of global mapping at the University of Edinburgh. Information gathered with radar used to distinguish between forests that were flooded and those that were not, along with satellite sensors tuned to the presence of swamp-loving plants, suggested the marshy environs could be cradling peat.

So Lewis began designing a project to figure out if indeed the Cuvette Centrale contained peat. The aim was also to put some numbers to the extent, depth and carbon content of the peat, if it did in fact exist there. In 2017, the same year the scientific discovery of the peatlands came out, Lewis and a growing group of scientists from around the world created CongoPeat, a five-year research project aimed at digging into the science and policy implications of such a large peatland in the Congo Basin.

In a sense, the discovery of this carbon storehouse was akin to finding an immense buried treasure. But it’s the sort of treasure that’s only valuable if it stays underground. Fiddle too much with the processes that soak the soil and hold off decomposition, and that value — to the world’s future climate, at least — evaporates with the carbon seeping into the atmosphere.

One of the starkest examples of the consequences of the transition from carbon sink to source has happened over the past few decades in Southeast Asia. As in many parts of the world, farmers there traditionally burn forested land to clear it for agriculture. But because of peat’s high carbon content, dried-out peat burns very well. It even smolders underground, making peatland fires difficult to snuff out. That was the case in 2015 when fires linked to peatland conversion in Indonesia spread out of control, blanketing Southeast Asia in noxious smoke that scientists estimate led to the premature deaths of more than 100,000 people.

Burning peat doesn’t just release deadly particulates, however. To save pristine peat deposits, combat conversion and restore once-healthy peatlands, Indonesia, the Republic of Congo and the DRC came together to form to the Global Peatlands Initiative aimed at saving the world’s peatlands. According to the initiative, areas of peat that have been drained or burned release 2 billion metric tons of CO2 into the atmosphere every year, which works out to about 5% of all human-related emissions, also known as the global carbon budget.

“Greenhouse gas (GHG) emissions caused by peatland degradation [have] become the major carbon source in many peat-rich countries,” Jiren Xu, a research associate at Scotland’s University of Glasgow, said in an email to Mongabay.

In the Cuvette Centrale, the climate-warming potential of all of its stored carbon is dormant for the moment. But if that switch is flipped — if the water holding decay in check is drained away, or rising temperatures cause it to evaporate — it could be very difficult to turn off. The peatlands themselves would transform quickly from being one of the world’s most important reservoirs of carbon to a source that could contribute to climatic warming on a massive scale.

A team from Greenpeace Africa works with local partners to conduct scientific research in the village of Lokolama in the Democratic Republic of Congo. Image © Kevin McElvaney / Greenpeace.

Protection factor

In lockstep with the research coming out about the peatlands has been a push to find ways to protect them. One of the most visible moves was the signing of the Brazzaville Declaration in 2018, which brought together Indonesia, the Republic of Congo and the DRC in a call for tropical peatland conservation. The aim was “to protect the benefits provided by peatland ecosystems,” according to the United Nations Environment Programme (UNEP), by drawing on Indonesia’s experience in the realm.

It wasn’t the first effort to protect the area, according to Lera Miles, a principal specialist with UNEP’s World Conservation Management Centre and a member of the CongoPeat team.

“Well before the peatlands extent was realized and the Brazzaville Declaration was signed, both the DRC and the Republic of Congo had already declared very substantial national protected areas and Ramsar sites covering large areas of this forest,” Miles told Mongabay in an email. “The peatland carbon stocks only emphasize how important it is to protect it — it was already recognized as a critical wildlife habitat.”

The Ramsar Convention is an international agreement signed in 1971 that identifies key wetlands, not all of which contain peat, in the hopes of protecting them and the ecosystem services they provide.

International organizations like the U. N. have encouraged financing mechanisms aimed at promoting both economic development and conservation through approaches such as REDD+ (short for reducing emissions from deforestation and forest degradation) and the Green Climate Fund. Companies have also shown interest in paying to protect wetlands as a way to offset their own carbon emissions.

It’s unclear whether these solutions will provide enough support in the way of compensation to stave off the temptation to develop the Cuvette Centrale peatlands or extract the resources they contain. Indonesia’s own economic rise has come in part from draining some of its peatlands and planting them with in-demand crops like oil palm.

“It is true after all that, since the resources in peatlands and forests are not global public goods but are subject to state sovereignty, we would be perfectly legitimate in converting them into mining, agricultural or extractive activities, in order to boost our development,” said Arlette Soudan-Nonault, the Republic of Congo’s minister of the environment, sustainable development and the Congo Basin, in an email to Mongabay. “That is exactly what industrialized countries have done to boost theirs.”

One of the most visible moves to protect the peatlands was the signing of the Brazzaville Declaration in 2018, which brought together Indonesia, the Republic of Congo and the Democratic Republic of Congo in a call for tropical peatland conservation. Image courtesy of the Global Peatlands Initiative.

Scientists and conservation groups have rallied around the need to support the DRC and the Republic of Congo, and to do so sooner rather than later.

“We should do everything we possibly can to support the two Congos to protect those peatlands,” Page said, “because globally, they matter.”

Soudan-Nonault echoed that sentiment, calling on “the rich and polluting countries … to build a common agenda with us by supporting our conservation efforts in a concrete way.”

In some ways, the situation seems primed for effective protection and conservation, in part because of how remote, sparsely populated and intact the peatlands still are. Lewis said he sees that as both an opportunity and a warning.

“If we can’t develop ways to keep all that carbon locked up and keep all that biodiversity and improve the lives and livelihoods and incomes of the pretty small number of people who live there, then we can’t do it anywhere,” he said. “Everything is in the right configuration to do something really impressive and really good in the central Congo.”

The superlative stores of carbon contained in the Cuvette Centrale peatlands have dominated much of the discussion around the landscape’s value, and perhaps for good reason. Along with being the largest tropical peatland complex, they also contain 20 times the amount of carbon that the U.S. — the world’s second-biggest emitter — releases into the atmosphere from burning fossil fuels annually.

The peatlands’ “ancient carbon,” as Susan Page calls it, increases the known stockpile of tropical peatland carbon by more than a third, bringing the total to 105 billion metric tons worldwide. These areas are incredibly carbon-dense, especially considering that they cover only 3% of all land on Earth. And they represent an epoch’s worth of accumulation, which began around the start of the Holocene nearly 12,000 years ago.

“This long-term formation makes tropical peatland become one of the most important carbon stores in the world,” said Xu, who wasn’t involved in research for the 2017 Nature paper.

It also amplifies the importance of the DRC and the Republic of Congo, which now rank as the tropical countries with the second- and third-largest repositories, respectively, of peat in the world, after Indonesia.

But the value of the peatlands of the Cuvette Centrale extends aboveground as well.

The area is home to a wide array of wildlife, thanks in part to its remote location. Western lowland gorillas (Gorilla gorilla gorilla) and forest elephants (Loxodonta cyclotis), both listed as critically endangered by the IUCN, inhabit the area, as does one of our closest living relatives, the endangered bonobo (Pan paniscus).

“It’s one of the most intact and remote ecosystems on Earth,” Mitchard said.

These forests shelter long-standing human communities too, having provided them with fish, firewood and game for hundreds, if not thousands, of years. The area remains sparsely populated to this day, though, which is a key reason these peatlands are relatively undisturbed compared to those in Southeast Asia.

“The fact that they’re so remote is important,” Ian Lawson said. “It makes them kind of like natural nature reserves.”

A western lowland gorilla (Gorilla gorilla gorilla). The peatland-rich Cuvette Centrale area is home to a wide array of wildlife, including western lowland gorillas, forest elephants, and bonobos. Image by Wade Tregaskis via Flickr (CC BY-NC 2.0).

Creeping threats

How long the peatlands of the Cuvette Centrale will continue to act as a sanctuary for wildlife, people and carbon hinges both on finding out more about them and on dealing with a complicated set of factors that could mete out their destruction.

Just accessing the peatlands isn’t easy, as Dargie, now a research fellow at the University of Leeds, and her colleagues attest. Few roads connect the region to more populated areas. And once you’re there, traveling through hectare upon hectare of saturated swampland requires either a boat or a lot of patience. Such hurdles have kept the Cuvette Centrale peatlands mostly pristine until now. But it’s not clear how long the barriers to entry will outweigh the potential benefits to be had from turning over the peatlands to seemingly more lucrative purposes.

In the past few years, both countries have shown interest in tapping into the oil and gas that may lie below the peat, offering concessions to companies for tender. (Fossil fuels are themselves stockpiles of especially ancient carbon. But oil and gas deposits are millions of years older than peat, and their presence stems from a different set of processes than what leads to peat formation.)

In late 2019, two oil companies operating in the Republic of Congo announced the discovery of a pool of oil under the peatlands that was so large, it could nearly quadruple the country’s output, already the third-largest oil producer in sub-Saharan Africa. Experts immediately cast doubt on those claims, arguing that they were probably exaggerated, and questions swirled around the cost of extracting oil and gas from such a far-flung location. Still, the country’s hydrocarbons ministry continues to list five available oil concessions in its portion of the peatland complex, which have been connected to large multinationals like France’s Total and Italy’s ENI.

Neither Total nor ENI responded to repeated requests for comment.

Scientists say we need more information to understand how oil and gas extraction could affect peat. Indeed, that’s a line of research that Lewis and his colleagues are already pursuing. Proponents, and even some researchers, say techniques typically associated with offshore drilling involving helicopters and “floating” platforms that obviate the need for roads could minimize the impacts of extraction.

“I think you can save a peatland and get the oil out from way underneath it,” said Katherine Roucoux, a senior lecturer at the University of St. Andrews and a paleoecologist whose work centers on the peatlands of the Amazon. But she pointed out the cross purposes involved in trying to safeguard the peat’s carbon while extracting oil and gas that would ultimately add more of it to the atmosphere.

“I mean, the irony is just so deep. It obviously shouldn’t be done,” Roucoux added. “It’s a ridiculous thing.”

The swamp that makes the Cuvette Centrale possible, pictured here in the Democratic Republic of Congo. Image © Kevin McElvaney / Greenpeace.

Another unknown is the problem of oil spills. Again, scientists aren’t sure how that would impact the hydrodynamics of peatlands, though evidence from peatlands in the Amazon suggests they could be destructive, especially to human communities in the area.

In a win for environmental groups, authorities in the DRC recently removed concessions that overlapped with Salonga National Park, a sanctuary for bonobos and other wildlife that holds part of the peatlands. Other concessions tendered in 2018 remain in place, however.

Timber concessions have also been gridded out over the peatlands, and a recent move by the DRC government to end a long-standing moratorium on new timber concessions riled many conservation and civil society organizations. According to maps by Greenpeace, most of the peatlands in fact are covered by logging or oil and gas concessions, or both. Scientists and environmental organizations including Greenpeace and Rainforest Foundation UK have raised concerns that logging would damage the forests in the Cuvette Centrale and, as a result, the peatlands themselves.

Agriculture, too, could prove a temptation for leaders looking boost economies by leveraging the vast peatlands. Oil palm, which grows on former peatlands in parts of Indonesia and Malaysia, has come to drive the economies of those countries. But in those places, the peatlands have switched from being carbon sinks to sources.

“My big fear is that it goes down the route of Southeast Asia,” Lewis said. “We’ve already seen the kind of dystopian trajectory of taking peatlands, draining them, converting to oil palm plantations or fast-growing timber plantations, and then the out-of-control fires that come with the dry season … and all the environmental and climate and health problems that flow from that.”

The road construction necessary to get goods out of the peatlands, whether timber, agricultural produce, or fossil fuels, also worries Simon Lewis and other scientists.

“It can change the drainage over huge areas, and of course these are highly sensitive systems to the water availability,” Lewis said. “That can have huge impacts. I’ve seen evidence in the Republic of Congo where a road built for a logging company over an area of peatland changed the drainage completely and killed the vegetation for at least 30 kilometers.”

Such losses would have repercussions that reverberate both above and below ground in the peatlands.

Still, cordoning off the peatlands from development and protecting them for the wildlife and communities that call them home might not be enough to keep them from the kind of disruption that could turn on the carbon spigot.

An illustration of the environmental and social effects of peatland drainage. Image by Nieves Lopez Izquierdo/GRID-Arendal via Flickr (CC BY-NC-SA 2.0).

Even if immediate protection efforts are successful, it’s possible that climate change may push them down a path in which they begin emitting carbon. To persist over centuries and millennia, peatlands need to have a source of water that’s more or less consistent. Basically, they have to maintain what scientists call “a positive water balance.” The Congo River and its tributaries likely play a role in this balance as they wend their way through the Cuvette Centrale and occasionally creep beyond their banks to invade the forest.

But it seems likely, according to Dargie and her colleagues, that rainfall plays the primary role in making sure there’s more water flowing into the Congo Basin peatlands than flows out or evaporates off. That reliance on precipitation may place them on something of a knife’s edge, since they get quite a bit less rain compared to other peatlands in Southeast Asia and the Amazon. Peatlands in the Indonesian province of Central Kalimantan, on the island of Borneo, receive around 2,900 millimeters (114 inches) per year. On average, 3,000 mm (118 in) of rain falls on Peru’s Pastaza-Marañón complex, the largest peatland in the Amazon. In contrast, the peatlands of the Congo Basin only get around 1,700 mm (67 in).

Climate change is already having substantial effects on weather, which vary from region to region, and scientists working with the Intergovernmental Panel on Climate Change (IPCC) expect those impacts to intensify throughout the 21st century, according to a recent report.

But what exactly the direct repercussions of a warmer Earth will be for the Congo peatlands are hard to tease apart, Lewis said.

The dynamics are complex. In theory, more carbon in the atmosphere could boost plant growth, goading along the accumulation of more peat. But higher temperatures could also speed up the evaporation of water from the peatlands, creating an environment that’s more conducive to carbon-releasing decomposition. Scientists also expect — and to some degree, are already observing — sweeping shifts in weather patterns as a result of climate change. These variable effects could drench previously dry areas of the planet in the future while leaving once-rain-soaked regions thirsting for moisture.

“The big wild card is what happens to the seasonality of rainfall,” Lewis said. “Does that elongate or not?”

He said that at what point during the year rain falls on the peatlands and how long it lasts could be as important as the quantity that ends up soaking the soil. If, for example, the rainiest season of the year contracts, it could hasten the peatland’s demise, even if the total amount of rainfall hovers around that 1,700-mm average.

Lewis and his colleagues are working to piece together what keeps the peat going and how it has responded to past climate aberrations, as well as to model how it might respond to future shocks. Right now, the scientists say it’s too soon to tell, calling for an all-of-the-above strategy when it comes to the peatlands’ protection.

The reality is that even if local communities, national governments and international bodies like the U.N. come together to shore up protections for the Congo Basin peatlands and sidestep conversion to logging operations, oil fields or oil palm plantations, it may be that climate change has the ultimate say.

“Are they going to continue to put down carbon in the soil for us as a climate-cooling agent, or will they start spitting it out really quickly if we degrade them?” said Texas A&M’s Loisel.

It’s a critical question that Lewis and his colleagues are looking to answer as soon as they can.

“I suspect that it might not take that much to push them into being a carbon source,” he said. “But really I have to emphasize that we just don’t know at this stage and that’s what we’re doing in the field at the moment … so we can understand what are the main drivers of keeping the carbon locked up.

“Then we’ll have a better handle on what might happen in the future,” he added.

Listen to Mongabay’s podcast episode on peatland restoration here:

Banner image: Congo Basin Experts from the UK and DRC takes first samples from the Peatland. Image © Kevin McElvaney / Greenpeace.

John Cannon is a staff features writer with Mongabay. Find him on Twitter: @johnccannon


Dargie, G. C., Lewis, S. L., Lawson, I. T., Mitchard, E. T., Page, S. E., Bocko, Y. E., & Ifo, S. A. (2017). Age, extent and carbon storage of the central Congo Basin peatland complex. Nature, 542(7639), 86-90. doi:10.1038/nature21048

Correction: An earlier version of this article contained a map of Central Africa in which the peatlands were incorrectly identified. The identified areas were actually wetlands, not peatlands.

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