The Cuvette Central. Image: Simon Lewis

A newly-discovered peatland in the Congo Basin of central Africa contains an estimated 30.6 billion tons of carbon in its waterlogged soils—equivalent to three times the total annual carbon emissions of every human being alive today.

Covering an area the size of England, the Cuvette Central is the largest tropical peatland area on Earth, dramatically increasing the amount of carbon stored in our planet’s hot and humid midsection, according to an analysis published last week in Nature. Now that this vast carbon sink has been identified, experts say we need to take every action possible to ensure it remains in the ground.

“Peatlands are only a resource in the fight against climate change when left intact, and so maintaining large stores of carbon in undisturbed peatlands should be a priority,” lead study author Simon Lewis said in a statement. “Our new results show that carbon has been building up in the Congo Basin’s peat for nearly 11,000 years.”

A simplified map of the Cuvette Central, with pink indicating peat swamp, yellow indicating savannah, and green indicating other tropical forest. Image: Simon Lewis

Peatlands only cover about three percent of Earth’s land surface, but they contain up to a third of all of the carbon sequestered in soils. Peat forms in waterlogged regions where plants add lots of organic material to the soil, but where decomposition is inhibited by a lack of oxygen (and, in the case of boreal and tundra peatlands, low temperatures). Over time, the highly organic, dark brown-to-black muck soils that characterize peatlands can compress into coal. That is, unless the soil warms up and dries out, at which point all of that carbon is liable to escape back to the atmosphere.

Vast peatlands underlie forests in western Amazonia and Indonesia, but until recently, nobody knew whether the world’s third major tropical forest region—the Congo Basin of Central Africa—also contained significant deposits of carbon-rich muck. But ecologists Greta Dargie and Simon Lewis of the University of Leeds suspected that we might find peat if we looked for it, particularly in a wet, topographically-depressed region of the Congo’s interior, known as the Cuvette Central.

Peat in the Cuvette Central. Image: Simon Lewis

To do so, the researchers conducted an extensive, three year field campaign, sampling soils within a remote area of the northern Republic of Congo (ROC) spanning 15,400 square miles (40,000 square kilometers). Combining field measurements with satellite remote sensing data on elevation and soil moisture, the researchers identified a vast peat layer underlying 56,000 square miles (145,000 square kilometers) of swamp forest and averaging nearly 8 feet (2.5 meters) deep. Radiocarbon dating indicates that the peat started accumulating 10,600 years ago, coincident with the onset of the Holocene epoch, which brought humid conditions to central Africa.

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All told, Cuvette Central is thought to be the most extensive peatland ever identified in the tropics, hoarding some 30.6 billion tons of carbon in just 4 percent of the Congo basin. That’s roughly the same amount of carbon stored in all of the above-ground vegetation across the other 96 percent of the basin. It’s also equivalent to about 20 years of fossil fuel emissions in the United States, or three years of human carbon emissions globally.

“The sheer expanse of these peatlands makes central Africa home to the world’s most extensive peatland complex,” Dargie said in a statement. “It is astonishing that in 2016 discoveries like this can still be made.”

Other large tropical peatlands, on the islands of New Guinea, Bornea and Sumatra, have shrunk substantially in recent years due to land use changes, including drainage for agriculture and human-caused wildfires. When peatlands burn, they’re like carbon bombs, releasing tremendous plumes of climate-warming greenhouse gases into the atmosphere. (In October of 2015, Indonesian peatland fires were briefly emitting as much CO2 as the entire US economy.)

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Unlike the imperiled peatlands of south Asia, most of the Cuvette Central remains untouched. This could change, the researchers say, if swift action is not taken to protect these forests, which also happens to be a last refuge for famous African megafauna including lowland gorillas and forest elephants. Threats to the Cuvette Central include future drainage for agriculture and a reduction in rainfall due to climate change, which may already be happening.

As it stands, peatlands in the ROC and the neighboring Democratic Republic of Congo could, if maintained, represent a significant carbon offset for the entire African continent, whose human population and carbon footprint are projected to soar in the decades to come.

“The existence of such large and previously unquantified components of the national carbon stocks of both ROC and DRC,” the researchers write, “provides an additional imperative...to work with the people of the Cuvette Centrale to pursue development pathways that will radically improve local livelihoods and welfare without compromising the integrity of this globally significant region of Earth.”

[Nature]