Conservation news

World’s largest tropical peatlands discovered in swamp forests of Congo Basin

  • The peatlands, which weren’t even known to exist as recently as five years ago, were revealed to cover 145,500 square kilometres (or more than 17,500 square miles), an area larger than England, and to sequester some 30 billion metric tons of carbon.
  • That makes them one of the most carbon-rich ecosystems on Earth, according to the researchers who made the discovery and subsequently mapped the peatlands.
  • Professor Simon Lewis and Dr. Greta Dargie, who are both affiliated with the University of Leeds and University College London, first discovered the peatlands’ existence while doing fieldwork in the region in 2012.

A vast area of peatlands in the swamp forests of the Congo Basin, known as the Cuvette Centrale peatlands, has just been mapped for the first time and shown to be the largest in all of the tropics.

The peatlands, which weren’t even known to exist as recently as five years ago, were revealed to cover 145,500 square kilometers (or more than 56,000 square miles), an area larger than England, and to sequester some 30 billion metric tons of carbon. That makes them one of the most carbon-rich ecosystems on Earth, as well, according to the researchers who made the discovery and subsequently mapped the peatlands.

Professor Simon Lewis and Dr. Greta Dargie, who are both affiliated with the University of Leeds and University College London in the UK, first discovered the peatlands’ existence while doing fieldwork in the region in 2012. Lewis and Dargie were also the co-lead authors of a study published in the journal Nature earlier this month that details their use of core samples to determine the presence and depth of peat soil in the region.

The average depth of the Cuvette Centrale peatlands was found to be 2.4 meters (about 7.9 feet), but at its deepest the peat soil reaches 5.9 meters (a little over 19 feet), roughly the height of a two-story building.

“Our 2012 discovery of the Congo Basin peat gave us just enough insight to refine our searches,” Dargie said in a statement. But it wasn’t until 2014, when they found the deepest peat deposits in the most remote swamp forests, that they realized the importance of the Cuvette Centrale peatlands.

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

A peat bog in the Cuvette Centrale. Photo by Professor Simon Lewis, University of Leeds.

Lewis, Dargie, and their research team found that just two forest types in the Congo Basin have peat underneath: a year-round waterlogged swamp of hardwood trees and a year-round waterlogged swamp dominated by a single species of palm. They used data from US and Japanese satellites to map the two peat swamp forest types across the entire region in order to establish the boundaries of the peatlands.

The Cuvette Centrale wetlands occupy about 10 percent of the Congo Basin, and about 40 percent of the total extent of all the Cuvette Centrale wetlands has peat underneath, according to the researchers.

“Our research shows that the peat in the central Congo Basin covers a colossal amount of land. It is 16 times larger than the previous estimate and is the single largest peatland complex found anywhere in the tropics,” Lewis said in a statement. “We have also found 30 billion tonnes of carbon that nobody knew existed. The peat covers only 4 per cent of the whole Congo Basin, but stores the same amount of carbon below ground as that stored above ground in the trees covering the other 96 per cent.”

Peat is an organic wetland soil that is made of partly decomposed plant debris. Further decomposition of peat is inhibited by its waterlogged environment. Healthy peatlands are carbon sinks, meaning they store carbon that was removed from the atmosphere by the growth of plants. Remaining waterlogged year-round is necessary for peat to form in the tropics. If peatlands dry out, whether due to changes in land use or reduced rainfall, decomposition resumes, releasing carbon dioxide into the atmosphere.

Peat is also vulnerable to the effects of climate change, through both rising temperatures that increase evaporation and reduced average rainfall, which can cause peat to dry out and release its carbon.

The study suggests that the Democratic Republic of the Congo (DRC) and the Republic of the Congo (RoC) contain some of the most important tropical peat carbon stocks. The swamp forests of the DRC and the RoC are also home to the endangered western lowland gorilla (Gorilla gorilla gorilla) and the African forest elephant (Loxodonta cyclotis).

Indonesia, which hosts tropical peatlands across the islands of Borneo, Sumatra and New Guinea, is perhaps the only country that is more important in terms of peat carbon. In total, Indonesia has lost 94,000 square kilometers (or more than 36,000 square miles) of peatland, mostly due to fires and drainage canals that are used to convert the land for agricultural operations, the authors of the Nature study note.

Indonesia’s newly created Peatland Restoration Agency, which was established specifically to prevent a recurrence of the devastating forest and peatland fires that occurred in 2015, has called for all peat domes in the country to be designated as protected areas.

The peatlands in the Congo Basin are, as yet, relatively undisturbed, thanks largely to their remote location. But Lewis, Dargie, and their co-authors warn that they could soon face threats of drainage for agricultural plantations, particularly oil palm plantations, just as has occurred in Indonesia in recent years.

Because the Cuvette Centrale peatlands were discovered so recently, they are not included in current conservation plans for the region. During last year’s UN climate talks in Marrakesh, Morocco, however, seven African nations, including the DRC and the RoC, pledged to protect their tropical forests by shifting to sustainable palm oil production.

“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,” Lewis said. “Our new results show that carbon has been building up in the Congo Basin’s peat for nearly 11,000 years. If the Congo Basin peatland complex was to be destroyed, this would release billions of tonnes of carbon dioxide into our atmosphere.”

Dr. Ifo Suspense of the Université Marien Ngouabi in the RoC, a co-author of the Nature study, argued that the discovery of the Cuvette Centrale peatlands should feature prominently in climate and conservation policies governing the Congo Basin.

“The maintenance and protection of this peatland complex, alongside protecting our forests, could be central Africa’s great contribution to the global climate change problem,” Suspense said. “It is of the utmost importance that governments, conservation and scientific communities work with the people of the Cuvette Centrale to improve local livelihoods without compromising the integrity of this globally significant region of Earth.”

A young lowland gorilla in Gabon. The swamp forests of the DRC and the RoC are home to the endangered western lowland gorilla (Gorilla gorilla gorilla). Photo by Rhett Butler.

CITATION

Correction: this article originally stated the peatlands “covered 145,500 square kilometers (or more than 17,500 square miles)”. The proper figure was 56,000 square miles.