New study reveals Congo swamps as the world’s largest tropical peatland

Posted by ap507 at Jan 12, 2017 09:52 AM |
University of Leicester involved in new research mapping vast peatland in Congo Basin for the first time

Issued by University of Leicester Press Office on 12 January 2017

Images from the project are available here: https://drive.google.com/drive/folders/0B691WmQZab8LYnc1SjVuZ1Zacjg

A vast peatland in the Congo Basin has been mapped for the first time, revealing it to be largest in the tropics. 

The new study, which involved researchers from the University of Leicester, found the Cuvette Centrale peatlands in the central Congo Basin cover 145,500 square kilometres – an area larger than England. They lock in 30 billion tonnes of carbon making the region one of the most carbon-dense ecosystems on Earth.

The UK-Congolese research team spent three years exploring remote tropical swamp forests to find samples of peat for laboratory analysis. Their research, published today in Nature, combined the peat analysis with satellite imagery to estimate that the Congo Basin peatlands store the equivalent to three years of the world’s total fossil fuel emissions.

Researchers Professor Simon Lewis and Dr Greta Dargie from Leeds’ School of Geography and University College London, who co-led the study, first discovered the peatlands’ existence during fieldwork in 2012.

Professor Lewis said: “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. The peat covers only 4 per cent of the whole Congo Basin, but stores the same amount of carbon belowground as that stored aboveground in the trees covering the other 96 per cent.

“These peatlands hold nearly 30 per cent of the world’s tropical peatland carbon, that’s about 20 years of the fossil fuel emissions of the United States of America.”

Dr Dargie said: “Our 2012 discovery of the Congo Basin peat gave us just enough insight to refine our searches. It was in 2014 when we found the deepest peat deposits in the most remote areas of swamp that we 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. It is astonishing that discoveries like this can still be made.”

Professor Lewis added: “Our new peatland map is the first step in understanding this vast ecosystem. These swamp forests have been wrongly classified in all previous maps due to their remoteness and inaccessibility. I hope our work encourages much more investment in this neglected region to better understand the role of peatlands within the global carbon cycle and climate system.”

Peat is organic wetland soil made from part-decomposed plant debris. Healthy peatlands act as carbon sinks, removing carbon from the atmosphere through plant growth. Further decomposition of the peat is prevented by its waterlogged environment, locking up carbon.

But when peatlands dry out, either through changes in land use such as drainage for agriculture or reduced rainfall, further decomposition resumes, releasing carbon dioxide into the atmosphere.

Professor Lewis said: “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. Carbon has been building up in peat in the region for nearly 11,000 years.

“If the Congo Basin peatland complex was to be destroyed, this would release billions of tonnes of CO2 into our atmosphere.”

Professor Susan Page from the Department of Geography, University of Leicester, who co-led the study, added: “Tropical peatland is one of Earth’s largest and most efficient carbon sinks. Development of tropical peatland for agriculture and plantations removes the carbon sink capacity of the peatland system with large carbon losses arising particularly from enhanced peat degradation and the loss of any future carbon sequestration by the native peat swamp forest vegetation.” 

The study places the Democratic Republic of Congo (DRC) and the Republic of Congo (RoC) as the second and third most important countries in the world for tropical peat carbon stocks. In first place is Indonesia, as it contains the tropical peatlands across the islands of, Borneo, Sumatra and New Guinea.

But, as Professor Page explains: “Tropical peatlands in Indonesia are a globally important store of soil carbon but they are under enormous pressure from plantation and other forms of agricultural development which is leading to very high emissions of carbon dioxide, a greenhouse gas, into the atmosphere.”

Because of their remote location, the peatlands in the Congo Basin are relatively undisturbed. But they could face threats from drainage for agricultural plantations, particularly for palm oil, as is happening in Indonesia.

Because the Congolese peatlands are so newly-discovered, they do not feature in conservation plans to ensure they remain undisturbed.

The peat may also be vulnerable to the effects of climate change in two ways, if rising temperatures increase evaporation, or if average rainfall is reduced, to a point when the peat begins to dry out. At this point the peat would begin to release its carbon to the atmosphere.

Study co-author Dr Ifo Suspense, from the Université Marien Ngouabi in the RoC capital Brazzaville, said: “The discovery of the Cuvette Centrale peatlands could have a huge impact on the climate and conservation policies of the Congo. The maintenance and protection of this peatland complex could be the Congo’s great contribution to the global climate change problem.

“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.”

In addition to their importance to the global carbon stocks, the Congo Basin swamps are refuges for endangered species including lowland gorillas and forest elephants.

Dr Emma Stokes, Director of the Central Africa Program of the Wildlife Conservation Society said: “This research highlights the immense significance of these swamp forests for the stability of our climate. However, these forests, in the geographical heart of Africa, are also a vital refuge for many thousands of great apes, elephants and other large forest mammals that are threatened by developments in the surrounding landscape.  

“The RoC government is considering the expansion of Lac Tele Community Reserve, a move that could safeguard an additional 50,000 square kilometres of swamp forest – much of it overlying peat – from future disturbance.

“We strongly support this move and commend the RoC government for this initiative. We urge both countries to continue efforts to protect these habitats from industrial transformation.”

Dr Greta Dargie said: “With so many of the world’s tropical peatlands under threat from land development and the need to reduce carbon emissions to zero over the coming decades, it is essential that the Congo Basin peatlands remain intact. The combined effort of UK and Congolese researchers to determine the extent of the Congo Basin peatlands has been incredible. Conservation will also ensure that research into this unique region can continue.”  

The researchers used core samples to confirm the presence of peat soil and determine its maximum depth. The average depth was 2.4 metres but at its deepest, it went down 5.9 metres – roughly the height of a two-storey building.

The study used field data identifying peat presence and the vegetation that overlies it to determine that only two specific forest types have peat underneath: a year-round waterlogged swamp of hardwood trees and a year-round waterlogged swamp dominated by one species of palm tree.

The researchers then used data from US and Japanese satellites to map the two specific peat swamp forest types across the whole region to determine the boundaries of the Congo Basin peatlands. About 40% of the total extent of all the Cuvette Centrale wetlands has peat underneath. Combining this area with peat depth and peat carbon content from the laboratory analyses allowed the total carbon stocks to be calculated. The Cuvette Centrale peatland carbon stock estimate is 10 times higher than the previously published estimate.

Further information

Images:

For more information contact Professor Sue Page at the University of Leicester on email sep5@le.ac.uk

The research paper, "Age, extent, and carbon storage of the central Congo Basin peatland complex" is published in Nature on 11 January 2017 (DOI 10.1038/nature21048)

The discovery of the Cuvette Centrale peatlands was made possible by a Philip Leverhulme Prize to Professor Simon Lewis.

Dr Greta Dargie’s PhD and the radiocarbon dates were funded by the Natural Environment Research Council

Satellite image analysis was performed at the University of Edinburgh in collaboration with Dr Edward Mitchard, funded by the Natural Environment Research Council

Satellite image data was provided by the USGS, NASA and JAXA, and partially processed by OSFAC in Kinshasa, DRC.

For interviews, or video footage of the peatland please contact the University of Leeds press office via a.martinez@leeds.ac.uk

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