Aerial view of the peatlands in Odzala-Kokoua National Park, Cuvette-Ouest Region, Republic of the Congo. Credit: Education Images/Universal Images Group via Getty Images
The central Congo Basin, where 28% of the world’s tropical peat carbon is stored, releases carbon rapidly during drought conditions. This is of particular concern as droughts driven by anthropogenic carbon emissions may trigger a positive carbon cycle feedback, as the peatlands switch from storing carbon to releasing it into the atmosphere.
A study published in Nature, analysed organic matter properties, preserved pollen and hydrogen isotopes of plant waxes in core samples and found that drier conditions were associated with markedly reduced peat accumulation.
The findings showed that in the past, the negative outcome has been reversed when climatic conditions stabilize, allowing peatlands to recover and the accumulation of peat and the sequestration of carbon to be resumed.
Using peat cores from a large interfluvial basin in the Republic of the Congo and palaeoenvironmental research methods, a team led by Simon Lewis at the University of Leeds School of Geography, and colleagues, investigated the hydroclimatic vulnerability of the central Congo Basin’s store of nearly 30 billion metric tonnes of carbon in peat.
The team, including scientists at the Democratic Republic of Congo’s Marien Ngouabi University, University of Kisangani, and the Higher Pedagogical Institute of Mbandaka, [RD1] [RD2] reported that the peat that accumulated between around 7,500 to about 2,000 years ago is much more decomposed compared with older and younger peat.
“The data imply that the drying climate probably resulted in a regional drop in the water table, which triggered peat decomposition, including the loss of peat carbon accumulated prior to the onset of the drier conditions,” the team stated. But after about 2,000 years ago, they observed that the drying trend ceased, hydrologic conditions stabilized and peat accumulation resumed.
The researchers called for more investments in palaeoenvironmental research at other central Congo peatland sites, monitoring of both regional climate and contemporary peatland conditions, and predictive models of peatland carbon storage and release.
“These are needed to identify future peatland threshold behaviour and fully assess the susceptibility of these carbon dense ecosystems to 21st-century climate change,” they suggested.
Peat cores have provided evidence for climate and environmental change over the last 135,000 years, by facilitating precise dating that enables the estimation of past climate changes. The International Peatland Society (IPS) estimated that every climatic zone and continent has peatlands covering a combined area of more than 4 million km2, representing nearly 3% of the Earth’s terrestrial surface.
“Peatlands are carbon rich ecosystems that store and sequester more carbon than any other type of terrestrial ecosystem, exceeding even the global above-ground carbon stock of forest ecosystems,” IPS stated.
