Quantifying and Understanding the Tropical Peatlands of the Central Congo Basin

The world’s second largest tropical wetland is found in the central Congo Basin. Ambiguous grey-literature reports of peat, coupled with the large area of wetland suggest this region may be a globally significant carbon store. In this thesis I aim to establish whether this region, known as the Cuvette Centrale, harbours significant peatlands, to characterise them, compute the first estimate of peatland extent and C stocks based on ground data, to determine the factors which led to peat initiation and their maintenance today. Fieldwork within the Likouala Department, Republic of Congo, confirmed widespread peat presence. Peat-vegetation associations were recorded in the field, which combined with remotely sensed radar, optical and elevation data was used to estimate the area of peatland; at 145,529 km2 (95% CI, 134,720-154,732 km2), the Cuvette Centrale is the single most extensive tropical peatland complex in the world. The peat is shallow (maximum depth: 5.90 m) and characterised as non-domed, nutrient poor systems, occupying large interfluvial basins. Area measurements combined with those of peat depth, bulk density and C concentration, collected in the field, suggest a total peat C stock of 30.2 Pg C (90% CI, 27.8-32.7 Pg C). This increases the current global tropical peatland C stock estimate from 88.6 Pg C to 115.8 Pg C. Radiocarbon dates show peat initiated early Holocene (dated from 10555 cal yrs BP onwards), with a possible Mid- to Late-Holocene hiatus in peat accumulation, with both likely linked to changes in regional precipitation. Pressure transducers measuring the peatland water tables, rainfall estimates and water source geochemistry imply that the peatlands today are predominantly rain-fed systems. My discovery that the Congo Basin, not tropical Asia, is home to the world’s largest single peatland complex elevates the current global peatland C stock estimate from 88.6 Pg C to 115.8 Pg C and will require new regional management plans if the destructive fate of tropical Asian peatlands are to be avoided in central Africa.