Angolan highlands peatlands: Extent, age and growth dynamics

• Published in: The Science of the total environment 2022-03, Vol.810, p.152315-152315, Article 152315
• Main Authors: Lourenco, Mauro, Fitchett, Jennifer M., Woodborne, Stephan
• Format: Article
• Language: English
• Subjects: Carbon; Carbon Cycle; Carbon storage; Climate Change; Ecosystem; Google Earth Engine; Normalised Difference Vegetation Index; Okavango; Radiocarbon; Remote sensing; Soil
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.152315

The Angolan highlands are hydrologically and ecologically important, supporting peatland deposits. Peatlands are carbon rich ecosystems and are the largest terrestrial carbon store. We present a first estimate of the extent of peatlands in the Angolan Highlands, using Google Earth Engine. Our conservative estimate of peatland coverage is 1634 km2, 2.65% of a mapped area spanning approximately 61,590 km2. This is a crucial first step in providing the peatland carbon inventory for the region and to facilitate conservation and management strategies. We include the peatland characteristics with respect to topographic data and common remote sensing indices of Normalised Difference Vegetation Index and Normalised Difference Water Index. The results suggest that Angolan Highlands peatland is highly variable in terms of elevation, slope, vegetation cover and standing water occurrence. Radiocarbon dating of riparian peatlands suggest two stages of peatland initiation: one about 7100 cal. yr BP, during the African humid period, and another from about 1100 cal. yr BP to present after the African humid period ended. The temporal control of riparian peat formation is river dynamics and the formation of terraces. Source lake peatland is slightly younger and has average maximum age of 890 cal. yr BP. The Angolan Highlands ecosystem and peatlands are possibly under strain from anthropogenic influence and climate change, making this peatland deposit a potential carbon emission source. The first map of the Angolan Highlands peatlands. An estimated peatland area of 1632 km2 is derived from the overlap of the Landsat 8 and Sentinel 2 random forest classifications. [Display omitted] •First peatland map in the Angolan Highlands using Google Earth Engine.•The peatland extent in Angola is much larger than previously estimated.•The peatlands have formed in lake environments, river floodplains and terraces.•The African Humid Period could be linked is as a driver of peatland initiation.•These previously unrecognised peatlands are under anthropogenic pressure.