A probabilistic map of tropical peatlands in the Angolan Highlands Water Tower

Abstract

Peatlands provide critical ecosystem services, including habitat for biodiversity, water purification and climate regulation. Tropical peatlands in Africa present significant knowledge gaps in occurrence and extent estimates, and there is a lack of policy initiatives related to conservation and sustainable management. This study expands on a previous peatland extent estimate for the Angolan Highlands by extending the geographic scope to include the Angolan Highlands Water Tower (AHWT). We identified 51 ground-verified peat locations, using a peat corer, in multiple areas of the region during 5 separate field expeditions conducted between 2019 and 2023. These locations were used to independently evaluate an unsupervised classification model. The model incorporates satellite-derived vegetation and moisture indices (NDVI, NDWI), vegetation stress indices and terrain-based variables (including the Topographic Position Index) that capture key controls on peat formation in the AHWT. We generated a probabilistic map of potential peatland occurrence, estimating that peatlands cover between 8662 km2 (high certainty) and 11 167 km2 (low certainty), or 2.28–2.94% of the AHWT. The map was evaluated against field observations: all 51 ground-verified peat locations fell within areas predicted to have at least 50% peat probability (mean = 85.7%, s.d. = 20.4%). The resulting map offers a baseline for future field validation, carbon stock assessment and conservation planning. A French translation of this abstract is available in the supplementary material.

This article is part of the discussion meeting issue ‘African tropical peatlands: function, value and vulnerability’.