Wetland Expansion Reduces CO2 ‐Equivalent Emissions and Strengthens the Congo Basin's Role as a Net Carbon Sink

TL;DR

Wetland expansion in the Congo Basin has increased its role as a carbon sink despite rising methane emissions.

Contribution

Quantified wetland expansion and its impact on CO2-equivalent emissions in the Congo Basin using satellite data.

Findings

Swamp forests expanded by 14% between 2007 and 2024, reversing prior drying trends.

Wetland expansion reduced CO2-equivalent emissions by 2 million tonnes per year since 2007.

Increased productivity in both swamp and terra firme forests was observed with wetting trends.

Abstract

Wetlands are the largest natural source of methane, yet their desiccation releases substantial amounts of carbon dioxide. Changing wetland emissions provide the greatest source of uncertainty in global emissions estimates due to limited data for key tropical carbon sources and sinks, including the Congo Basin. Here we quantified changing swamp forest hydrology, forest productivity and greenhouse gas emissions between 2007 and 2024 using satellite Earth observation and emissions datasets. We show that swamp forests expanded from 195,345 km2 to 222,467 km2 between 2007 and 2024, demonstrating a reversal of previously reported long‐term drying trends. The observed wetting trend increased productivity in both swamp and terra firme forests. Despite increasing methane emissions, wetland expansion reduced CO2‐equivalent emissions by 2 (95% CI; −2.94 to −1.12) million tonnes per year since 2007, highlighting the region's increasing role as a net carbon sink and its significance for global carbon budgets.

Congo Basin peat swamp forests are vital carbon sinks, yet climate‐driven shifts in hydrology and wetland greenhouse gas fluxes have not been assessed. Here we quantified changes in swamp forest extents, water table levels, forest productivity and wetland greenhouse gas fluxes between 2007 and 2024. Contrary to previously reported long‐term drying trends, we found that swamp forests expanded by 14%. Despite increasing methane emissions, wetland expansion reduced CO2‐equivalent emissions by 2 million tonnes per year since 2007. Our findings highlight the Congo Basin's increasing role as a net carbon sink and its significance for global carbon budgets.

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