Oil spills and invasive species drive losses in Nigeria's mangrove forests.

Abstract

Mangrove forests are important organic carbon sinks and provide many ecosystem services. However, data on historic extent, biodiversity and carbon stocks remain scarce, especially in Nigeria, the country with the fifth-largest mangrove area globally. Here, we integrate field surveys, remote sensing data (from 40 years of Landsat satellite imagery, TanDEM-X InSAR, GEDI, high-resolution imagery, ALOS/PALSAR and Sentinel-1 synthetic aperture radar) and numerical modelling to assess changes in mangrove extent, the drivers of change as well as the impact on past and future carbon fluxes. We estimate a total mangrove area of 957 747 ha for 2023 and a 4.5% loss of Nigeria's total mangrove area from 1990 to 2023. By 2023, almost 10% of Nigeria's mangroves-93 178 ha-are dominated by the invasive mangrove palm, Nypa fruticans, which expanded by 70 000 ha in just 15 years. Oil spill pollution was the direct cause of at least 37% of all mangrove ecosystem loss and the main driver of loss in the Niger Delta. These findings indicate that Nigeria has experienced the third-largest loss of mangrove cover extent globally, after Indonesia and Australia. We found that the total cumulative emissions from mangrove conversion from 1995 to 2023 were 48.62 Tg CO2eq, equivalent to almost 40% of Nigeria's annual emissions in 2023. 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'.