Satellite observations reveal a reversal trend in African woody cover around 2010

International audience African woody vegetation plays a crucial role in regulating tropical land carbon flux variability and is important for global climate mitigation. However, our knowledge of its long-term trajectories remains limited. Here, we combine microwave satellite observations from VODCA Vegetation Optical Depth (VOD) and l-VOD products to analyze the long-term trends in African woody cover during 1988–2020, and employ a Random Forest model to uncover the main drivers of woody cover dynamics. The VOD-derived woody cover estimates were evaluated against both multiple satellite-based woody cover products and independent field observations (R² = 0.60–0.83), indicating robust overall agreement. Based on this analysis, we estimate a reversal in the woody cover trend around 2010 over Africa in 40% of African woodland area, with a reduction in woody cover after 2010 offsetting approximately 32% of the gains observed before 2010. This reversal was particularly pronounced in southern Africa where woody cover trend shifted from a significant increases (1.6%·decade-1 (95%CI: 1.1%, 2.2%)) before 2010 to a significant decrease after 2010 (-1.4%·decade-1 (95%CI: -4.1%, 0.3%)). Land cover change is identified as the most influential factor in driving changes in woody cover, contributing 35.1% of the total importance, followed by vapor pressure deficit (VPD, 28.3%) and precipitation (9.2%). Earth system models from CMIP6 largely fail to capture both the temporal reversal point and spatial hotspots of woody cover trend reversal observed in our satellite-based analysis, indicating limited capability in reproducing recent changes in African woody vegetation. These findings provide observational evidence that, although woody plant encroachment and CO₂ fertilization driving increases in some dryland regions, these gains have been offset by significant regional-scale declines in woody cover that emerged around 2010 across parts of Africa. This spatial divergence challenges the previous consensus of a widespread and continuous increase in woody vegetation in this part of the world.