Potential for improved groundwater recharge and dry-season flows through forest landscape restoration on degraded lands in the tropics

As interest in tropical forest restoration accelerates, understanding its hydrological implications is increasingly urgent. While concerns persist that reforestation will reduce annual water yields—particularly in drier climates—we highlight conditions under which forest landscape restoration (FLR) can improve seasonal water availability, especially during the dry season. We examine the trade-off between increased vegetation water use ("pumping") and enhanced infiltration and subsurface retention ("sponging") following forestation of degraded lands, the recovery of vegetation's ability to capture "occult" precipitation (fog) in specific coastal and montane settings, and the role of forest cover in enhancing moisture recycling and transport at multiple scales. A pantropical sensitivity analysis shows that in degraded landscapes with deep soils and pronounced rainfall seasonality, infiltration gains following forestation can offset or exceed evaporative losses, thereby supporting groundwater recharge and increasing dry-season flows in approximately 10% of cases, with an additional 8% showing near-neutral (slightly negative) outcomes. These findings challenge the assumption that forestation uniformly reduces water availability and underscore the need to prioritize dry-season flow recovery—rather than annual water yield—as a central hydrological goal of FLR. We call for trans-disciplinary research and long-term monitoring to inform forest restoration strategies, particularly in seasonally dry regions where water scarcity is most acute.