The forest loss within small reservoirs surpasses that of large reservoirs across the tropics

The vast potential of hydropower remains crucial in addressing the escalating need for clean energy, particularly in Tropical Moist Forests (TMFs) regions. Yet, the widespread construction of reservoirs within TMFs has resulted in the inundation of forested areas, exacerbating the fragmentation of forest landscapes and contributing additional loss of carbon stored in these ecosystems. Despite this, the scale and degree of forest loss within reservoirs due to inundation from reservoir construction remain poorly quantified and mapped across tropical regions. Here, we leverage long-term TMFs data spanning from 1990 to 2021 to investigate forest loss within reservoirs across tropical regions. We reveal that forest losses within reservoirs total 3521 km2, constituting a relatively small fraction of total forest loss. Nonetheless, the spatial distribution of forest loss within reservoirs varies significantly across the tropics, with patchy distributions observed in the American and African TMFs, and striped patterns evident in the Asian TMFs. Contrary to common assumptions, we show that small reservoirs exhibit higher levels of forest loss compared to large reservoirs, particularly pronounced in the African TMFs region. Furthermore, our projections indicate that the exclusive construction of small reservoirs contributes to approximately 27% of Africa’s total forest area lost. We underscore the importance of policymakers carefully evaluating the trade-offs associated with the construction of large versus small reservoirs in TMF regions, to minimize the adverse impacts of hydropower development on forest ecosystems.