Tropical deforestation causes large reductions in observed precipitation.

Tropical forests play a critical role in the hydrological cycle and can influence local and regional precipitation. Previous work has assessed the impacts of tropical deforestation on precipitation, but these efforts have been largely limited to case studies. A wider analysis of interactions between deforestation and precipitation-and especially how any such interactions might vary across spatial scales-is lacking. Here we show reduced precipitation over deforested regions across the tropics. Our results arise from a pan-tropical assessment of the impacts of 2003-2017 forest loss on precipitation using satellite, station-based and reanalysis datasets. The effect of deforestation on precipitation increased at larger scales, with satellite datasets showing that forest loss caused robust reductions in precipitation at scales greater than 50 km. The greatest declines in precipitation occurred at 200 km, the largest scale we explored, for which 1 percentage point of forest loss reduced precipitation by 0.25 ± 0.1 mm per month. Reanalysis and station-based products disagree on the direction of precipitation responses to forest loss, which we attribute to sparse in situ tropical measurements. We estimate that future deforestation in the Congo will reduce local precipitation by 8-10% in 2100. Our findings provide a compelling argument for tropical forest conservation to support regional climate resilience.