Deforestation effects on Amazon forest resilience

Through vegetation-atmosphere feedbacks, rainfall reductions as a result of Amazon deforestation could reduce the resilience on the remaining forest to perturbations and potentially lead to large-scale Amazon forest loss. We track observation-based water fluxes from sources (evapotranspiration) to sinks (rainfall) to assess the effect of deforestation on continental rainfall. By studying 21st century deforestation scenarios, we show that deforestation can reduce dry season rainfall by up to 20% far from the deforested area, namely, over the western Amazon basin and the La Plata basin. As a consequence, forest resilience is systematically eroded in the southwestern region covering a quarter of the current Amazon forest. Our findings suggest that the climatological effects of deforestation can lead to permanent forest loss in this region. We identify hot spot regions where forest loss should be avoided to maintain the ecological integrity of the Amazon forest. Plain Language Summary The Amazon forest is a giant water pump. It releases huge amount of water to the atmosphere by transpiration. This water is then recycled back as precipitation over the forest, sometimes in remote locations following large-scale transport in the atmosphere. We use an empirical approach based on satellite images to quantify changes in the water flux following 21st century deforestation scenarios. We find rainfall reductions by up to 20% downwind of the deforested area (western Amazon and subtropical South America). This in turn increases the ecological vulnerability of the remaining forest to perturbations (logging, fire, and extreme drought), in particular, in southwestern Amazonia. Our results suggest that increasing deforestation might lead to permanent forest loss in this region. We show that the regions where deforestation would most increase the ecological vulnerability of the whole forest coincide with regions likely to be deforested or degraded in the near future. Therefore, forest protection strategies should be defined to maintain the water pump, in order to avoid changes in rainfall over South America and to sustain the ecological integrity of the Amazon forest.