The Threat of Multi-Year Drought in Western Amazonia

Recent "once-in-a-century" Amazonian droughts highlight the impacts of drought and climate change on this region's vegetation, carbon storage, water cycling, biodiversity, land use, and economy. The latest climate model simulations suggest this region will experience worsening future drought. However, the instrumental record is too short to quantify the range of background drought variability, or to evaluate extended drought risk in climate models. To overcome these limitations, we generated a new, highly resolved lake record of hydroclimatic variability within the western Amazon Basin. We find that Amazonia has regularly experienced multi-year droughts over the last millennium. Our results indicate that current climate model simulations likely underestimate the background risk of multi-year Amazonian drought. These findings illustrate that the future sustainability of the Amazonian forest and its many services may require management strategies that consider the likelihood of multi-year droughts superimposed on a continued warming trend.