Atmospheric disconnection from the Amazon forests behind extreme droughts in a tropical savanna of the Orinoco basin

Abstract In 2014, an extreme drought caused massive, unprecedented livestock and wildlife deaths in northwestern South America’s tropical savanna region. The causes of this drought remain unclear. Here, we present evidence that a weakening of the atmospheric teleconnection from the Amazon forests is a previously unknown mechanism behind this and other regional droughts over the last decades. To quantify this weakening, we introduce the concept of ‘forest fraction anomaly’ (FFA) based on how the dominant patterns of atmospheric moisture transport pass over the forests. By combining climate records with FFAs computed for 1979–2019, we identify a decadal shift in the severity of droughts that coincides with an increasing weakening of the forest-savanna connection. Our results reveal a physically plausible mechanism linking the Amazon forests with the occurrence of droughts in neighboring savannas and provide an analytical framework for investigating forest-related droughts elsewhere.