Global patterns of drought recovery

A global analysis of gross primary productivity reveals that drought recovery is driven by climate and carbon cycling, with recovery longest in the tropics and high northern latitudes, and with impacts increasing over the twentieth century. Droughts affect ecosystem carbon storage, but the factors influencing ecosystem recovery from droughts remain poorly understood. This study finds that gross primary productivity recovery times from droughts are strongly associated with climate and carbon cycle dynamics and to a much lesser extent with biodiversity and carbon dioxide fertilization. The authors find that recovery time is longest in the tropics and high northern latitudes. They also observe that the area of ecosystems under active recovery and the length of recovery time have increased globally over the twentieth century. If future droughts become more frequent this may lead to a chronic state of incomplete recovery with adverse consequences for the land carbon sink. Drought, a recurring phenomenon with major impacts on both human and natural systems1,2,3, is the most widespread climatic extreme that negatively affects the land carbon sink2,4. Although twentieth-century trends in drought regimes are ambiguous5,6,7, across many regions more frequent and severe droughts are expected in the twenty-first century3,7,8,9. Recovery time—how long an ecosystem requires to revert to its pre-drought functional state—is a critical metric of drought impact. Yet the factors influencing drought recovery and its spatiotemporal patterns at the global scale are largely unknown. Here we analyse three independent datasets of gross primary productivity and show that, across diverse ecosystems, drought recovery times are strongly associated with climate and carbon cycle dynamics, with biodiversity and CO2 fertilization as secondary factors. Our analysis also provides two key insights into the spatiotemporal patterns of drought recovery time: first, that recovery is longest in the tropics and high northern latitudes (both vulnerable areas of Earth’s climate system10) and second, that drought impacts11 (assessed using the area of ecosystems actively recovering and time to recovery) have increased over the twentieth century. If droughts become more frequent, as expected, the time between droughts may become shorter than drought recovery time, leading to permanently damaged ecosystems and widespread degradation of the land carbon sink.