Global patterns of drought recovery

Drought has major impacts on natural and human systems1-3, and is especially important for land carbon sink variability due to its influence on terrestrial biosphere climate regulation4. While 20th Century trends in drought regimes have been varied5, and conclusions about both historical and projected changes in drought are index-dependent*, “more extreme extremes”6, including more frequent and severe droughts in some regions3,7, are expected in the 21st Century. Recovery time, the length of time 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 are largely unknown. Here we use three independent global data products of gross primary productivity to show that, across diverse terrestrial 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: (1) Across the globe, recovery is longest in the tropics and high northern latitudes—critical tipping elements in Earth’s climate system8. (2) Drought impacts9, assessed as the area of ecosystems under active recovery and recovery times, have increased over the 20th century. If future droughts become more frequent, time between droughts may become shorter than drought recovery time, leading to chronically impacted ecosystems.