A groundbreaking study published in Science has revealed that megadroughts severe, long-lasting dry spells have been increasing in size, duration, and intensity over the past four decades. Researchers found that the total land area affected by multiyear droughts has expanded by 50,000 square kilometers (12 million acres) annually, signaling an alarming trend driven by climate change.
A Comprehensive Global Drought Catalog
For the first time, scientists have compiled a global catalog of long-term drought events since 1980, assessing their effects on vegetation and ranking their severity. The research, led by Liangzhi Chen of the Swiss Federal Institute for Forest, Snow, and Landscape Research WSL, identified 13,176 individual droughts lasting longer than two years between 1980 and 2018.
“We found that megadroughts are becoming more frequent and severe worldwide,” said Pascal Buri, a glaciologist at the University of Alaska Fairbanks and one of the study’s authors.
To analyze these events, researchers used the Standardized Precipitation Evapotranspiration Index (SPEI) to measure changes in precipitation and water loss, alongside high-resolution satellite data from the Landsat Normalized Difference Vegetation Index (NDVI) to track vegetation response.
The Rising Toll of Multiyear Droughts
The study underscores the devastating impact of prolonged droughts on ecosystems and water resources. Even short-lived droughts can damage plant life and water reserves, but prolonged events disrupt entire landscapes. In mountainous regions such as Chile, which has faced persistent drought since 2010, decreasing snowfall and glacial melt threaten the long-term viability of water reservoirs.
“At some point, if these droughts continue, the system will break vegetation will die, and aquifers will not be replenished,” warned Francesca Pellicciotti, a glaciologist at the Institute of Science and Technology Austria and co-author of the study.
Megadroughts have left lasting scars on regions such as the western United States (2008-2014), Australia (2017-2019), and Mongolia (2000-2011). However, lesser-known droughts, like the 2010-2018 dry spell in the Congo Basin, have also significantly affected tropical ecosystems, covering an area half the size of Alaska.
Ranking the Most Severe Megadroughts
By analyzing spatial extent, duration, and precipitation anomalies, researchers ranked the world’s most severe megadroughts. The top-ranking event was the 2008-2014 drought in southwestern North America, while other prolonged events, such as Chile’s 15-year drought, ranked lower due to their relatively smaller geographic impact.
Different landscapes responded uniquely to drought stress. Grasslands exhibited the most significant vegetation decline, whereas tropical forests appeared more resistant to prolonged dryness, though their long-term resilience remains uncertain.
Implications for Future Climate Policy
With megadroughts projected to intensify in the coming years, scientists emphasize the urgent need for mitigation and adaptation strategies. Policymakers can use this newly developed drought catalog to improve water management, conservation efforts, and emergency preparedness.
“The 2020s are already among the hottest years on record, and we expect continued changes in drought patterns,” said Pellicciotti. “This study should open new avenues for research into how different ecosystems recover from prolonged drought conditions.”
As climate change continues to disrupt global weather patterns, understanding and addressing the growing threat of megadroughts is essential for sustaining water security, agriculture, and ecosystems worldwide.