Multi-year droughts are becoming hotter, lasting longer and causing more damage: study

Alexandra Mae Jones · CBC News

· Posted: Jan 16, 2025 8:00 PM EST | Last Updated: 28 minutes ago

Droughts that stretch on for years at a time are becoming longer and more devastating for ecosystems across the globe, according to a new study.   

And in the wake of 2024 being declared the hottest year on record, it's raising questions about how prepared Canada is for what's to come. 

When an individual drought event has a huge impact on the environment or communities, it garners a lot of attention. But many droughts occur in regions with a low enough human population to go unreported, or in tropical or mountainous regions where the impacts aren't immediately detrimental or obvious, making it hard to get an accurate picture of the occurrence of drought. 

For this study, published in the peer-reviewed journal Science, researchers mapped out the global distribution of more than 13,000 multi-year droughts, which occurred from 1980 to 2018, to get that big-picture look. 

They found that multi-year droughts are becoming hotter, longer and more severe, and have occurred on nearly every continent. 

The land affected by multi-year droughts is increasing by nearly 50,000 square kilometres globally per year, according to the study.

"Which is more than the area of Switzerland," Dirk Karger, senior researcher at the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and senior author of the study, told CBC News. 

Researchers measured drought severity by looking at the balance of precipitation in a region versus how much water was lost to evaporation. They also used satellite images to measure changes in vegetation greenness, and found that grasslands are the most affected by drought conditions. 

Among the most severe events in recent decades were multi-year droughts in Mongolia, southeastern Australia and the western United States.  

'Tipping points'

Several of the multi-year droughts that researchers identified were ones that had gone overlooked in regions of the Andes and the Congo and Amazon rainforests.

Tracking these matters even if the individual impacts aren't immediately obvious or detrimental, Karger said, because multi-year droughts can lead to "tipping points" where the quality of soil and vegetation in an area has been so damaged that recovery is impossible, turning forests into savannahs and savannahs into deserts.