Damaging megadroughts are spreading across the world

(Bloomberg) — Severe drought has fueled wildfires in Los Angeles. But a new study, published Thursday in the journal Nature, comes with a warning: Climate change is making catastrophic, multi-year “megadroughts” around the world much worse.

Droughts are relative: for example, a drought in normally rainy Seattle might register as an unusually wet spell in a drier climate like Phoenix, Arizona. But they can disrupt ecosystems, sometimes in dangerous ways.

“That is what we are seeing now in California,” said Dirk Nikolaus Karger, senior researcher at the Swiss Federal Institute WSL and author of an article. “Over time, vegetation dries out, increasing the frequency of fires and burning down houses. In other areas we will face agricultural failures.”

California's fires are caused by just eight months of little rainfall. While climate change is contributing to more erratic precipitation in the western US, the new paper provides a global view of the droughts that have occurred in recent years. The researchers were motivated to do this after Karger and co-author Francesca Pellicciotti spent time in Chile in the midst of the drought that began in 2010.

“The consequences were devastating, from ecosystems to agriculture,” said Pellicciotti, professor at the Institute of Science and Technology Austria. The drought has led to periodic water rationing, including in Santiago, the country's capital, and disruptions in mining, a key part of the Chilean economy. In 2021 and 2022, Antofagasta, the London-based Chilean multinational, said it was forced to cut production due to the drought. In September, Google said it was halting plans to build a large data center due to water problems.

To find out how many other places have experienced similar megadroughts, researchers looked at precipitation and vegetation data. They also looked at spatial data to see how much impact the droughts had on the area.

They found that megadroughts have affected every continent except Antarctica over the past four decades. Mongolia, southeastern Australia and the western US were among the regions with the highest density of severe, multi-year droughts. However, the longest drought in their study was one in the eastern Congo Basin, which lasted ten years. It covered 576,924 square miles (1,494,226 square kilometers), an area about twice the size of Texas.

The researchers also found that climate change is causing an increase in areas where there are multi-year droughts.

“The extent to which these droughts increase in area per year is roughly the size of Switzerland,” said Liangzhi Chen, postdoctoral researcher at the Swiss Federal Institute WSL and lead author of the study.

As megadroughts expand their reach, so does the damage they can cause. Globally, droughts cause five times as many people to migrate than floods. According to a World Bank analysis, dry spells are responsible for saving more than half a percent on GDP in low- and middle-income countries. And as the climate warms, the problem is likely to get worse.

. stories like this are available at bloomberg.com