From the American West to eastern China, more than three-quarters of Earth’s land became persistently drier in recent decades, according to a new United Nations report that called the shift a “global, existential peril.”
Industrial emissions of planet-warming gases were a major culprit, the report said. If nations don’t stop the rise in temperatures, the drying is likely to expose more places to sand and dust storms, wildfires, water shortages, crop failures and desertification.
The report was released on Monday at a U.N. summit taking place this month in Riyadh, Saudi Arabia, where nations are discussing how to stop more habitable surfaces from turning into barren wastelands.
Nearly one in three people live in moisture-deprived areas, up from one in five in 1990, the report said.
Many of these places are major food producers, such as Argentina, Spain and the Black Sea region, said Narcisa Pricope, one of the report’s authors and a land systems scientist at Mississippi State University. Others, like South Sudan, are vulnerable to conflict and political instability.
The aridity crisis is unfolding “in our lifetime,” Dr. Pricope said. “This is affecting our children.”
Worldwide in recent years, nearly 400,000 square miles of the planet’s healthy and productive land has become degraded annually. Under the 30-year-old U.N. Convention to Combat Desertification, countries committed themselves to halting the devastation.
The desertification summit is the first major U.N. conference to be hosted by Saudi Arabia, home to one of the largest deserts on Earth. But as the world’s top exporter of oil, the nation has sought to slow global efforts to address climate change and environmental harms.
At U.N. climate talks in Azerbaijan last month, Saudi officials worked to undermine a commitment to move away from fossil fuels, negotiators said, even though Saudi Arabia was one of nearly 200 nations that endorsed the pledge last year. Saudi delegates also led a successful effort in South Korea to block a deal to limit plastic pollution and production.
The report released on Monday outlined actions that could increase societies’ resilience, including rethinking where thirsty crops like wheat and alfalfa are grown. Places with long histories of water challenges — Los Angeles, for instance — are already exploring such shifts, said Barron Orr, the lead scientist for the U.N. Convention to Combat Desertification.
“I’m not saying it’s easy, but at least they know how to do it,” Dr. Orr said. “That’s not going to be true for many very large urban areas all over the world.”
Places that scientists classify as drylands don’t just face the occasional drought. They are persistently moisture-deficient: Much more water leaves the ground through evaporation and the release of vapor by plants than arrives as rain or snow.
As of 2020, more than 40 percent of Earth’s land outside Antarctica was considered dryland, the U.N. report found. How much more land goes dry this century depends on how much fossil fuel societies continue burning, the report said.
“As long as we are continuing to warm the atmosphere, the atmosphere basically demands more water,” Dr. Pricope said.
Europe is especially vulnerable, the report found. More than 95 percent of the continent’s land has become drier in recent decades, and this trend could intensify if emissions rise to very high levels.
Some dry areas could become wetter as the planet grows hotter, the report found, including parts of Central Africa and India. With a warmer atmosphere, rain and snow can fall in heavier bursts, which in certain regions could help to offset the increased drying from higher temperatures.
Yet nowhere that’s classified as dryland today is projected to become persistently humid in the coming decades, the report said.
The environmental consequences of the drying trend can’t always be reversed, at least not on human time scales, said Peter Greve, a water and climate scientist at Helmholtz-Zentrum Hereon, a research institute in Germany.
“In these drylands, many of the ecosystems are super adapted to the current conditions,” Dr. Greve said.
It’s tempting to think plants and other organisms could simply adapt to warmer conditions by shifting northward or into higher altitudes, he said. “But sometimes it’s just not possible,” he added, “because the changes are too fast.”
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