CLIMATE MATTERS: American Southwest drylands face escalating instability, study shows

TUCSON, Ariz. — More than 80% of global drylands are experiencing escalating instability that could threaten agriculture and livestock rangelands. A study published in Nature Climate Change reveals that rising carbon dioxide levels are creating a volatile “boom-and-bust” cycle in these ecosystems.

The study analyzed more than 40 years of satellite data. University of Arizona researchers discovered that while increased carbon dioxide stimulates plant growth during wet years, it leaves ecosystems highly vulnerable to severe crashes during dry years. This volatility is not captured by major global vegetation models, which overestimate dryland stability.

The findings have significant implications for rain-fed farming regions like the American Southwest. Increased year-to-year volatility may force farmers to rely more heavily on artificial irrigation, while making pasture forage production highly unpredictable for ranchers.

“The upper and lower extremes are getting farther and farther apart as time goes by,” Wen Zhang, a doctoral student who led the research team, said. “Vegetation activity is increasing during wet years, but dry years are hitting plants harder.”

Scientists warn this “flickering” of productivity could be an early warning sign of a major ecological collapse, indicating that drylands are losing their resilience, officials said. The research team evaluated 13 leading global vegetation models and found that none accounted for this increasing year-to-year variability.

Researchers hope the findings will inspire new studies focused on a better understanding and representation of drylands in the global climate system.