A new study shows that while drylands are greening, they are also experiencing extreme year-to-year volatility that threatens agricultural and rangeland stability.

A study published in Nature Climate Change reports that global drylands are becoming increasingly unstable due to a 'boom-and-bust' cycle of vegetation growth. Researchers at the University of Arizona analyzed 40 years of satellite data, finding that while rising carbon dioxide levels have led to a persistent greening trend, this masks severe fluctuations in plant productivity. These swings leave ecosystems more vulnerable during dry years and present significant challenges for rain-fed agriculture and livestock management.

Escalating Volatility and Model Failures

The research team found that approximately 80% of global drylands are experiencing this escalating instability. While plants grow more during wet years due to increased water-use efficiency from higher atmospheric carbon dioxide, they become more sensitive to drought because their larger structures require more resources than are available during dry periods. The study evaluated 13 leading global vegetation models and discovered that none of them accurately captured this increase in year-to-year variability, as they currently assume dryland systems remain stable.

Impact on Agriculture and Rangelands

The unpredictability of plant growth poses direct risks to human livelihoods, particularly in regions like the American Southwest. For ranchers, the volatility in forage production makes it difficult to plan land use for each growing season. Researchers suggest that this 'flickering' effect in productivity may serve as an early warning sign that dryland ecosystems are losing their resilience and approaching a significant ecological shift.