Intensifying droughts may be pushing tropical forests toward a dangerous threshold
The study, published in Geophysical Research Letters, analyzed nearly four decades of satellite observations and climate records spanning tropical regions in South America, Africa and Southeast Asia. Dr. Shuai Cheng, from China's Eastern Institute of Technology, and colleagues found that drought affecting tropical vegetation has increased steadily since the early 1980s, with some of the strongest trends appearing in African tropical forests.
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Rather than relying solely on rainfall records, the researchers developed a method designed to capture how vegetation itself responds to drought conditions. Using long-term satellite measurements of plant activity alongside climate data from 1982 to 2019, they identified periods when tropical vegetation showed signs of physiological stress caused by both low soil moisture and dry air.
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The study found that these combined stresses are intensifying across much of the tropics. More than half of the increase in vegetation droughts was linked to declining soil moisture driven largely by warming temperatures and increased atmospheric drying. Africa experienced the strongest expansion in drought-affected vegetation, although significant increases were also observed in the Amazon and Southeast Asia.
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Healthy, undisturbed forests are generally better able to withstand drought than fragmented landscapes weakened by logging, agriculture or fire. The findings add to growing evidence that climate change is not only affecting tropical forests in isolated events, but is altering the background conditions these ecosystems rely on to survive and whether they can continue performing that role in a hotter, drier world remains one of the biggest unanswered questions in climate science.