Rising CO₂ May Slow Expansion of Global Drylands, New Study Finds

Recent modeling work indicates that the way plants adjust to higher atmospheric carbon dioxide could act as a natural brake on the outward spread of dryland regions.

Drylands—areas where precipitation falls short of the amount needed to offset the atmosphere's capacity to extract moisture from soils and vegetation—have been flagged as one of the most vulnerable ecosystems in a warming world. Their boundaries are already shifting, prompting concern over impacts on food security, biodiversity and human livelihoods.

The study focuses on the so‑called CO₂ fertilisation effect, where elevated carbon levels improve photosynthetic efficiency and, crucially, reduce the amount of water plants lose through transpiration. By using satellite observations and process‑based climate models, researchers quantified how this enhanced water‑use efficiency could offset some of the moisture deficits that drive desertification.

Results show that, under a range of emission scenarios, the net gain in plant water savings could shrink the projected area of new drylands by up to several percent by mid‑century. The effect is strongest in regions where vegetation is already marginally water‑limited, such as parts of the Sahel, Central Asia and western North America.

While the findings do not suggest that rising CO₂ will halt desert expansion altogether, they highlight a feedback mechanism that could buy time for adaptation measures. Policymakers and land managers may need to account for this nuance when designing strategies to protect vulnerable populations and ecosystems.

Scientists caution that the benefit hinges on the persistence of other climate factors, including temperature rise and changes in precipitation patterns. Future research will aim to refine the interaction between CO₂‑driven plant responses and extreme weather events, which remain a major uncertainty in predicting dryland dynamics.