Full Breakdown
Projected Rise of Global Drylands and the Counteracting Role of CO2
9/8/2026, 11:24:33 PM
Study Overview and Projected Expansion
A 2026 paper in *Environmental Research Letters* estimates that drylands—areas where precipitation is low relative to potential evapotranspiration—could cover up to 40.28 percent of Earth’s land surface during the 2071–2100 period. This represents an increase of roughly 2.37 million km² compared with the 1994–2023 baseline, an area comparable to Algeria or about 30 percent of Australia.
Modeling Approach and CO2-Modified PET
The research team, led by scientists from the Chinese Academy of Forestry, applied an aridity-index (AI) threshold of 0.65 to define drylands. Their analysis incorporated historical meteorological records (1960–2023) and climate projections from the sixth phase of the Coupled Model Intercomparison Project (CMIP6). Crucially, the model adjusted potential evapotranspiration (PET) for rising atmospheric CO2, reflecting the tendency of plant stomata to close under higher CO2 concentrations. The authors note that conventional projections often omit this CO2 effect, which can inflate aridity estimates and shift hotspot patterns.
Regional Distribution and Subtype Shifts
Based on the 1994–2023 baseline, drylands presently occupy about 38.58 percent of global land (excluding Antarctica). Semi-arid zones constitute the largest share at 14.72 percent, followed by arid zones (11.24 percent, primarily in Australia and China), dry sub-humid zones (6.35 percent, concentrated in China and Russia), and hyper-arid zones (6.27 percent) found in Algeria, Libya, and Saudi Arabia. Projections indicate that hyper-arid areas will experience the greatest relative growth, while overall dryland coverage will rise to between 39.31 and 40.28 percent depending on the emissions scenario.
Significance for Ecosystems and Sustainable Development
The expansion of dryland climatic conditions threatens water availability, ecosystem integrity, and desertification processes, posing challenges to global sustainable-development goals. The study underscores the ecological vulnerability of drylands and calls for updated assessments to guide climate-adaptation strategies.
Future Outlook
The authors advocate for broader adoption of CO2-adjusted PET calculations in climate modeling to improve the accuracy of aridity forecasts. Continued monitoring and refined projections are needed to inform policy responses aimed at mitigating water scarcity and preserving vulnerable ecosystems as the planet warms.
