Dry and arid regions could cover more than 40 percent of Earth's land surface, excluding Antarctica, by the end of the 21st century, according to a study published in the journal Environmental Research Letters (ERL).
The researchers used climate models together with meteorological data spanning 1960 to 2023 to track how dryland regions have spread over time. By their calculations, arid and semi-arid zones currently cover about 38.6 percent of the planet's land area.
Between 2071 and 2100, that share could rise to between 39.3 and 40.3 percent, depending on how much greenhouse gas is emitted over the coming decades, the study found.
Worst-case scenario
Under the most unfavourable emissions scenario, the total area of drylands would grow by roughly 2.37 million square kilometres, an increase comparable in size to the whole of Algeria.
The most noticeable shifts are expected in Australia and Brazil, along with parts of Africa. The researchers said areas with extremely dry climates are likely to expand fastest of all.
Environmental Research Letters is a peer-reviewed journal that publishes research on climate change, environmental science and sustainability. Drylands, which already include deserts, savannas and semi-arid grasslands, support roughly a third of the world's population and are especially vulnerable to shifts in rainfall and temperature.
Water scarcity and desertification risk
The scientists warned that continued drying could deepen water shortages, accelerate the degradation of ecosystems and speed up desertification in affected regions.
They noted one factor that could partly offset the trend: rising atmospheric carbon dioxide can cause plants to lose less water through their leaves, which slightly reduces the pace of drying. However, the study concluded this effect would not be strong enough to halt the broader global expansion of drylands.
The authors previously reported that drought conditions can also help spread antibiotic resistance, adding to the range of knock-on effects linked to expanding dry regions.
