China’s decades‑long campaign to restore forests and grasslands has altered the country’s water distribution in ways scientists are only beginning to grasp. Now, new research shows that large‑scale “regreening” projects have reactivated the water cycle, shifting rainfall and evaporation patterns across vast regions.
Between 2001 and 2020, vegetation changes reduced water availability in the eastern monsoon belt and the arid northwest — areas that together cover nearly three‑quarters of China’s landmass. At the same time, water supplies increased across the Tibetan Plateau, according to findings published in Earth’s Future on October 4.
“We find that land cover changes redistribute water,” said study co‑author Arie Staal, assistant professor of ecosystem resilience at Utrecht University. “China has done massive‑scale regreening over the past decades. They have actively restored thriving ecosystems, specifically in the Loess Plateau. This has also reactivated the water cycle.”
Staal explained that forests and grasslands intensify evapotranspiration — the combined processes of evaporation and plant transpiration — which, in turn, influences rainfall. “Both grassland and forests generally tend to increase evapotranspiration,” he said. “This is especially strong in forests, as trees can have deep roots that access water in dry moments.”
China’s most ambitious project, the Great Green Wall, began in 1978 to halt the expansion of the desert in the north. Over five decades, forest cover has grown from about 10% of the country’s land in 1949 to more than 25% today — an area roughly the size of Algeria. Officials announced last year that vegetation now surrounds the nation’s largest desert, though planting will continue to keep desertification at bay.
Other initiatives launched in 1999 include the Grain for Green Program, which pays farmers to convert cropland into forest and grassland, and the Natural Forest Protection Program, which bans logging in primary forests while promoting afforestation. Together, these efforts account for a quarter of the global net increase in leaf area between 2000 and 2017.
The study found that evapotranspiration rose more than precipitation overall, meaning some water was lost to the atmosphere. Winds can carry that moisture thousands of kilometres, so rainfall often occurs far from where the water evaporated. “Even though the water cycle is more active, at local scales, more water is lost than before,” Staal said.
This redistribution has profound implications for water management. Northern China holds only 20% of the country’s water but supports nearly half the population and most of its farmland. The researchers warn that government measures may fall short if they fail to account for regreening’s impacts.
Staal added that similar restoration projects worldwide could be influencing water cycles elsewhere. “From a water resources point of view, we need to see on a case‑by‑case basis whether certain land cover changes are beneficial or not,” he said. “It depends, among other things, on how much and where the water that goes into the atmosphere comes down again as precipitation.”
