Billions of trees and grasses planted by China to fight climate change caused water to evaporate faster than rain could replenish it.
China has raised its forest cover from about 10% of the country in 1949 to more than 25% today, an added area roughly the size of Algeria.
New research finds that all those trees have moved the country’s water around, and not in the direction anyone planned.
Trees move water around
Between 2001 and 2020, changes in vegetation cover reduced the fresh water available to people and ecosystems across the eastern monsoon region and the northwestern arid region.
Those two zones together account for 74% of China’s land area, according to a study published in the journal Earth’s Future.
Over the same period, water availability rose in the Tibetan Plateau region, which makes up the rest of the country.
Arie Staal, an assistant professor of ecosystem resilience at Utrecht University in the Netherlands, is a co-author of the study, and he described the core finding as a redistribution of water driven by land cover change.
He noted that China’s decades of large-scale regreening, particularly the restoration of ecosystems on the Loess Plateau, have reactivated the water cycle itself.
How the cycle sped up
Three processes shift water between the continents and the atmosphere, with evaporation and transpiration carrying it upward and precipitation bringing it back down.
Evaporation pulls water from surfaces and soils, while transpiration releases water that plants have drawn out of the ground, and together the two are called evapotranspiration.
That combined figure rises and falls with plant cover, with how much water is available, and with the amount of solar energy reaching the land, Staal said.
Both grassland and forest tend to push evapotranspiration up, and the effect is strongest in forests, because trees can send roots deep enough to reach water during dry spells.
Where the water went
To trace these effects, the researchers combined high-resolution data on evapotranspiration, precipitation, and land-use change with an atmospheric moisture tracking model.
Evapotranspiration rose more than precipitation did overall, which means a share of the water simply left for the atmosphere and did not come back down nearby.
Forest expansion in the eastern monsoon region and grassland restoration across the rest of the country both increased evapotranspiration, but precipitation increased only over the Tibetan Plateau.
Everywhere else, water availability fell. “More water is lost than before,” Staal said of conditions at local scales, even as the cycle as a whole runs faster.
Wind carries it far away
The pattern is not uniform across China, and the reason is that moisture does not stay where it rises.
Winds can carry water as far as 4,350 miles (7,000 kilometers) from its source, so evapotranspiration in one place regularly determines rainfall somewhere else entirely.
A province that plants forests may therefore be watering a region well beyond its own borders, without any of that showing up in local rainfall records.
The north was already dry
This matters for water management because China’s water was unevenly distributed to begin with.
The north holds about 20% of the country’s water while housing 46% of the population and 60% of the arable land, according to the study.
The government is working to address that imbalance, but the authors argue those measures will probably fail if the redistribution caused by regreening is left out of the calculation.
Decades of planting
The largest of these efforts is the Great Green Wall across the arid and semi-arid north, launched in 1978 to slow the spread of deserts.
In November 2024, workers planted the final stretch of a 3,046-kilometer belt encircling the Taklamakan, completing the ring around China’s largest desert after more than four decades of work.
Two further programs began in 1999. Grain for Green pays farmers to convert cropland into forest and grassland, while the Natural Forest Protection Program bans logging in primary forests and promotes planting.
Together, China’s restoration initiatives account for 25% of the global net increase in leaf area between 2000 and 2017.
What the trees also did
Other findings have been more encouraging. A study published in January 2026 reported that the vegetated rim of the Taklamakan now absorbs more carbon dioxide than the desert releases, making it a net carbon sink.
That outcome was never the point of the project, which was built to protect roads, farms, and settlements from advancing dunes.
Critics have also noted that survival rates for planted trees are often low, and that sandstorms still reach Beijing each spring.
Not an argument against trees
None of this says that planting was a mistake, and the study does not make that claim.
The programs were built to hold back deserts and to keep soil in place, and on those terms they have delivered.
What it says is that land cover change has hydrological consequences that have to be assessed one case at a time, since whether a change helps depends on how much water reaches the atmosphere and where it falls again.
Restoration and afforestation elsewhere are likely shifting water cycles in the same way, in countries that have not yet measured it.
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