China’s vast tree-planting campaigns have not only greened deserts and hillsides, they have also altered how water moves through the country’s air, soil and rivers. By turning bare land into forest at extraordinary speed, the government has effectively reengineered the national water balance, with benefits for erosion and dust control but growing risks for rivers, wetlands and farms.
As the climate warms and rainfall patterns shift, the scale of this transformation is forcing a hard question: how much new forest can China sustain before the hydrological costs outweigh the ecological gains? I see a country now grappling with the second chapter of its greening story, where the challenge is no longer how many trees to plant, but where, what kind and at what water price.
China’s tree-planting revolution, in numbers
China has spent decades turning itself into one of the world’s most aggressively afforested nations, treating trees as a strategic tool against dust storms, soil erosion and climate change. The country’s leadership has framed this as a national mission, and the result is a landscape where forests now cover vast swaths of territory that were once cropland, grassland or degraded scrub, a shift that has inevitably reshaped how water is stored and released across the land.
According to China’s ninth National Forest Inventory, known as the National Forest Inventory (NFI), total forest area in China expanded significantly during 2000–2018, with the NFI documenting large gains in both planted and natural forests. Those figures, which cover the period 2014–2018 in detail, show how systematically the state has pushed tree cover across multiple regions, from the humid south to the arid north, and they underpin the scale of the hydrological changes now emerging.
How mass planting rewired China’s water cycle
Planting trees at continental scale does more than change the view from space, it changes how water moves from soil to sky and back again. Forests intercept rainfall, pull moisture from the ground through their roots and release it as vapor, a process that can cool local climates and influence where clouds form and rain falls, sometimes hundreds of kilometers away.
Researchers examining China’s greening have found that this process has effectively transformed the country’s hydrology, with large-scale planting altering evaporation, runoff and even regional precipitation patterns. One analysis describes how China’s Massive Tree Planting Has Transformed Its Water Cycle in Unexpected Ways, highlighting that the new forests are now a major driver of water redistribution that scientists are still trying to fully understand.
From dust storms to depleted rivers
The original motivation for many of these projects was straightforward: stop deserts from marching east and choking cities with dust. Programs such as the Great Green Wall in northern China were designed to stabilize soils and cut the frequency of sandstorms that once regularly blanketed Beijing and other urban centers, and by many accounts they have succeeded in reducing dust and improving local air quality.
Yet the same trees that anchor dunes and hillsides also consume large amounts of water, and in arid and semi-arid regions that has come at a cost to rivers, lakes and groundwater. Hydrological studies show that ecological restoration in the North China Region, including extensive afforestation, has exacerbated an agriculture-induced water crisis by increasing plant water use and reducing total water storage, or TWS, even as climate conditions in the coming decades could favor some recovery if planting intensity is curbed.
Warnings from scientists about water stress
As the tree-planting drive accelerated, scientists began to warn that the strategy could collide with basic hydrological limits, especially in a warming world. In northern and western regions where rainfall is scarce, adding dense forests on top of existing water demands risks pushing ecosystems and communities into chronic shortage.
Researchers have cautioned that Researchers warn that the country’s push to hold back its deserts could strain water resources, noting that China has planted billions of trees in regions where precipitation is low and that some of these species require more water than local conditions can reliably supply. Those warnings have sharpened as climate models project hotter, drier conditions in some of the very areas where planting has been most aggressive.
Evidence from long-term hydrological studies
To move beyond theory, scientists have turned to decades of data on rainfall, runoff and groundwater to see how afforestation has changed water availability on the ground. By comparing conditions before and after large-scale planting, they have been able to tease out the specific impact of artificial forests on regional water supply.
One detailed study of artificial afforestation conducted a spatiotemporal analysis of abrupt changes in water supply between 1980 and 2015, finding that large-scale planting significantly altered the balance between precipitation, evaporation and runoff. The authors concluded that ecological restoration projects, while beneficial for soil and vegetation, had in some basins reduced water supply, a pattern captured in their assessment of Ecological Risks Arising from the Impact of Large-scale afforestation on regional hydrology.
When forests compete with wetlands and farms
As forests expand, they inevitably overlap with other ecosystems and land uses that also depend on limited water, particularly wetlands and irrigated agriculture. In some regions, the push to plant trees has come at the expense of wetlands that store floodwater, support biodiversity and recharge aquifers, creating a trade-off between two forms of ecological value.
Analyses of land-use change in China have documented a clear trade-off between tree planting and wetland conservation, with the expansion of forest area during 2000–2018 in some cases coinciding with wetland loss. That same period also saw pressure on cropland water supplies, as new plantations and existing farms drew from the same rivers and aquifers, forcing local authorities to juggle competing demands for irrigation, ecological flows and urban consumption.
National-scale shifts in water distribution
When a country the size of China changes its land cover so dramatically, the effects are not confined to individual river basins. The cumulative impact of billions of trees has begun to reshape how water is distributed across the entire territory, influencing which regions see more evaporation, which retain more soil moisture and how much runoff ultimately reaches major rivers.
Reporting on these trends notes that China has planted so many trees that it has changed the entire country’s water distribution, with efforts to slow land degradation and desertification now recognized as a driver of large-scale hydrological change. One account describes how China’s efforts to slow land degradation have altered where water is stored and how it moves, a reminder that even well-intentioned ecological projects can have far-reaching side effects.
Teleconnections: when greening one region dries another
Forests do not just affect the water cycle locally, they can also influence weather patterns far away through atmospheric teleconnections. By changing how much moisture is released into the air and how heat is exchanged between land and atmosphere, large regreening projects can shift storm tracks and rainfall in distant regions, sometimes in ways that are hard to predict.
Analyses of China’s programs have highlighted that other large regreening projects in one region can affect precipitation in another, underscoring the complexity of continental-scale land management. One report on how China has planted so many trees it changed its water balance notes that Other large regreening projects often affect precipitation in another, a finding that suggests China’s choices are now part of a broader planetary conversation about how land use and climate interact.
Adapting the strategy in a warming climate
Faced with mounting evidence that not all trees are equal in water terms, Chinese planners and scientists are increasingly focused on what kinds of forests make sense in which regions. The emerging consensus is that in arid and semi-arid zones, planting should favor drought-tolerant species, lower densities and mixed vegetation that uses less water while still stabilizing soils and storing carbon.
Hydrological modeling indicates that climate conditions in the coming decades could favor some recovery of total water storage if afforestation intensity is moderated and better aligned with local hydrometeorological conditions and plant water use. One assessment of ecological restoration in the North China Region concludes that climate alone would allow climate conditions in the coming decades to support TWS recovery, but only if afforestation intensity is no longer enhanced and if restoration is tailored to local water realities.
What China’s experiment means for the world
China’s experience is now a live case study for other countries that see tree planting as a simple climate solution. The lesson is not that forests are a mistake, but that large-scale planting without hydrological planning can shift water scarcity from one place to another, or from one sector to another, in ways that may only become visible years later.
As governments and companies promote global campaigns to plant billions of trees, China’s record shows why any such effort must start with a clear-eyed understanding of water. The country’s own profile, captured in global references to China as a vast, diverse and heavily populated state, makes its hydrological experiment uniquely consequential, and its evolving strategy will help determine how the world balances forests, food and freshwater in a hotter century.
More from MorningOverview