In 1981, China began planting billions of trees to restore degraded land. Decades later, the 78-billion-tree effort produced a surprising outcome: it altered the water cycle, sending more rain to some regions while drying out others

China has pursued environmental restoration on a scale few other countries have attempted. One of the most recognizable examples is the Three-North Shelterbelt, better known as “The Great Green Wall,” a vast planting program designed to address desertification, protect land from erosion and reduce the impact of desert storms.

The program officially dates back to 1978, although the headline refers to the enormous expansion of tree planting that followed in the early 1980s. By 2024, China's state-sponsored media reported that the Great Green Wall had reached completion.

The scale is difficult to imagine. As per the Reuters, China had established around 116,000 square miles of new trees, while national forest coverage rose from about 10 percent in 1949 to roughly 25 percent in 2024.


The tree-planting campaign has disclosed something that cannot be measured simply by counting trees. A 2025 study in Earth’s Future discovered that China's dramatic increase in vegetation has also impacted the country's distribution of water.

The hidden consequence of making China greener

Researchers from Tianjin University, China Agricultural University in Beijing and Utrecht University in the Netherlands investigated changes between 2001 and 2020. Their work indicates that expanded vegetation was connected with lower water resources in two significant areas: China's eastern monsoon area and its northwestern arid region.

Those findings are especially notable because the impacted places cover roughly 74 percent of China's land area, as per Live Science.

Along with the Great Green Wall, the Grain for Green Program and the Natural Forest Protection Program contributed to the country's changing vegetation patterns; both of those programs started in 1999.

As vegetation cover changes, the movement of water between soil, plants and atmosphere can change as well. The result is a hydrological system in which water that might once have remained available in one region can be transferred elsewhere.

“These shifts caused changes in precipitation, directing more moisture to the Tibetan Plateau, which saw an increase in water availability,” the authors wrote. “In contrast, eastern and northwestern China experienced a decrease in water availability, with the northwest losing the most due to substantial moisture moving to the Tibetan Plateau.”

A forest can change the water balance

One of the study's major findings is that different land-cover changes do not have identical consequences.

Researchers analyzed rapid land-use/cover changes, regarded as LUCC, and compared transitions such as grasslands becoming forests and croplands becoming grasslands. These changes influenced evapotranspiration, precipitation and water availability at various rates.

A shift from grassland to forest, for example, increased evapotranspiration and precipitation but nevertheless had a negative impact on water availability. This illustrates why rainfall totals alone cannot state the complete narrative.

More vegetation can mean more water is transferred into the atmosphere. More precipitation in an area also does not necessarily mean that the same place ends up with more usable water. Atmospheric circulation can move moisture in geographical boundaries.

The distinction matters when assessing significant restoration schemes. A project can get its intended goal of increasing vegetation while simultaneously changing other parts of the regional water system.

The broader lesson from China's experiment

China's experience provides an unusual example of how an environmental intervention can produce challenges that become visible only after decades.

The goal was straightforward: increase vegetation, protect vulnerable land and slow desertification. But the enormous scale of the transformation means the effects extend beyond the places where trees were planted.

The study indicates that future reforestation policies should analyze not just forest coverage but also regional precipitation, evapotranspiration and water availability.

The authors put that wider concern directly:

“Our findings highlight that land cover changes can redistribute water resources between regions,” the authors wrote. “Understanding these effects is crucial for planning sustainable land and water management in China.”

The findings do not overturn the value of restoring degraded ecosystems. Instead, they illustrate that environmental restoration needs to be planned as part of a connected system. A tree planted in one region can impact the movement of water far beyond its roots, making the long-term management of forests inseparable from the management of water.

Source: POPULAR MECHANICS

FAQs:

Q1. Why did China plant so many trees?


China launched large-scale reforestation programs to combat desertification, reduce soil erosion and protect vulnerable landscapes. The Three-North Shelterbelt became one of the country's largest environmental restoration projects

Q2. What is the Great Green Wall?

The Great Green Wall is another name for China's Three-North Shelterbelt. It was created to expand vegetation across northern areas and help limit desertification and erosion.