Post-1949, China increased its forest cover from 10% to 25%, but scientists found an unexpected side effect: Tree planting shifted water away from East & Northwest towards the Tibetan Plateau

China’s decades-long push to expand its forests has transformed large parts of the country. Since 1949, forest cover has risen from roughly 10% to more than 25%, with vast areas of land brought under vegetation. The effort has helped tackle desertification, reduce erosion and improve the landscape in regions that were once severely degraded. But a new study suggests that there may be another side to this environmental success story: changing the amount of vegetation has also altered how water moves across China.

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How China increased its forest cover after 1949

Large-scale ecological restoration became a major priority in China over several decades, with programmes aimed at restoring degraded land and increasing vegetation. Initiatives such as the Grain for Green programme, the Natural Forest Protection Programme and the Great Green Wall have contributed significantly to the country's greening efforts. Together, such projects have played a major role in the increase in global leaf area recorded since the start of the 21st century. The scale of China's reforestation has therefore been significant, but planting trees in water-stressed regions can also change local water demand.

China’s forests are changing the water cycle

According to research published in Earth's Future, increased vegetation has influenced freshwater availability across different parts of China. The researchers examined changes between 2001 and 2020 and found that vegetation growth was associated with lower freshwater availability in two major regions, the eastern monsoon zone and the northwestern arid zone. Together, these areas account for about 74% of China's land area. In contrast, freshwater availability increased over the Tibetan Plateau.

Why do trees affect water availability?

The answer lies partly in evapotranspiration, the process through which water moves from land and vegetation into the atmosphere. Plants absorb water from the soil and release some of it through their leaves, while water also evaporates from the surrounding land. Forests can have a particularly strong effect because trees often have extensive root systems and can access water from deeper in the soil. As vegetation becomes denser, more water can therefore be transferred from the ground back into the atmosphere.

Where does the water go after trees release it?

The moisture released by vegetation does not necessarily return as rainfall in the same place. Atmospheric winds can transport water vapour over considerable distances before it eventually falls as precipitation. The study used land-cover and rainfall data alongside an atmospheric moisture-tracking model to examine these movements. Researchers found that evapotranspiration increased faster than precipitation in some areas, suggesting that additional water was being transferred into the atmosphere rather than immediately replenishing local freshwater supplies.

Why China’s water redistribution matters

The findings are particularly important because water resources in China are already unevenly distributed. Northern China, for instance, has a relatively small share of the country's water resources despite supporting a large proportion of its population and agricultural land. If vegetation restoration changes where water is stored, consumed or transported through the atmosphere, it could have implications for future water and land-management decisions. The research therefore highlights the need to consider water availability alongside the environmental benefits of large-scale greening.

China’s greening success comes with a new challenge

China's reforestation programmes have delivered major environmental changes, but the research suggests that simply increasing tree cover is not the whole story. Where trees are planted, how much water they require and where atmospheric moisture eventually falls can all influence the wider water cycle. The study isn’t saying that reforestation is a bad thing. Instead, it shows why it’s important to consider local water conditions when planting trees. As China continues its large-scale greening efforts, finding the right balance between increasing vegetation and protecting water resources could help make these projects more sustainable in the long run.


Inputs from TOI