China has been setting examples of large-scale environmental restoration, turning barren deserts green, holding back sandstorms, and pulling carbon out of the air. Since 1949, the country has increased its forest cover from around 10% to more than 25%, adding an area of greenery roughly the size of Algeria.Scientists across the world can easily laud these efforts, but it seems nature didn’t. New research shows that all that planting changed how water moves across the country, and it seems not for the good.After 1949, China began increasing its forest cover, but the plants didn’t play well for water distribution in the countryChina’s massive, decades-long tree-planting drive has reshaped the way water moves through the country, and not always for the better, according to a new study published in the journal Earth’s Future.Researchers found that between 2001 and 2020, changes in vegetation cover reduced the freshwater available to people and ecosystems in two major zones, the eastern monsoon region and the northwestern arid region, which together make up about 74% of China’s total land area. Meanwhile, water availability actually increased over the Tibetan Plateau, which covers the rest of the country.Arie Staal, an assistant professor of ecosystem resilience at Utrecht University and a co-author of the study, explained the finding in simple terms, that China’s large-scale regreening, especially the restoration of the Loess Plateau, has effectively “reactivated the water cycle.”
Trees and water get along well; then how and why did this imbalance happen?
The mechanism behind this comes down to evapotranspiration, or the combined effect of evaporation from soil and surfaces and transpiration, where plants release water they’ve drawn up from the ground.Both grasslands and forests usually tend to increase evapotranspiration; the effect is also strongest in forests, since trees can send roots deep enough to tap water even during dry spells.
So, where did all the water actually go?
To track where all this water actually went, the research team, which included scientists from Tianjin University, China Agricultural University, and Utrecht University, combined high-resolution land-cover and rainfall data with an atmospheric moisture-tracking model. They found that evapotranspiration rose faster than precipitation did in comparison, which means that a chunk of water simply escaped into the atmosphere instead of falling back down nearby.Because wind can carry moisture as far as 4,350 miles from where it evaporated, a province that plants forests may end up watering a completely different region, with no local benefit showing up in its own rainfall data.
How has this redistribution impacted China?
This redistribution is important to note because China’s water was already unevenly spread out. The study says that northern China holds around 20% of the country’s water while supporting 46% of its population and 60% of its arable land. The study’s authors wrote that these effects need to be factored into future planning, noting, “understanding these effects is crucial for planning sustainable land and water management in China.“Efforts like the Great Green Wall, Grain for Green, and the Natural Forest Protection Program together account for roughly a quarter of the entire world’s net increase in leaf area since 2000.
