The climate crisis crowd has been pushing countries and companies to plant trees as a means of fighting global warming and reclaiming arid land. However, planting too many trees in places where trees don’t naturally grow has tremendous negative environmental impact. And like most climate policies, such as the use of electric cars that are far worse for the environment than vehicles running on fossil fuel, the tree-planting agenda is shortsighted, using the metric of how many trees were planted as a measure of success rather than calculating any net cost or benefit.
China’s massive regreening campaigns over the past several decades have altered the country’s water cycle in significant and unexpected ways. A new study published in Earth’s Future finds that between 2001 and 2020, large-scale tree planting and grassland restoration increased evapotranspiration across most of China, reducing water availability in both the eastern monsoon zone and the northwestern arid region.
These two regions make up nearly three-quarters of China’s land area. At the same time, precipitation rose in the Tibetan Plateau, which experienced a net increase in available water.
Researchers explain that expanding forests and restoring grasslands reactivate the water cycle by pulling more water from the soil and releasing it into the atmosphere. However, the resulting moisture doesn’t necessarily fall back in the same place. Winds can carry atmospheric water thousands of miles, meaning that water lost through evapotranspiration in one region may become rainfall in a distant area. The study shows that while China’s regreening efforts intensified the overall water cycle, much of the country now loses more water than before.
These findings matter because China already struggles with uneven water distribution. The northern region contains only about 20 percent of the nation’s water but supports nearly half of its population and most of its farmland. Scientists warn that major government water-management projects may fail if they do not account for the water-redistribution effects caused by regreening.
In China’s Three Norths Shelterbelt Program, tree survival rates are often less than 30 percent, biodiversity has decreased, water tables have dropped, and local livelihoods have been disrupted.