China is planting trees to stop deserts expanding.Credit: Wang He/Getty

China has planted billions of trees over the past four decades as part of its fight against expanding deserts, mostly in its north. Each year, the country sows seedlings over an area nearly the size of Ireland. It is even sharing its desert-control methods with others as part of its massive Belt and Road trade initiative.

The trees have held back China′s deserts. But some scientists worry that the planting could worsen water scarcity. Many of the trees are not native to the regions where they have been planted, and they use a lot of water — despite being placed in areas that are experiencing less rainfall due to global warming.

“The idea is nice, but it’s kind of foolish to plant trees in a desert,” says Troy Sternberg, a geographer at the University of Oxford, UK.

Chinese scientists say there are good reasons to plant vegetation in barren areas but that the programme needs to take into account local conditions. They say local and national governments are already planting more shrubs, herbs and other forms of native vegetation that need less water.

Greening China

The Gobi Desert and similarly arid regions in China are expanding as processes such as overgrazing deplete vegetation on their borders, allowing wind and gravity to erode soil. China’s largest tree-planting drive, the Three-North Shelter Forest Program, also called the Great Green Wall, is designed to halt that encroachment. The government says that it has planted more than 66 billion trees across 13 provinces in the country’s north since the programme began in 1978.

Around the year 2000, deserts across the country were expanding by 10,400 square kilometres a year, says the government. But in 2017, the State Forestry Administration reported that China’s deserts were shrinking by more than 2,400 square kilometres a year.

A 2018 study1 analysing satellite data from the US National Oceanic and Atmospheric Administration found there has been an increase in forest cover consistent with government statistics, but suggested that changes in logging policy were more important factors than afforestation — planting forests where none had grown before.

In 1999, the Chinese government began planting millions of trees in its Grain for Green Program, intended to repair damaged farmland in key agricultural in the northern Loess Plateau, which is roughly the size of France. “I was there two years ago, and it is indeed amazing that once bare landscapes are now almost fully covered by plants,” says Philippe Ciais, a climate researcher at the Laboratory of Climate and Environmental Sciences in Gif-sur-Yvette near Paris.

And the afforestation drive is continuing apace: in 2018, the State Forestry Administration announced a target of 30% forest coverage by 2050. At the moment, the coverage is around 22%.

The growth of forests is significant and necessary progress in the fight against desertification, says Jianping Huang, a climate researcher at Lanzhou University.

But it’s still too early to determine whether it has solved the problem, says Congbin Fu, director of the Institute for Climate and Global Change Research at Nanjing University. Land restoration is usually a long-term process — it can take several decades or even 100 years, he says.

Shrubs and herbs are often more suitable than trees for the desert environment.Credit: Wang He/Getty

Water shortages

There are some pitfalls to mass tree planting. In southwestern China, researchers have found that farmers were cutting down native vegetation so they could collect money for sowing non-native plants in government programmes4.

Then there are water shortages. Large parts of China — including some areas where trees are being planted — are becoming drier. A study2 published online in July found that semi-arid areas in the country grew by 33% between 1994 and 2008 compared to between 1948 and 1962. Another paper3, co-authored by Sternberg, found that arid areas in China had increased by roughly 1.6 million square kilometres, about the size of Iran, since 1980 — probably due in large part to anthropogenic climate change.

Many of the plant species introduced to the Loess Plateau use more water than native vegetation. A 2016 study5 co-authored by Ciais found that the revitalized ecosystem is already sucking up rainfall and reducing the amount of water that runs off to rivers; a drier climate could exacerbate the situation and trigger water shortages for humans. A modelling study6 co-authored by Fu and published last month reached similar conclusions, and cautioned against continuing the Grain for Green Program.

Alternative approach

Considering water shortages is important, says Shixiong Cao, an ecologist at Beijing Forestry University. He thinks the national forestry department has recognized the error of planting trees in arid areas, and that in recent years, the department and local governments have moved towards planting shrubs with lower water requirements.

The head of the forestry department, Zhang Jianlong, told Chinese state media in March that efforts should go towards keeping vegetation healthy, rather than simply planting trees. “Also, species should be planted with the right techniques in inhospitable places.”

Cao says planting programmes work best when local governments engage with researchers and communities to find ways to seed less-thirsty plants that create economic value. These include herbs used in traditional Chinese medicine, some of which can grow symbiotically with shrubs, and which farmers can harvest and sell.