At the edge of China's Taklamakan Desert, rows of trees are slowly edging into one of the world’s harshest landscapes after decades of planting. Scientists say this shows how human action can transform extreme environments – but warn of the cost to water resources, and that such schemes might not be easy to repeat elsewhere.
The Taklamakan, in the vast Xinjiang region, is one of the driest deserts on Earth. Surrounded by mountains that block humid air, it has long been hostile to plant life.
China launched its Great Green Wall project in 1978 to slow the spread of deserts in the north of the country. The programme, which stretches across roughly 4 million square kilometres, is due to run until around 2050.
Authorities said in 2024 they had completed a green belt around the desert, planting 66 billion trees along roughly 3,000 kilometres.
A study published in January in the Proceedings of the National Academy of Sciences found this is already having an impact, with the region becoming greener, rainfall increasing and carbon absorption improving.
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Chain reaction
Using satellite images and field data, researchers described a clear pattern: more trees brought more rain, more rain fed more vegetation and more vegetation pulled more carbon dioxide from the air.
During the wet season from July to September, rainfall rose by up to 16.3 millimetres per month. While that would be a low rainfall in most places, in a desert such as the Taklamakan it's a notable increase.
China’s forest cover has grown from 10 to 25 percent of its territory over recent decades. During the wet season, carbon dioxide levels in the regional atmosphere fall by around three parts per million compared with the dry season.
“We observed three very clear trends,” explained Yang Jiani of NASA’s Jet Propulsion Laboratory, which uses satellite data to study the Earth’s climate.
"First, vegetation cover has increased significantly over the past 20 years. Second, the intensity of photosynthesis has continued to grow. And third, the ecosystem’s ability to absorb carbon dioxide is also increasing.”
Each hectare in the planted zones absorbs around 1.7 tonnes of carbon dioxide per year, Yang told RFI. Across the entire desert, that would add up to 58 million tonnes annually.
The findings show that human action can strengthen carbon storage even in extreme dry landscapes, co-author Yuk Yung told the news website Live Science.
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Water pressure
While the results suggest the project is having a real impact on the desert environment, they do not answer a key question – what it means for water resources in such a dry region.
That concern has been raised by critics for several years. Mass tree planting could come at the expense of water resources for future generations, Jiang Gaoming of the Chinese Academy of Sciences warned. Grasses, which need less water, would be more effective in fighting desertification, he argued.
Other researchers have raised broader concerns about how such projects reshape fragile ecosystems. Planting trees in very dry regions could have unintended effects, French hydrologist Emma Haziza told RFI.
“Once you start modifying an extremely arid environment and planting on a massive scale, a huge number of factors will determine whether it is a good or a bad idea,” she said.
Planting trees in very dry regions can shift water out of the ground and into the air, Haziza explained, adding that moisture can later fall as rain somewhere else – sometimes far away – but the area where the trees are planted may lose water.
“We are dealing with a complex system that requires many variables to be taken into account,” she said.
A separate study published in October in the journal Earth’s Future, by Chinese and European researchers, found that changes in land cover between 2001 and 2020 shifted rainfall towards the Tibetan Plateau, while reducing it in eastern China and especially in the north-west.
The study did not directly assess groundwater or quantify the specific impacts on the regional water cycle. “This article does not allow us to confirm that there is a risk of overexploiting future water resources,” Yang said.
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Long-term viability
The long-term stability of the desert’s carbon storage also remains uncertain.
“A green belt this vast, stretching thousands of kilometres, will certainly change the carbon sink, but for how long?” Haziza asked.
Carbon storage depends on the water cycle and soil moisture, she explained. “As long as the soil is fully moist, it can act as a carbon sink. Once it dries out, that function disappears.”
Other researchers say the picture is more complex. Changes to air circulation and the water cycle could produce unexpected results, Li Zhaoxin, a senior researcher at France’s national scientific research centre CNRS, told RFI.
The field is still new and sometimes produces inconsistent or even contradictory findings, with outcomes often depending on local conditions. This desert greening effort also has clear limits.
“The case of the Taklamakan Desert is relatively rare on a global scale,” Yang said, because it reflects decades of continuous investment by a single country and relies on locally adapted species backed by scientific monitoring.
The project also integrates engineering with ecology and is not a model that can be easily reproduced, she said. Rather than a universal solution, it is a demonstration that it can be done, and each country must adapt to its own specific situation.
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An African echo
The Chinese model has travelled beyond the country’s borders, though not without challenges. Africa’s Great Green Wall, launched by the African Union in 2005, aims to stretch from Dakar to Djibouti, over 7,800 kilometres in a corridor 15 kilometres wide.
The project has had mixed results and has been slowed by political and financial difficulties.
Despite this, China continues to promote its experience in the Taklamakan as an example for African countries.
For Yang, the lesson is that such projects can work, but only under certain conditions.
“Our research mainly shows that with scientific management and long-term investment, even the most remote and arid desert areas can become functioning carbon sinks,” she said. “But a balance will have to be found between carbon gains and water security.”
This article was adapted from an article in French, using original reporting by Yang Mei for RFI's Chinese-language service.
