Successes in the fight against desertification – a spoonful of tar in a barrel of honey

According to those interested in environmental protection in the water context, one obvious threat is desertification. Recently, however, there have been optimistic reports on this topic. Analysis of images taken by Landsat between 1984 and 2024 showed that the area of deserts worldwide has decreased. The average annual decrease is nearly 23,000. ^km2.

Is desertification retreating? Not always and not everywhere

Detailed data show that this is not a uniform trend. At the beginning of the observation, the global area of deserts was increasing. The same was true in the 2005-2009 period. However, the decline between 1995-2005 and after 2009 has prevailed. Geographically, too, the situation is far from consistent. China is mainly responsible for the global containment or even reversal of desertification . There are similar trends in Central Asia, southern Africa and Australia, but they are weaker. In contrast, deserts in the Americas, northern Africa and the Middle East continue to expand their reach.

China (and not only China) is known for highlighting its achievements and downplaying problems. This time, however, it seems that reality is matching the propaganda of success. This is confirmed by the ideal satellite data for assessing land cover. An article on the results of the reforestation of the Takla Makan desert, published at a similar time by a Chinese-American team of researchers, is also cause for optimism. The outskirts of this desert are covered by the Green Great Wall project, which was initiated almost half a century ago. Just as the Great Wall of China was once intended to protect the country’s civilization from barbarian attacks, today the forest planting belts are intended to stop the Gobi desert’s onslaught on agricultural land.

This project has not always been successful, but in the case of Takla Makan it is proving to be successful. It is one of the driest regions in the world, at which even the neighboring Gobi does not seem so scary. However, the Takla Makan desert is confined to a basin, which keeps it from expanding, unlike its larger neighbor. The project has managed to tree its periphery, and the induced change in the local water cycle means that rainfall totals increase, allowing vegetation to grow more luxuriantly. Scientists also hope to increase the absorption of carbon dioxide from the atmosphere.

No free lunch, or water balance on the downside

Other publications, however, dampen the enthusiasm somewhat. One of them, prepared mainly by researchers from the Chinese Academy of Sciences, points out that not all measures are equally effective. China is a large country, and while its success in halting desertification is notable globally, many agricultural areas are still degraded. The intensification of agriculture in areas uprooted from the steppe is leading to water shortages. We wrote more about this in the January issue of Water Matters.

Another study provides an even worse perspective. It does not question the success in stopping the desertification of steppes and the stepping of forests, but it does point out the cost of these measures. And not just economically, but especially environmentally (which will also hit the economy as a consequence). The Takla Makan desert example seems ideal, but it is out of context. At the scale of China as a whole, land-cover changes modify the water cycle in such a way that its balance comes out in the negative.

In the water cycle, evaporation is a key factor. In dry regions it is low, but trees, thanks to their root systems, reach deeper layers from where they suck up water and can grow. Terrestrial plants, in order to live, must act as pumps that move water from the root zone through the wood bundles to the stomata in the leaves. Large trees are much more efficient in this regard than other representatives of the flora. In addition, during periods of drought, herbaceous plants wither, which stops the transpiration process.

In trees, these mechanisms are inhibited, such as by leaf shedding, but do not cease completely, which is why forests deplete groundwater more strongly than steppes, let alone deserts. This water then evaporates from the leaves, which increases the humidity of the air. If it returns in the form of rainfall, as is the case in the Takla Makan region, it can be used by herbaceous plants and crops. However, it turns out that westerly winds prevail throughout China, blowing the moist air out to sea.

In certain areas of Tibet, where vegetation is poor (steppe or desert; more due to low temperatures than low rainfall), the amount of available water increases. Similarly, in some points in eastern China. However, over most of the country, the amount of available water as a result of land-cover changes (not only the reforestation of the Great Green Wall, but also deforestation in traditionally forested areas or urbanization) is decreasing. This includes the western vicinity of the Takla Makan desert itself and some regions around the Gobi desert, but also the Sichuan bamboo forests, home to pandas. Although total precipitation has increased in many places, the sum of evaporation from the earth’s surface (evaporation) and from plants (transpiration) has increased even more.

When making statements about the water crisis, one usually hears retorts from those who downplay it, saying that the amount of water in nature is constant. Their aim is to undermine the fact that there is a crisis and to argue that there is no basis for restricting economic activities that affect water relations. Indeed, the amount of water on Earth is not changing, but its location is changing. Thanks to afforestation actions in China’s deserts, some of the water that was previously in the ground has been released into the atmosphere and is finding its way downwind to the Pacific Ocean. For Chinese agriculture and industry, this could have dire consequences.

In writing this article, I used the following publications:

Huijuan Wu, Huayu Lu, Mengchun Cui, Marzieh Mokarram, Pengfeng Xiao (2026) Global Desert Variations During 1985-2024 Associated With Effective Water Availability Geophysical Research Letters https://doi.org/10.1029/2025GL120826

Salma Noor , Xun Jiang , Xinyue Wang, Jiani Yang, Sally Newman, King-Fai Li, Liming Li, Le Yu, Xiyu Li, Yuk L. Yung (2026) Human-induced biospheric carbon sink: Impact from the Taklamakan Afforestation Project Proceedings of the National Academy of Sciences 123(4):e2523388123 doi 10.1073/pnas.2523388123

Qiang An, Liu Liu, Arie Staal, Kun Yang, Yongming Cheng, Jing Liu, Guanhua Huang (2025) Land Cover Changes Redistribute China’s Water Resources Through Atmospheric Moisture Recycling Earth’s Future https://doi.org/10.1029/2024EF005565