This post has been corrected.

China is the world’s largest emitter of greenhouse gases, but it is also engaged in a massive tree-planting program that has helped to offset tropical deforestation, and suck some of the climate-changing carbon dioxide out of the atmosphere.

Reforestation efforts in China, combined with regrowth on abandoned farmland in Russia, have helped offset 81% of the loss in above-ground biomass carbon lost to tropical deforestation since 2003, according to a new study in the academic journal Nature Climate Change.

“The increase in vegetation primarily came from a lucky combination of environmental and economic factors and massive tree-planting projects in China,” said lead study author Yi Liu of Australia’s University of New South Wales. Liu said that the carbon storage in Chinese forests increased by about 0.8 billion tons (0.72 billion tonnes) between 2003 and 2012.

Analyzing two decades worth of satellite data, researchers found that the amount of carbon absorbed in vegetation had increased by about 4 billion tons since 2003, even as tropical forests have shrunk in Indonesia and Brazil, and pest infestations and wildfires have cleared forests in Canada and the United States.

"Recent reversal in loss of global terrestrial biomass," Nature Climate Change. Increases in above ground biomass carbon (in blue) can be seen in Russia, China, southern Africa, and northern Australia.

In contrast, southern Africa, northern Australia, and parts of Russia have seen increases in vegetation, helped by more rainfall and higher levels of CO2 in the atmosphere, which helped plants grow “more vigorously,” according to the study. In China, most of the vegetation increase has been in the north, where the country has focused its main reforestation efforts, along with some additional growth in the southeast, Liu said.

Observers say China’s reforestation program in the north—also known as the “Green Great Wall”—is the world’s largest ecological engineering project. The country is building a belt of trees that will stretch some 2,800 miles across north and northwest China in an attempt to stop the advance of the Gobi desert. Overall, the country has planted 13 million hectares (32 million acres) of new forest since 2008, according to the State Forestry Administration.

Critics of China’s plans note that net tree cover continues to fall in the country. That’s due in part to the fact that many of the new trees are non-native fruit and rubber tree plantations that require large amounts of water, and are monocultures prone to disease and pests. According to Global Forest Watch, China has been suffering a loss of about 523,248 hectares (1.29 million acres) of tree cover a year since 2011. Since 2008, that yearly amount appears to be dropping.

(This post originally said that China suffers a “net loss” of about 523,248 hectares. That figure does not take into account tree cover gain.)