China is the world’s biggest source of human-produced carbon dioxide, responsible for nearly 28 percent of global emissions. Recently, the government announced its intention to reach carbon neutrality by 2060, and to peak those emissions before 2030.

Although the specifics of how the country will reach these goals is not exactly clear, China’s aggressive tree planting policy is likely to play a significant role.

In recent decades, China has planted billions of trees to tackle desertification and soil loss, and to establish vibrant timber and paper industries. Those efforts have led China to become the country with the fastest rate of greening, helping to increase the global green leaf area. Greening, as the term indicates, refers to the process of making somewhere greener by planting grass, trees, and plants there.

Obviously it’s good that China is experiencing so much greening, but what international scientists are only just realizing is how much carbon dioxide absorption these new forests are responsible for. In a new analysis published in Nature Journal, the scientists identified two areas in the country where the scale of carbon dioxide absorption by new forests has been underestimated. Taken together, these areas account for a little over 35 percent of China’s entire land carbon “sink,” the group says.

The two previously under-noticed carbon sink areas are located in China’s southwest, in the Yunnan, Guizhou and Guangxi provinces as well as its northeast, in the Heilongjiang and Jilin provinces. The land biosphere over southwest China is by far the largest single region of uptake with a sink of about -0.35 petagrams per year, representing 31.5 percent of the Chinese land carbon sink. A petagram is a billion tonnes.

According to researchers, the land biosphere over northeast China is seasonal, so it takes up carbon during the growing season, but emits carbon otherwise. This evens out to a net annual uptake of -0.05 petagrams per year, representing about 4.5 percent of the Chinese land carbon sink. To reach this conclusion, the researchers relied on a “range of ground-based and satellite data-driven evidence.”

Although the results of the study display the great carbon-absorbing ability of forests, we shouldn’t get too excited as China has a long way to go to slash the massive amount of emissions it produces each year.

“With China setting out its ambition for net zero, it’s obviously crucial to know the size of the national carbon sink, so this is an important study,” said Richard Blank, director of the Energy and Climate Intelligence Unit (ECIU), a non-profit think-tank working on climate change and energy issues. “However, although the forest sink is bigger than thought, no-one should mistake this as constituting a ‘free pass’ way to reach net zero.”