China’s forests that absorb more pollutants than previously thought | ...

An international team identified two Chinese areas where the scale of carbon dioxide absorption by new forests has been underestimated.

Together, these areas account for just over 35% of China’s total carbon capture, the group says.

The researchers’ analysis, based on terrestrial and satellite observations, was published in the scientific journal Nature.

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Carbon sequestration occurs when a reservoir – such as forests – absorbs more carbon than it releases, thus reducing the concentration of CO2 in the atmosphere.

China is the world’s largest emitter of man-made carbon dioxide, responsible for about 28% of global emissions.

But recently, the country declared its intention to peak these emissions before 2030 and then move on to carbon neutrality by 2060.

The specifications of how the country would achieve these goals are unclear, but they must inevitably include not only dramatic reductions in the use of fossil fuels, but also ways of removing carbon from the atmosphere.

“Achieve China’s zero carbon target by 2060, recently announced by Chinese President Xi Jinping, will involve a major shift in energy production and also the growth of sustainable carbon sequestration reservoirs, “says study co-author Yi Liu of the Chinese Academy of Atmospheric Physics (IAP). of Science in Beijing.

“The afforestation activities described in the article [da Nature] will play an important role in achieving that goal, “he adds to BBC News.

The increase in forests in China has been evident for some time. Billions of trees have been planted in the past few decades to combat desertification and soil loss and to establish vibrant wood and paper industries, but until now it has been estimated that their effect has been minor.

The new study refines estimates of how much CO2 all of these extra trees can absorb as they grow.

The latest analysis examined a number of data sources. They comprised forestry records, satellite remote monitoring measurements of green vegetation, soil water availability; and CO2 observations, again made from space, but also by direct sampling of air at ground level.

“China is one of the largest global emitters of CO2, but how much is absorbed by its forests is very uncertain,” says IAP scientist Jing Wang, the report’s lead author.

“Working with CO2 data collected by the Chinese Meteorological Administration, we were able to locate and quantify how much CO2 is absorbed by Chinese forests.”

The two underestimated carbon sequestration areas are concentrated in southwest China, in Yunnan, Guizhou and Guangxi provinces; and its northeast, particularly in Heilongjiang and Jilin provinces.

The terrestrial biosphere over southwest China, by far the largest individual absorption region, represents a sequestration of about -0.35 petagramas per year, representing 31.5% of the Chinese terrestrial carbon sequestration.

One petagram is equivalent to 1 billion tons.

The terrestrial biosphere over northeast China, the researchers say, is seasonal, so it absorbs carbon during the growing season, but emits carbon on other occasions. Its annual net balance is approximately – 0.05 petagramas per year, representing approximately 4.5% of China’s carbon sequestration.

To put these numbers into context, China was emitting 2.67 carbon petagrams as a result of using fossil fuel in 2017.

Co-author Paul Palmer, a professor at the University of Edinburgh in the United Kingdom, said the size of forest reservoirs may seem surprising, but pointed to the very good agreement between space and ground measurements as a reason to trust the analysis.

“Bold scientific statements must be supported by large amounts of evidence and this is what we did in this study,” the NERC National Earth Observation Center scientist tells BBC News.

“We have assembled a series of evidence based on terrestrial and satellite data to form a consistent and robust narrative about the Chinese carbon cycle.”

Professor Shaun Quegan, from the University of Sheffield, UK, studies the Earth’s carbon balance, but was not involved in this research.

He says the discovery in the northeast of China was not a surprise to him, but that of the southwest area. Warns, however, that the new forests’ ability to attract carbon decreases over time, as their growth rate slows and the systems adopt a more stable state.

“This (scientific) article clearly illustrates how various sources of evidence for spatial data can increase our confidence in carbon flow estimates based on sparse soil data,” he says.

“This bodes well for the use of the new generation of space sensors to help nations’ efforts to fulfill their commitments under the Paris Agreement.”

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Quegan is the principal scientist on the next European mission, Biomass, a radar ship that will “weigh” forests. It will be able to tell you exactly where the carbon is being stored, whether in tree trunks, on the ground or elsewhere.

Another noteworthy future satellite project in this context is the EU Sentinel mission (currently codenamed CO2M), to measure CO2 in the atmosphere at very high resolution.

Richard Black is director of the Energy and Climate Intelligence Unit (ECIU), a nonprofit organization that works on climate change and energy issues.

He says: “With China setting its zero-emission ambition, it is obviously crucial to know the size of national carbon sequestration, so this is an important study.”

“However, although the forest reservoir is larger than previously thought, no one should mistake this as a form of ‘free pass’ to achieve zero emission. On the one hand, carbon absorption will be necessary to compensate for continuous emissions of all greenhouse gases, not just CO2; on the other hand, the carbon balance of China’s forests can be compromised by the impacts of climate change, as we are now seeing in places like California, Australia and Russia. ”