- Driven by the country’s rapid economic development in recent decades, especially urbanization, agricultural expansion, and reforestation, China has undergone large-scale changes in land use.
- According to the authors of the study, published earlier this month in the journal Science Advances, their results “highlight the importance of improving land-use management, especially in view of the recently proposed expansion of urban areas in China.”
- The researchers discovered large carbon losses resulted from China’s poor land management.
A new study examines the amount of carbon emissions created by land-use change and management practices in China, the second-largest economy and the largest carbon emitter in the world.
Driven by the country’s rapid economic development in recent decades, especially urbanization, agricultural expansion, and afforestation, China has undergone large-scale changes in land use. Yet, in the emissions reduction plan (known as an Intended Nationally Determined Contribution or INDC) submitted by the Chinese government ahead of the UN climate talks that lead to the Paris Climate Agreement last December, the country pledged to reach peak carbon emissions by 2030 and continue to draw down emissions thereafter. Reining in emissions from land-use change and poor land management is vital to meeting that target.
According to the authors of the study, published earlier this month in the journal Science Advances, their results “highlight the importance of improving land-use management, especially in view of the recently proposed expansion of urban areas in China.”
An international team of researchers led by Li Lai of Nanjing University analyzed shifts in China’s vegetation and soil carbon storage between 1990 and 2010 resulting from land-use conversion and management. They found that grasslands declined by 20.8 million hectares (or about 51.4 million acres), 6.9 percent of the country’s total. Meanwhile, urban areas increased 43.7 percent, or by about 6.87 million hectares (about 17 million acres); farmlands increased 0.84 percent, or about 1.48 million hectares (3.7 million acres); and forests increased 0.67 percent, or about 1.52 million hectares (3.8 million acres).
In addition to emissions from changes in land use, the researchers discovered large carbon losses resulted from China’s poor land management. “[L]and-use change not only directly reduces carbon storage in vegetation but also affects the amount of vegetation residues returned to the soil, which are, in turn, the main source of soil carbon storage,” they explain in the study.
Dr. Hong Yang of the University of Oslo in Norway, a co-author of the study, told Mongabay that the team’s “main finding is the failure of land use management,” particularly the Chinese government’s ineffective responses to forest fires, insect pests, and timber harvests. He added that this failure “is a new but previously ignored factor of carbon emissions in China from 1990 to 2010.”
Measures to control wildfires, pests, and diseases can have a significant impact on carbon storage, according to Dr. Yang and his colleagues. “For example: fires can directly release carbon from vegetation into the atmosphere; effective measures to control pests and diseases can help to avoid carbon emissions from dead plants; and proper fertilization and drainage can promote vegetation growth and may increase the accumulation of [soil organic carbon],” the researchers write in the study.
China’s total soil carbon pool suffered big losses due to the management problems identified in the study. Decreases in grassland areas with high carbon content in the soil resulted in emissions of about 11.5 teragams (Tg) per year between 1990 and 2010, the team found. Meanwhile, land-use management failures caused the emission of 101.8 Tg of carbon annually, contributing to an overall increase in China’s total emissions during that time period despite an increase in the biomass carbon pool due in part to China’s efforts to convert more land to forest, according to the study.
Together, land-use change and land-use management failures were responsible for a significant portion of China’s total emissions in the time period studied. “The combined effects of land-use category conversion and land-use management were large overall carbon emissions that totaled approximately 1.45 [petagrams (Pg)] of carbon between 1990 and 2010,” Dr. Yang said. “This equates to annual emissions of 72.4 Tg carbon per year, accounting for 15 percent of China’s total carbon emissions in 1990 and 4 percent in 2010.”
Compared to global averages, these amounts of emissions from land-use change are not actually that high. Researchers have previously estimated that land-use and land-cover change contributed one-third of all man-made carbon emissions emitted into Earth’s atmosphere since the industrial revolution, and were responsible for some 12.5 percent of total global emissions between 2000 and 2009, according to a 2010 study.
Additionally, there is some evidence, still inconclusive at this point, that China’s carbon emissions levels may have already peaked, more than a decade ahead of schedule. Still, there are cuts to emissions that can and should be made via more effective management of China’s land use, the researchers say.
Optimizing for carbon sequestration in land-use policies, particularly for forestland, grassland, and arable land, would go a long way, Dr. Yang suggests. “Policies should ensure that the quality of high-carbon land-use categories is maintained and should include monitoring to reduce the conversion from high-carbon to low-carbon land-use categories, such as deforestation and improper land reclamation in the black soil area of Northeast China,” he said.
“Measures should also be taken to limit the extension of urbanization into ecologically valuable land with high capacity for carbon storage (such as forest and grassland). Additional beneficial measures would include improved land-use management to reduce carbon emissions associated with management failures, particularly forest fires, pests, and illegal deforestation.”
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- Lai, L., Huang, X., Yang, H., Chuai, X., Zhang, M., Zhong, T., … & Thompson, J. R. (2016). Carbon emissions from land-use change and management in China between 1990 and 2010. Science Advances, 2(11). doi:10.1126/sciadv.1601063