GHLands:A new Chinese study has found that the country's "Great Green Wall" project, under which nearly 66 billion trees have been planted over several decades, has significantly enhanced the growth of planted forests, increasing their capacity to absorb carbon during the early stages of development and strengthening their role in combating climate change.
The study, published in the journal Geophysical Research Letters, found that forests established under the large-scale afforestation project are experiencing substantially faster increases in leaf area than natural forests. Leaf area is considered a key indicator of photosynthetic activity, forest productivity, and carbon storage capacity.
Faster Growth and Greater Carbon Sequestration
Researchers based their analysis on the Leaf Area Index (LAI), a widely used measure that estimates the total leaf surface area relative to the ground area it covers. The index is commonly used to assess forest productivity and the ability of vegetation to absorb carbon dioxide through photosynthesis.
The findings showed that the leaf area of planted forests increased 65.8% faster than that of natural forests across China.
To ensure the results were not simply driven by differences in age or environmental conditions, the researchers applied a statistical method known as Propensity Score Matching (PSM) to compare forests with similar characteristics. Even after controlling for these factors, planted forests maintained a growth advantage of 4.6% over natural forests.
The study also found that this advantage was most pronounced in mixed and evergreen forests, where planted trees demonstrated a stronger response to rising atmospheric carbon dioxide concentrations.
Growth Advantage Declines as Forests Mature
Despite the positive findings, the study noted that the growth advantage of planted forests is not permanent. It begins to diminish once trees reach approximately 40 years of age.
As forests mature, natural forests gradually become more effective at increasing their leaf area and eventually outperform planted forests in age-related growth.
According to the researchers, the early advantage of planted forests can largely be attributed to two factors: their younger average age—approximately 34 years, compared with 57 years for natural forests—and their greater sensitivity to elevated atmospheric carbon dioxide levels, which stimulates faster growth during the first decades of development.
Study Highlights the Importance of Balanced Forest Management
The researchers said the findings underscore the value of large-scale afforestation programs in enhancing forests' ability to sequester carbon and mitigate the effects of climate change, particularly during the early stages of forest growth.
At the same time, they emphasized that natural forests remain indispensable over the long term because their ecological performance improves as they mature. The study therefore recommends forest management strategies that combine continued afforestation with the conservation of existing natural forests, rather than relying exclusively on either approach.
The researchers added that the findings could help improve scientific models used to predict the role of forests in the global carbon cycle, contributing to more accurate climate projections and more effective strategies for addressing climate change.
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