China's 66 billion tree Great Green Wall grows faster than natural forests, study finds

A study in Geophysical Research Letters found that forests planted under China's Three-North Shelterbelt Program, also called the Great Green Wall, are increasing their leaf area faster than nearby natural forests. Since 1978, China has planted roughly 66 billion trees to slow desertification and reduce dust storms across northern China. Researchers from Peking University and Beijing Forestry University used satellite data to measure the Leaf Area Index (LAI), which estimates foliage density and photosynthetic activity. Planted forests expanded their leaf area 65.8% more rapidly than surrounding native forests. After adjusting for forest age and local conditions, the advantage remained at 4.6%, suggesting the faster growth is not just because the planted trees are younger. The study also found that denser canopies increase evapotranspiration, which raises local humidity and may trigger more rainfall. That feedback loop could help sustain forest growth. However, the planted forests are much younger than natural forests, so long-term conclusions remain cautious. The findings show that large-scale afforestation can influence ecosystem processes beyond simply adding tree cover.