China's 66 billion planted trees are growing 66% faster than natural forests.
For nearly 50 years, China has been building the world's largest reforestation project, known as the Great Green Wall. Stretching across the edges of the Gobi and Taklamakan deserts, the massive belt of trees was designed to slow the spread of desertification.
Now, a new study suggests those planted forests are behaving differently than natural ones.
Using satellite observations, researchers found that the planted forests have been increasing their leaf area about 66% faster than nearby natural forests.
Part of the reason is simple: younger trees naturally grow faster than older ones. The planted forests are also actively managed by people.
But even after accounting for differences in age and growing conditions, the researchers found the planted forests were still growing about 4.6% faster than comparable natural forests.
Scientists think one reason may be that these younger forests are responding more strongly to rising carbon dioxide levels in Earth's atmosphere, though exactly why remains unclear.
The findings could improve how scientists estimate how much carbon forests remove from the atmosphere.
There is an important catch, however.
The study found the growth advantage peaks when the trees are around 30 to 40 years old before beginning to fade. Natural forests grow more slowly, but they continue storing carbon for much longer and support far greater biodiversity.
That means planting trees can be an effective short-term way to capture carbon, but researchers say it is not a replacement for protecting existing forests.
China's Great Green Wall has already increased forest cover across the region from about 5% in 1978 to 14% in 2023, helping reduce dust storms and improve air quality.
Now scientists are discovering that the project may also be teaching us new lessons about how forests respond to a changing climate.
Learn more:
"Enhanced CO2 Response and Aging-Related Dynamics Drive a Greater Leaf Area Index Increase in China's Planted Forests in Comparison to Natural Forests." Geophysical Research Letters.