China’s Great Green Wall trees grow faster but store less carbon long-term

China’s expansive reforestation initiative, known formally as the Three-North Shelter Forest Program, has reached a point of both documented success and significant scientific uncertainty. Since its inception in 1978, the country has planted 66 billion trees in an effort to combat the expansion of the Gobi and Taklamakan deserts. This “Great Green Wall” is currently slated for completion in 2050.

The project, which seeks to stabilize land threatened by sandstorms and desertification, has seen the region’s forest cover increase from 5 percent in 1978 to 14 percent in 2023. By November 2024, officials reported the completion of a 3,046-kilometer green belt encircling the Taklamakan Desert, utilizing species such as desert poplar, sacsaoul, and red willow. These efforts have yielded measurable environmental benefits, including improved air quality in downwind cities like Beijing and the creation of a carbon sink in previously barren fringe zones where seasonal rainfall of approximately 16.3 millimeters allows for periodic photosynthesis.

Despite these achievements, a study published in Geophysical Research Letters highlights a complex reality regarding the project's long-term environmental role. Researchers found that trees within the man-made forest grow 66 percent faster in leaf area than their natural counterparts. When comparing trees of similar age and conditions, the planted forests still showed a 4.6 percent faster growth rate. Yuhang Luo, a landscape ecologist at Peking University in Shenzhen, suggests this accelerated growth may be a response to rising atmospheric CO2 levels, though the exact mechanisms remain under investigation.

This rapid growth, however, comes with a caveat. The study notes that the performance of these trees peaks when they are between 30 and 40 years old, followed by a sharp decline. While natural forests exhibit slower, steady development, they appear to offer greater resilience and superior capacity for long-term carbon sequestration.

"Planted forests can be a powerful short-term tool for carbon uptake, but this advantage is temporary. For long-term carbon storage and resilience, natural forests remain irreplaceable."

Yuhang Luo, landscape ecologist at Peking University, via Live Science

The project also faces structural challenges that critics have highlighted over several decades. Because much of the wall consists of monoculture plantings, such as poplar and willow, the forests are vulnerable to disease; for example, one billion poplar trees were lost to a single pathogen in the Ningxia province in 2000. Furthermore, the reliance on human intervention to maintain trees in hyperarid environments has raised concerns regarding water sustainability. Xian Xue of the Chinese Academy of Sciences has previously warned that planting trees in areas without sufficient natural water supplies can lower the groundwater table, potentially accelerating desertification in some sectors.

While some researchers point to a reduction in sandstorm frequency, others attribute this trend to broader climatic factors rather than the shelterbelt itself. Ongoing research confirms that while ecosystem services have generally improved, issues such as aging forest stands, species homogenization, and declining ecological functions persist.