66 Billion Trees: China’s Great Green Wall Behaves in an Unexpected Way

In the late 1970s, China embarked on a colossal reforestation campaign. New research reveals the unforeseen effects of tens of billions of trees planted along the edges of desert regions.

A meteoric growth

Most of them form the ‘Great Green Wall’ of China, a vegetative belt primarily aimed at curbing dust storms from the north. Located in southern China, another natural barrier that helps stabilize soils and limit the risks of natural disasters in this monsoon-affected region completes it.

Today, these artificial forests cover about 90 million hectares, more than a third of China’s total forested area. To clarify their environmental effects, researchers drew on a vast satellite data set and machine learning.

Overall, the vegetation cover of the new forests grew 3 to 4 times faster than that of their natural counterparts. This rapid growth is notably linked to their concentrations of young trees, whose more active metabolism promotes greater CO2 absorption.

Comparisons with natural forests of similar composition also showed that their vegetation cover remained on average 4.6% greater, suggesting that planting techniques and pre-site soil preparation play a significant role as well. The most striking differences were observed in mixed and conifer forests.

Refining our models

According to the study’s authors, published in the journal Geophysical Research Letters, this trend illustrates the remarkable adaptive capacity of certain trees to rising atmospheric CO2 levels.

At the same time, they emphasize the need not to treat the world’s forests as a single homogeneous entity in our models in order to assess more accurately their contribution to mitigating climate change.

Earlier this year, a study focusing on the portion of the Great Green Wall along the Taklamakan Desert suggested its transformation into a net carbon sink, absorbing 8.3 million tonnes of CO2 annually between 2004 and 2017, compared with 6.7 million tonnes emitted.