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Tree planting in China – a panacea for carbon and desertification?
by Tristan Edmondson
In 122 BC the Chinese naturalist Liu An attempted to make Daoism China’s state religion, which has a harmonious approach to nature close to what we might call sustainability today. Liu An failed to oust Confucianism, but we can be sure that he would disapprove of modern day China’s Great Green Wall, the world’s largest tree-planting programme and an attempt to increase forest cover from 5% to 15% in China’s semi-arid north-western regions.
The Green Wall has ostensibly been a success story – since 1978 36.5 million hectares has been planted, mostly with a hybrid Poplar tree. Stretching 1,700 miles, this enormous belt of vegetation is meant to be a barrier to the encroaching deserts and holding down the dust storms that blight northern China and north-east Asia. However, scientific consensus in China is highly critical of the project and some claim it has done more harm than good.
Jiang Gaoming, professor at the Chinese Academy of Sciences’ Institute of Botany and vice secretary-general of the China Society of Biological Conservation, says that northern China is not suitable for tree planting, and that the Green Wall violates basic ecological principles. Jiang’s doubts over the efficacy of tree planting stem from the fact that this region has been treeless for thousands of years. Northwest China’s natural vegetation is shrub and grass which are adapted to low levels of precipitation.
Poplars planted in semi-arid regions initially grow fast, but this thirsty tree sucks up groundwater that has taken years to accumulate. When the water is gone, the trees die or become stunted. A 2006 study by researchers from the Chinese Academy of Sciences, Beijing Forestry University, the University of Toledo and USDA Forest Service and showed how poplar trees planted in the Kubuqi desert in Inner Mongolia raised the ratio of evapotranspiration to rainfall by 50% in comparison with natural shrub vegetation.
This rapid depletion of groundwater results in an increased rate of desertification and a lack of natural shrubs to anchor the top soil, often causing more dust storms. Gao Yuchan of Shaanxi province’s forestry bureau believes that enclosure is the best way to restore natural vegetation that can prevent desertification and reduce dust storms. He claims that “planting trees for 10 years is not as effective as enclosure for one year”.
Cao Shixiong, an associate professor at Beijing Forestry University, says that of the billions of trees planted in arid and semi-arid areas since 1978 in the Three Norths Project, only 15% remain alive today.