How to Fight a Desert: China’s War on Sand

Originally from Sketchy Science.

 Beijing is a pretty important place. China’s capital and largest city is not only home to over 21 million people, it is the seat of power for the world’s most rapidly developing country. Consider the fact that over the past three years, China has used more concrete than the United States in the entire 20th century and you can begin to understand how quickly the world’s most populous country is catching up to the west.

 All that development comes at a cost, however; and since the late 70’s Chinese officials have been hard at work fighting what they call the yellow dragon and the rest of us call the Gobi Desert. You see, overgrazing, deforestation, and drought throughout China have caused soils to erode and blow away, leading to the advancement of the Gobi and an intensification of the annual dust storms that pound Beijing and bring Asian dust particles (as well as pollution) across oceans to the west coast of North America.

This environmental degradation is not unheard of. Most people are familiar with the dust bowl that devoured over 4 million acres of the North American plains in the early 20th century. Those conditions were cause by exactly the same behaviours that have created the problems in China. Too many cows eating all the grass, the grass dying because of drought, top soil destabilizing because there are no plant roots to hold it all in place, and all of it blowing away with disastrous consequences.

So what can be done to stop a desert once it gets to marching? In the US the answer came in the form of a 100 mile (160 km) wide strip of trees running north to south through the country which reduced the amount of dust in the air by 60% in a few years. Since the 1970’s, China has been hard at work building a forest of their own, the Green Wall of China.

The scale of the Chinese reforestation effort boggles the mind. While the UN estimates that only 2% of China’s natural forests remain intact, the country plans to plant enough trees to increase its forest cover to 42% by 2050. Over the past ten years alone, Chinese citizens have planted over 56 billion trees. Each year they plant twice as many trees as the rest of the world combined. So, is it working?

The results, it turns out, have been mixed. While China is now approximately 20% forest-covered those forests aren’t exactly as natured intended. Apparently planters in the north have relied almost exclusively on poplar trees, people in the south have planted firs, and elsewhere forests are almost entire eucalyptus. The practice of planting only one kind of tree is called monoculture, and it is very risky business.

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A forest with only one kind of tree has a lot of the same problems as a baseball team where everyone is a right-handed batter. In the short-run they might win a few games but eventually they will come up against a left-handed pitcher and thing will fall apart as we saw in our discussion of left-handed people. Likewise a monocultured forest might look alright at a glance but if a disease finds its way in which effects one of the trees, it is likely to take them all down at once. This is exactly what happened in Ningxia in northwest China when in 2000 a pest wiped out over a billion trees representing two decades of planting.

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Monocultures aren’t the only problem facing the green wall. While the wall of poplars protecting Beijing seemed like a great idea when it was created because of the fast growth rate and toughness of the trees, they are now dying off because they were all grown from cuttings, which have a shorter lifespan than trees grown from seeds (30 to 40 years versus several hundred).  

A solution to the problem might, ironically, lie in a plant that China devoted much of its energy to eliminating in the 80’s and 90’s called sea-buckthorn. Buckthorn is a shrubby bush that grows along river banks and was previously thought of as a pest because its root systems burrow deeply into soil and are almost impossible to remove. That is a perfect trait for battling a desert. Mixed forests of sea-buckthorn and poplar have already shown a lot more promise than poplar forests alone. It turns out that using China’s native trees rather than ones chosen by planters might be the smarter way to go about things.

Reforesting China is not going to be easy. The northern part of the country is a lot more arid than places with successful reforestation campaigns like the US, Germany, and Siberia. In order to stabilize the Gobi, China will have to learn quickly that the solutions to its problems are more likely to be found along its own river banks and in its remaining natural forests than in the policies of other nations.