China is fighting a war against its deserts, which are expanding and joining to create a massive dustbowl.
It is a battle which is being waged in places where human habitation is scarce.
But its success or failure will have environmental implications thousands of kilometres away.
I drove 2,000km through China's largest desert - the Taklamakan in north-western Xinjiang province - to see what was being done.
Two thousand years ago, the ancient Chinese called the Taklamakan desert the Moving Sands.
And their secrets lie buried in its depths - around 300 ancient cities swallowed by this sea of sand.
Even today, life is a constant struggle for those living on the edges of China's deserts.
They are people like farmer Imin Barat. The sand dunes are literally on his doorstep, and every year they creep closer.
"The sand is burying the houses, so we've had to rebuild them. It's also burying our crops," he said.
"By the time someone gets to 60 years old around here, they'll have had to move house three or four times on average."
Imin Barat checked his precious herd of sheep. They are the main source of income for his family of eight, who have already lost two houses to the encroaching sands.
But the irony is that herdsmen like Mr Barat are actually helping the desert advance.
Their animals eat the plants which keep it in check.
After the communists came to power in 1949, they resettled three million people in far flung Xinjiang.
Their role is to populate the barren wasteland, protect the borders and dilute the restive local Uighur population. But the mass migration brought over ploughing and overgrazing, making the desert spread even faster.
"Desertification and soil erosion is a huge issue in China and it is absolutely of global significance," said Juergen Voegele, an expert on desertification at the World Bank in Beijing.
"China is one of the countries in the world with the highest soil erosion rates anywhere. If you look at the numbers you can say that about.... one quarter of the total land area in this country is in the process of active desertification and a large portion of that is actually irreversible, so we're not talking about a small problem.
"We're talking about a very big problem which not only has consequences domestically, but also in the region," he said.
And those consequences can be seen each Spring when sandstorms darken the skies of China's eastern cities, thousands of kilometres away.
Dust from China's western deserts even reach as far afield as Japan and South Korea.
The sandstorms have been a wake-up call that the problem needs to be tackled, and urgently.
To show what is being done we were taken to a plant research centre in the desert funded by the local Tarim oil company.
It is a tiny spot of green amid a huge expanse of yellow sand.
"We need to find plants that don't need a lot of water," said botanist Liu Bujun.
And as we drive down the never-ending desert highway, it is clear that action is being taken to prevent the road being inundated, protecting important commercial interests.
But much more still has to be done, according to Mr Voegele.
"The government is taking the issue seriously. I do still think not seriously enough. They are looking at policies individually not comprehensively.
"There is a large tree planting campaign going on for instance, which is helpful, but by itself it will not solve the problem. If it's not combined with better grazing management policies at the same time, those trees will not survive," he said.
Deep into the desert we suddenly come across a small band of workers digging for water by the side of the road.
"We're digging a well," their foreman said. "We're making this place green. In five years, there'll be red willow, poplars and date trees growing here. It'll be the longest green corridor in the world."
It is a bold - you might say, crazy - statement from a man surrounded by rolling sand dunes. But China needs to take bold steps, and soon, to stop its moving sand.