In rural China, the earth is moving, literally. A society based on agriculture is now attempting to undo centuries of environmental abuse - land erosion, desertification and climatic shifts - by planting trees across vast tracts of land. The Sloped Land Conversion Project, also known as 'trading crops for forests', contracts farmers to plant trees on slopes which are relatively unsuitable for farming. To offset the loss of income, farmers are compensated in grain and cash subsidies. Seeing potential for non-farm employment, such as a job in the city or raising livestock in addition to the subsidies, farmers have generally responded favourably. Local governments, hungry for state funds, have signed on to the project at a rate that has exceeded expectations and placed pressure on the central government to expand the campaign. Since 1999, the project has converted more than 4 million hectares of farmland and barren land to forest, and the government recently expanded the project to 25 provinces. The response should be good news for environmentalists. Yet it raises questions as to who, if anyone, is profiting from the programme. Both farmers and the environment may lose more than they gain. The danger of government manipulation of the farming population, which numbers nearly 250 million, is that once subsidies run out, the massive environmental engineering project may uproot itself. The driving force behind the project is money, and the bad news is that money, just like land, is a limited resource. A study of farmers in several regions by the Chinese Academy of Sciences concludes that land conversion typically leads to a drop in income, which is barely compensated for by the subsidy. Despite some movement towards jobs away from farms, after a three-year pilot period, participants were still tied to the land. The government has until 2008 - when the subsidy period expires - to make the programme sustainable. Sustainability is a challenge when the project is being hijacked by incompetent, corrupt local administrations. Han Chengjin, a participating farmer from Shandong province, illustrates the gap between policy and practice. He has planted trees for paper on flat, not sloped land. The closest thing to a subsidy he has received is a government loan of saplings valued at 3,000 yuan, to be paid back after the first harvest. Fortunately, while the trees grow, he has time to earn money for his family collecting recyclable goods in the city. He is dimly hopeful that he will eventually be able to sell the trees at market price. But he knows government promises are often empty. 'The policy is a good one,' he said. 'But when it gets to the local administration, it changes.' Human manipulation of the environment may prove similarly counterproductive. Farmers and local officials are not environmental engineers, so in selecting land to convert, they consider economics, not ecology. The result, say experts, is a high rate of conversion of land near roads or which is relatively flat, while it is steeply sloping land that most needs trees to stem erosion. China cannot permanently turn land to forest without complementary economic restructuring to strengthen non-agricultural employment opportunities. Easing household registration regulations would foster crucial labour migration into cities. As China's agricultural tradition yields to the forces of modernisation, tensions abound: time is working against efforts to salvage the deteriorating ecosystem, and the desire to taste the fruits of capitalism chafes against the bitterness of farm labour. The land conversion project is a well-intentioned effort to make environmental policy a fair deal both for the Earth and its inhabitants. But plugging loopholes with subsidies ensures that once artificial incentives run out, farmers will plunge further into poverty, or simply return to tilling the land. Michelle Chen is an American Fulbright researcher based in Shanghai