Inside the domed gates of the Baijitan project, we drove through the small village that houses the project's workforce, then along a gravel road lined with silver green poplars and fruit trees neatly planted in rows and squares. Beyond the trees are fields planted with crops. Ten years ago this was all desert says Mr. Wang. Eventually the cultivated area gives way to scrubland planted with young trees, then to sand dunes. In the distance is a low mountain range, marking the edge of the gravelly desert known in China as gebitan and in the west as Gobi desert.

A couple of kilometers out in the sand dunes, bulldozers are carving out a new road and workers are laying networks of grass squares and planting shrubs. But walk five minutes away from the bustle and noise and the calls of small birds and the buzzing of bees seem to perfect, rather than disturb, the silence; one can almost hear the beating of the wings of the white butterflies fluttering among the sparse vegetation.

The Baijitan conservation area has an area of 1.48 million mu (9,866 hectares; 15 mu = 1 hectare). Every year its workers lay 20,000 mu (1333 hectares) of grass squares. Mr. Wang told us the project operates all the year round apart from a short break in winter when the weather makes work impossible.

The project was initially set up by the central government in 1953 as a sand control research institute. Mr. Wang told us that the state's concerns were initially practical and focused on the economy; to prevent erosion exacerbating the silting problem of the Yellow River, to protect nearby roads, railways and croplands from erosion and desertification. Later, the government's aims expanded to include concern for the environment per se, and when the Baijitan conservation project was established as a successor to the sand control institute in 2000, preserving endangered species was one of its main goals. The conservation area now supports 111 animal species and 306 species of plants.