Despite effective efforts to control desertification, China still faces a grave challenge, a senior official said on January 4.

A study conducted between 2005 and 2009 shows 2.62 million square km of Chinese land was degraded, said Zhu Lieke, deputy head of the State Forestry Administration, at a press conference.

Sand encroachment has affected 1.73 million square km of land, Zhu added.

The survey was China's fourth nationwide survey on land degradation and sand encroachment. Compared with results of the previous survey, the area of land degradation decreased 0.47 percent while that of sand encroachment fell 0.49 percent.

Still, in regions such as northwest Sichuan Province and the lower reaches of the Tarim River, China's longest inland waterway, in northwest China's Xinjiang Uygur Autonomous Region, the situation had deteriorated, Zhu said.