LHASA, July 29 -- The ecosystem of Tibet Autonomous Region in southwest China has been in a good condition, a senior official with local government said Saturday.The air and water quality in Tibet has ranked the best among other areas across China, and the primeval forests in Tibet have been well preserved, said Hao Peng, vice chairman of the Tibet Autonomous Region.Environmental protection is a prime task for Tibet. Legislation, law enforcement and education among the public have been reinforced to protect the region's biological system, Hao told a group of foreign journalists who were making a reporting trip in Tibet.More than 400,000 square km of land in Tibet has been designated as nature reserves under autonomous regional or national protection lists, accounting for 30 percent of the region's total territorial acreage.More projects have been launched to retrieve forests and grasslands from farmlands and pastures. Large-scale afforestation campaign has also contributed to the growth of the green coverage in the region, Hao said.