The first nature reserve in China was the Dinghushan Nature Reserve, established in 1956 near Zhaoqing City in Guangdong Province. The Sanjiangyuan Nature Reserve, which was established in August 2000, is the largest (316,000 sq km in area) nature reserve in China, with the highest elevation (over 4,000 m) and the richest biodiversity. It is located in the hinterland of the Qinghai-Tibet Plateau at the sources of the Yangtze, Yellow and Lancang rivers. By the end of 2001, 1,551 nature reserves of rather diversified types, covering a total area of 144.72 million ha (or 14.4 percent of China's land territory) had been established in China. They play important roles in water conservation, soil protection, wind and sand prevention, and the stabilization of the regional climate. Yunnan Province alone has more than 100 nature reserves, making it the province with the largest number of nature reserves in China. Twenty-one nature reserves—such as Wolong and Jiuzhaigou in Sichuan, Changbai Mountains in Jilin, Dinghuashan in Guangdong and Baishuijiang in Gansu—have been included on the World Biosphere Reserves list by the UNESCO.