Photo taken on Sept. 24, 2011 shows villager Wang Lanying herd cattle on the riverbed of China's largest desert lake Hongjiannao in Yulin, north China's Shaanxi Province. Hongjiannao is shrinking as a result of climate change and human activities, and may vanish in a few decades. Its lake area, which measured more than 6,700 hectares in 1996, has shrunk to 4,180 hectares. Its water level is declining by 20-30 centimeters annually and its water PH value has risen to 9.0-9.42 from 7.4-7.8.