A major environmental issue in China is the continued expansion of its deserts, particularly the Gobi Desert. Although barrier tree lines planted since the 1970s have reduced the frequency of sandstorms, prolonged drought and poor agricultural practices have resulted in dust storms plaguing northern China each spring, which then spread to other parts of East Asia, including Japan and Korea. China's environmental watchdog, SEPA, stated in 2007 that China is losing per year to desertification. Water quality, erosion, and pollution control have become important issues in China's relations with other countries. Melting glaciers in the Himalayas could potentially lead to water shortages for hundreds of millions of people.