The People’s Republic of China is the second-largest country in the world by land area after Russia, and is either the third- or fourth-largest by total area, after Russia, Canada and, depending on the definition of total area, the United States. China’s total area is generally stated as being approximately 9,600,000 km2 (3,700,000 sq mi). Specific area figures range from 9,572,900 km2 (3,696,100 sq mi) according to the Encyclopædia Britannica, 9,596,961 km2 (3,705,407 sq mi) according to the UN Demographic Yearbook, to 9,596,961 km2 (3,705,407 sq mi) according to the CIA World Factbook.
China has the longest combined land border in the world, measuring 22,117 km (13,743 mi) from the mouth of the Yalu River to the Gulf of Tonkin. China borders 14 nations, more than any other country except Russia, which also borders 14. China extends across much of East Asia, bordering Vietnam, Laos, and Myanmar (Burma) in Southeast Asia; India, Bhutan, Nepal, Afghanistan, and Pakistan[q] in South Asia; Tajikistan, Kyrgyzstan and Kazakhstan in Central Asia; and Russia, Mongolia, and North Korea in Inner Asia and Northeast Asia. Additionally, China shares maritime boundaries with South Korea, Japan, Vietnam, and the Philippines.
China’s climate is mainly dominated by dry seasons and wet monsoons, which lead to pronounced temperature differences between winter and summer. In the winter, northern winds coming from high-latitude areas are cold and dry; in summer, southern winds from coastal areas at lower latitudes are warm and moist. The climate in China differs from region to region because of the country’s highly complex topography.
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 Korea and Japan. China’s environmental watchdog, SEPA, stated in 2007 that China is losing a million acres (4,000 km²) 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.