Tajikistan is nestled between Kyrgyzstan and Uzbekistan to the north and west, China to the east, and Afghanistan to the south. Mountains cover 93 percent of Tajikistan’s surface area. The two principal ranges, the Pamir Mountains and the Alay Mountains, give rise to many glacier-fed streams and rivers, which have been used to irrigate farmlands since ancient times. Central Asia’s other major mountain range, the Tian Shan, skirts northern Tajikistan. Mountainous terrain separates Tajikistan’s two population centers, which are in the lowlands of the southern Panj River and northern Fergana Valley sections of the country. Especially in areas of intensive agricultural and industrial activity, the Soviet Union’s natural resource utilization policies left independent Tajikistan with a legacy of environmental problems. With an area of 142,600 km2, Tajikistan has a maximum east-to-west extent is 700 km, and its maximum north-to-south extent is 350 km. The country’s highly irregular border is 3,651 km long, including 414 km along the Chinese border to the east and 1,206 km along the frontier with Afghanistan to the south. Most of the southern border with Afghanistan is set by the Amu Darya, darya is the Persian word for river and its tributary the Panj River, which has headwaters in Afghanistan and Tajikistan. The other neighbors are the former Soviet republics of Uzbekistan to the west and the north and Kyrgyzstan to the north.