The southwest contains most of the people, and villages are densely clustered with little unused land. In the Central Highlands around Kandy, villagers faced with limited flat land have developed intricately terraced hillsides where they grow rice. In the 1960s and 1970s, the wet cultivation area was expanding rapidly, as the government implemented large-scale irrigation projects to restore the dry zone to agricultural productivity. In the 1970s, the area drained by the Mahaweli Ganga changed from a sparsely inhabited region to a wet rice area similar to the southwest. Through such projects, the government of Sri Lanka has planned to recreate in the dry zone the lush, landscape associated with the irrigation works in ancient Sri Lanka. Beginning in the 16th century and culminating during the British rule of the 19th and 20th centuries, the plantation economy came to dominate large sections of the highlands. Plantation farming resulted in a drastic reduction in the natural forest cover and the substitution of domesticated crops, such as rubber, tea, or cinnamon. It also brought about a changed life-style, as the last hunting-and-gathering societies retreated into smaller areas and laborers moved into the highlands to work on plantations. Through the late 20th century, workers on large plantations lived in villages of small houses or in "line rooms" containing ten to twelve units. The numerous plantations of small landholders frequently included attached hamlets of workers in addition to the independent houses of the plantation owners. The coastal belt surrounding the island contains a different settlement pattern that has evolved from older fishing villages. Separate fishing settlements expanded laterally along the coast, linked by a coastal highway and a railway. The mobility of the coastal population during colonial times and after independence led to an increase in the size and number of villages, as well as to the development of growing urban centers with outside contacts. In the 1980s, it was possible to drive for many kilometers along the southwest coast without finding a break in the string of villages and bazaar centers merging into each other and into towns. Statistics Land use (2018): 20.7% arable land, 15.8% permanent crops, 7% permanent pasture, 29.4% forest, 27.1% other. Irrigated land: 5,700 km2 (2012) Total renewable water resources: 52.8 cubic km Natural hazards: occasional cyclones and tornadoes Environmental issues: deforestation; soil erosion; wildlife populations threatened by poaching and urbanization; coastal degradation from mining activities and increased pollution;