One of the most significant environmental problems in Guinea-Bissau is fire, which destroys 40,000 ha of land per year and accelerates the loss of the nation's forests at a yearly rate of about 220 sq mi. In addition, Guinea-Bissau had lost over 75% of its original mangrove areas by the mid-1980s, with the remaining swamps covering 236,000 hectares. Only about 79% of city dwellers and 49% of the people living in rural areas have access to pure drinking water. The nation has 16 cu km of renewable water resources, with 36% used for farming activity. Only 46% of the population have adequate sanitation. Another environmental issue is soil damage, caused by drought and erosion, as well as acidification and salinization. The Ministry of Natural Resources, created in January 1979, is responsible for making and enforcing environmental policy. Of Guinea-Bissau's 108 species of mammals, 4 are endangered, as are 1 of 243 bird species and 3 types of reptiles. Threatened species include the Pygmy hippopotamus and the West African manatee.