Among Kyrgyzstan's most significant environmental issues are water pollution and soil salinity resulting from improper irrigation methods. The pollution of the nation's water causes health problems for 25% of its people, many of whom draw water directly from contaminated wells and streams. Only 66% of the nation's rural dwellers have a publicly regulated water supply. As of 2001, 3.5% of Kyrgyzstan's total land area is protected. In the same year, six mammal species and five species of birds were listed as threatened, as were seven plant species. Threatened animal species include the great bustard, European bison, snow leopard, field adder, and tiger.