In Mexico, 170,000 square kilometres (65,637 sq mi) are considered Protected Natural Areas. These include 34 biosphere reserves (unaltered ecosystems), 67 national parks, 4 natural monuments (protected in perpetuity for their aesthetic, scientific or historical value), 26 areas of protected flora and fauna, 4 areas for natural resource protection (conservation of soil, hydrological basins and forests) and 17 sanctuaries (zones rich in diverse species).