People have called the Big Thicket an American ark and the biological crossroads of North America. The preserve was established to protect its complex biological diversity. What is extraordinary is not the rarity or abundance of its life forms, but how many species coexist here. Once vast, this combination of pine and cypress forest, hardwood forest, meadow and blackwater swamp is but a remnant. With such varied habitats, "Big Thicket" is a misnomer, but it seems appropriate.A convergence of ecosystems occurred here during the last Ice Age. It brought together, in one geographical location, the eastern hardwood forests, the Gulf coastal plains, and the midwest prairies.The Preserve consists of nine land units and six water corridors encompassing more than 97,000 acres. On December 15, 1981, the Preserve was designated an International Biosphere Reserve by the United Nations Education, Scientific and Cultural Organization (UNESCO) Man and the Biosphere Program. On July 26, 2001, the American Bird Conservancy recognized the Preserve as a Globally Important Bird Area joining thousands of others around the world.