Guam is surrounded by approximately 110 square km of shallow coral reefs, with an additional 110 acres occuring in offshore waters. Much of Guam is surrounding by a fringing reef, but the island also possesses patch reefs, shallow and deep lagoonal reefs, submerged banks, and other reef types. Guam's reefs are home to over 5,000 known marine organisms, with likely many thousands more awaiting discovery. Many of Guam's reefs, however, are under assault by numerous threats - mostly local threats caused by people living on the island. Guam's terrestrial environment is fairing even worse, with the loss of most of the native bird species as a result of the invasive brown tree snake, the replacement of native plants by introduced species, and intense development pressure on the remaining developeable land. Still, Guam is a beautiful island, with hidden natural treasures awaiting those willing to seek them out.