Environmental issues in the Maldives include dwindling freshwater supply and inadequate sewage treatment. Recent estimates indicate that the nation's water supply may be exhausted in the near future, and population increases have created a sanitation problem that threatens the waters surrounding this island nation. Another significant environmental problem is a rise in sea levels due to global warming. The islands are particularly susceptible to flooding. Environmental preservation is complicated by the unique problems of a nation consisting of 1,200 islands spread over 510 miles of the Indian Ocean. Preservation of the desert island ecology, protection of marine life and coral reefs, and coconut tree rehabilitation are additional environmental goals. The hawksbill turtle, green turtle, and blue whale are on the endangered list.