But human activity has troubled the ocean's health. Many fish species have been harvested to the point that their populations are threatened. The coastal mangrove forests of Asia have been destroyed by shrimp farming. The habitats of marine mammals and fish have been degraded severely, with pollution, responsible for the mass death of fish, mammals and corals. Several coastal areas have witnessed shellfish poisoning. Organochlorine pollutants, pesticides, polychlorinated biphenyls and a range of other pollutants accummulate within fishes later moving up the food chain to cause reproductive disorders. Climate changes have also endangered marine species. If the invaluable resources from the oceans are to be conserved, then humankind has its job cut out in the coming millennium.