Ministerial Conference on
Environment and Development
in Asia and the Pacific 2000
Kitakyushu, Japan 31 August - 5 September 2000
|
|
|
Coral Reef Death in American Samoa American Samoa is caught in a whirl of environmental change. It's population is growing rapidly while natural resources are declining. Coral reefs in American Samoa were severely damaged in recent years by natural disasters and pollution. The reefs were hit with a major infestation of the coral eating starfish Acanthaster planci in the late 1970's and by devastating hurricanes in 1990 and 1991. More recently, the reefs experienced a major coral bleaching episode in March of 1994, which affected up to 80% of the remaining corals at some locations. As a result, live coral coverage around Tutuila Island dropped from about 60% to 10%. Along with this, there have been major changes in the species composition and abundance of reef fishes. In the past 14 years, the species composition of the 20 most abundant species has changed dramatically and fish numbers have dropped 75%. The 1994 subsistence catches of reef fish were the lowest on record. Some coral recovery is underway, but there are many human induced problems to recovery: 1. Sedimentation. After every heavy rainfall, chocolate colored plumes of sediment are flushed out of the streams and onto the coral reefs. 2. Eutrophication. Only about 10% of homes in American Samoa are hooked to a sewer line. An abundance of filamentous algae in nearshore waters indicates nutrient enrichment is another problem for the corals to deal with. 3. Pollution. Recent surveys discovered nearshore fish were contaminated with toxic substances, particularly heavy metals. 4. Overfishing. Some highly prized resources such as giant clams have been overharvested. One species is locally extinct and the other two are scarce. Several of American Samoa's government agencies have developed regulations, guidelines, and educational activities aimed at reducing these impacts. Despite the best efforts of these agencies, the reefs continue to decline. Deciding what happened to American Samoan corals is not simple. Hurricanes have been hitting the island for millions of years without significant long term damage - especially to deeper corals. Corals might, however, be weakened by sediment loading, pesticides and heavy metals in the sediments and overgrown by algae stimulated by nutrients in the sediment run-off. The corals might also be harmed by increased UV radiation when exposed at low tide. Elevated water temperature, possibly from global warming, complicates the picture still more. The coral eating starfish, the Crown of Thorns (Acanthaster planci) is another part of the puzzle. The controversy over the causes of population blooms of the crown of thorns starfish has gone on between scientists since the phenomenon was first noticed thirty years ago. These starfish digest the living tissues of reef building corals and have destroyed thousands of hectares of coral reefs around the tropical Pacific, starting in the early 1960's. Many scientists believed it was a cyclic event that would vanish on its own. But starfish infestations continue today (Gabriel et al 1995, Zann and Eager, 1987). Initial claims that outbreaks were common in pre-human reefs were shown to be incorrect (Keesing et. al. 1992). The starfish's impact on the coral reefs was self-evident. The interactions of the ocean's life systems that began the problem was not. Scientists have linked coral health to the abundance of fish populations that help supply corals with nutrients (Chesher 1972, 1979). Overfished reefs may have underfed corals that are less able to cope with environmental stress. Scientists at a workshop in Florida in 1991 concluded coral bleaching and death could be a product of pollution, and that regardless of global warming, coral reefs are already severely threatened by pollution and direct destruction (D'Elia, et al 1991). Coral reef decline is not easily defined by simple cause-effect relationships, the real answer is surely a combination of human-induced and natural stresses. There is only one sure way to treat the coral reefs: with greater care and respect. Some of the actions needed to protect the reefs from man-induced stress are reasonably simple changes in people's behavior, ranging from not deliberately breaking the coral to regulating fishing activities. More problematic, and perhaps more important, is reducing sewage, fertilizers, silt and toxins. Communities that depend on coral reef ecosystems would do well to adopt Agenda 21 procedures and think about what they would like the reefs to be like in the 21st century and then work out ways to accomplish this goal. See also: NOAA's Coral Reef Home Page at: Information and educational material on coral reefs and links to other coral reef sites at: http://ioc.unesco.org/iyo/classroom/classroom.htm Updates on tropical El Niņo developments are available on
the Internet through NOAA's Climate Prediction Center at: |
|
|