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The vast region of the Pacific Ocean collectively called Oceania holds thousands of islands. Oceania spreads across the Pacific from 20 degrees north latitude to 50 degrees south latitude and from longitude 125 degrees east to 130 degrees west. The major groupings of islands are Melanesia, Micronesia, Polynesia, and New Zealand. Melanesia ("black islands") is a group of large islands immediately north and east of Australia, from New Guinea to New Caledonia. Micronesia ("little islands") is made up of hundreds of tiny atolls in the western Pacific. Polynesia a huge region in the central Pacific. New Zealand lies east and south of Australia. For botanical purposes, these islands can be categorized by climate and formation type. Climates range from tropical to sub Antarctic, dry to very rainy. Types include volcanic (Fiji, Guam, and Hawaii), tectonic (New Zealand and New Guinea), and low coral atolls (nearly all of Micronesia's islands).
Unique Ecosystems
Organisms have a hard time reaching islands across the broad expanses of the Pacific Ocean. The islands' isolation leads to trends in the number of species on any given island. Bigger islands have more species; those farthest from continents have fewer species. To reach the islands, plants must be carried by animals or rely on wind or water currents. Birds are usually the first visitors, bringing with them hitchhiking insects and plant seeds in their digestive tracts.
Island plants and animals evolve together, affected by difficult conditions. Soil is often poor and food limited. Harsh environments and isolation contribute to the formation of new and unique species. Island ecosystems are sensitive to disturbances, whether from natural causes, such as severe storms, or human activities, such as construction, agriculture, logging, and introduced species.
Introduced species (exotics), both accidental and deliberate, are a serious problem. Rats and feral animals (domestic animals that have gone wild) can devastate island ecosystems. Pigs, rats, and goats are particularly devastating to vegetation. Introduced plants may overgrow native ones. Exotics also bring diseases or other problems to which native plants and animals have no resistance. For example, a Hawaiian bee crawls headfirst into native, barrel-shaped flowers, gathers the nectar, and then backs out. A plant that was introduced in Hawaii by landscapers attracted bees, but the flowers were smaller than those of the native plants. Once a bee crawled in, it became stuck like a cork in a bottle. This led to thousands of these plants, each with hundreds of flowers, becoming stoppered with dead bees.
Many tropical and temperate islands have coastal wetlands and mangrove swamps growing at the edge of the sea. Mangroves are low-growing, salt-tolerant trees that form dense tangles virtually impenetrable to humans. Wetlands and mangrove swamps are important breeding grounds for many types of fish and crabs and also trap sediment, stabilize shorelines, and protect coastlines from storms. When humans fill in the wetlands and cut down the mangroves, it causes coastal erosion and the loss of food fish.
Fiji Islands
The Fiji Islands are mostly volcanic in origin and lie in the South Pacific Ocean between longitudes 175 degrees east and 178 degrees west and 15 degrees and 22 degrees south latitudes, about 1,300 miles (2,100 kilometers) north of Auckland.
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New Guinea
The world's largest tropical island, New Guinea is located north of Australia, just south of the equator.
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New Zealand
Located off the eastern edge of Australia, New Zealand has a fairly moderate climate that comes from conflicting warm, humid Pacific and colder Antarctic weather.
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Coral Atolls
The Federated States of Micronesia consist mainly of small atolls. Coral atolls are found only in tropical latitudes because coral (small, colonial animals) grow only in warm water.
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Future Prospects
Island ecosystems are unique and fragile. Some, like those in Guam and New Zealand, can never be returned to their original state, but with extensive wildlife management, many native species can be saved from extinction.
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