Island Ecosystems

An island is a body of land, smaller than a continent, completely surrounded by water. Plants and animals of island ecosystems have many distinctive features, often related to the type of island:

• old continental islands e.g. New Caledonia and New Zealand, originally part of a continent
• oceanic islands, generally volcanic and short lived e.g. Hawai'i
• coral atolls (see photo of Palmyra Atoll)
• small, numerous islands e.g. red mangrove islets in the tropics, sand islets of the Caribbean and Indian Ocean, and
• barrier islands parallel and close to the mainland coast.

Island ecosystems have been studied because they are simpler than ocean ecosystems. Even clusters of islands are simpler to study. Islands provide natural �experiments� for research because of their number, variation in shape, size, degree of isolation and ecology. Oceanic islands near continents may have continental plants and animals. More isolated islands may have endemic species. One of the key relationships in island biogeography is the area-biodiversity curve. Generally the larger the island, the more diverse the plants and animals. To put it another way, environmental diversity is correlated with island area.

More recent interest in island biogeography has had an impact on conservation biology. Many features of island ecosystems are relevant to ecosystem conservation elsewhere, on land as well as in the oceans. Island ecosystems have helped our understanding of:

• fragmentation (leading to insularization)
• creation of biotic communities, and
• species extinction.