Islands have a special appeal – why else do visitors flock to tropical islands as places of idyll and escape. Islanders must exercise special care of their ecosystems which are fragile. Dr Anjani Ganase explains why islands are more vulnerable; and considers the delicate balance.
The definition of an island is a piece of land surrounded by water. There is an upper limit to how big islands can be; very large land masses, such as Australia, are considered continents. Usually, they are as small as the rocks we observe out at sea. The largest is Greenland, followed by New Guinea. Islands are mostly found in the ocean but can occur in lakes and rivers. The Orinoco River has several islands in its mouth formed by the sediment collected by the river. Consider the high-end New York neighbourhood of Manhattan that sits on an island in the Hudson River?
Islands are found everywhere around the world in all latitudes, but also at different elevations. In South America, there are five islands in Lake Titicaca at 3,000 metres above sea-level in the Andes. The local tribes there built many more artificial floating islands. While islands are home to some of the largest cities in the world, Tokyo, Japan and Jakarta, Indonesia, only the tiniest may be uninhabited. The most remote islands in the world are the Pitcairn islands, an overseas territory of the Great Britain, found in the southern Pacific. It has a population of 49 and the closest major land mass is New Zealand over 3,000 miles to its west. In the southern Atlantic, Tristan da Cunha, another remote overseas territory of Great Britain, indicates how far the reach of empire extended.
[caption id="attachment_891945" align="alignnone" width="1024"] Coral Caye, Belize. - ANJANI GANASE[/caption]
There are six major island types. The one we’re most familiar are continental islands, islands that sit offshore to continents but still located on the continental shelf. Trinidad and Tobago sits on the South American continental shelf with Tobago’s north east closest to the shelf’s edge. Coral islands are created from the growth of coral skeletons during the formation of coral reefs. Changes in sea level results in the exposure of the reef to form an island. Countries that are coral islands in the Caribbean include Bahamas and Turks and Caicos. Oceanic islands are islands born from submerged volcanoes that eventually breach the ocean’s surface. The Lesser Antilles are primarily oceanic islands forming an archipelago were the Caribbean plate meets the North American Plate. There are tidal islands, where erosion separates the island from the mainland and the low terrain between the two is submerged during high tides. Barrier islands lie parallel to the mainland coast and are typically formed because of the gathering of gravel and sediment by nearshore currents to form sand banks, or from sea-level rise that resulted in the formation of islands from sand dunes. Finally, artificial islands are those created by man. The most famous example of these is the palm tree islands of Dubai
