Question

Why there is more biodiversity on continent than in island?

Answer 1

An explanation of island biodiversity should start with a definition of islands. Yet this definition is elusive. Although we can all agree that an island, strictly speaking, is a piece of land surrounded by water, beyond this stiupulation, there is no single accepted definition. The Millennium Ecosystem Assessment, for example, defines islands as “lands isolated by surrounding water and with a high proportion of coast to hinterland”; stipulates that they must be populated, separated from the mainland by a distance of at least two kilometres, and measure between 0.15 square kilometres and the size of Greenland (2.2 million square kilometres). 

Answer 2

An explanation of island biodiversity should start with a definition of islands. Yet this definition is elusive. Although we can all agree that an island, strictly speaking, is a piece of land surrounded by water, beyond this stiupulation, there is no single accepted definition. The Millennium Ecosystem Assessment, for example, defines islands as “lands isolated by surrounding water and with a high proportion of coast to hinterland”; stipulates that they must be populated, separated from the mainland by a distance of at least two kilometres, and measure between 0.15 square kilometres and the size of Greenland (2.2 million square kilometres). Islands located within seas can be categorized in many ways, including by their area; by their altitude into high and low-lying islands; by a combination of the size of the land area, and political and demographic criteria to identify small island developing States; by their distance from the nearest continent; whether there are inhabited or not; the number of inhabitants; or whether they are continental (land areas that used to be connected to the mainland) or oceanic (those that rose from the sea as a result of coral deposits, volcanic activity or tectonic forces) islands. At the SCBD, work on island biodiversity emphasizes oceanic islands and particularly small island developing States (SIDS) because these systems are often perceived to be the most at risk.