Kueffer, C., Drake, D. Fernandez-Palacios, J M. 2016. Island Biology. In: Oxford Bibliographies in Ecology. DOI: 10.1093/OBO/9780199830060-0149.
This article focuses on the ecology, evolutionary biology, and conservation of biotas on islands surrounded by ocean. These include oceanic islands in a strict sense (i.e., volcanic islands), atolls, islands on a continental shelf, and continental fragments (i.e., islands that originated from a continental plate but are now isolated in the ocean). This article treats only the terrestrial ecology of islands, and it does not cover islands in freshwater bodies, or islandlike isolated habitats on land such as mountaintops or landscape fragments. Islands can be found in all oceans of the planet and at all latitudes and consequently in all climate zones. They are characterized by their small area and isolation from other land, although both isolation and land area vary very widely. In this article we focus mostly on islands that are fully and continuously detached from the mainland and especially treat land-bridge islands (e.g., British Isles) only marginally. Islands are often part of island groups or chains, but they can also be completely isolated. Some islands reach an elevation of several thousand meters above sea level and then share many characteristics with mountains, including elevational vegetation zonation and often strongly contrasting leeward and windward climates. There are at least twenty thousand islands more than one square kilometer in area and millions if all sizes are considered. Together they make up nearly 5.3 percent of the earth’s land area. Island biodiversity is of huge importance for global biodiversity because of its high endemism. For instance, about one quarter of vascular plant diversity is endemic to islands. Oceanic islands have long been used as model systems for research in biogeography, ecology, evolution, and conservation. Islands were crucial for the formulation of Charles Darwin’s and Alfred Russel Wallace’s evolutionary theory and later for the observation of evolution in action. The relevance of processes such as biological invasions and demographic stochasticity for conservation were first recognized through examples from islands. In biogeography, the theory of island biogeography by MacArthur and Wilson is by far the most widely cited and discussed theory. Islands are also hotspots of biodiversity loss, where conservation strategies are being tested that might save some threatened species despite the dramatic degradation of most island ecosystems