Island Biogeography



The biogeography of islands is a fascinating topic that extends to more than just island locations. The ‘island’ part of ‘island biogeography’ can refer to actual islands as well as isolated areas such as mountaintops, valleys, and other secluded spaces of unique biodiversity. These areas, surrounded by unsuitable habitat, often are very high in variety of species of flora and fauna that thrive there.

Island biogeography, or insular biogeography, is the study of places in the world that have different biogeographic and biodiversity levels than the areas that surround them. This field of study was created in the 1960s by two ecologists named Robert MacArthur and E.O. Wilson, who theorized what a newly created island might look like in terms of biodiversity.

Theory of Island Biogeography illustrated in a graph.  Graph: Wikipedia.

Theory of Island Biogeography illustrated in a graph. Graph: Wikipedia.

Specific regions of island biogeography come about in a few ways. They can be areas that split off from a mainland continent many hundreds of thousands of years ago, or areas that limit geographic emigration because of the environment, distance to the next habitable region, and rate of extinction. Insular environments are created by the fact that few species can spread to other locations and other species have a hard time getting to the insular location or surviving once they are there.

Size is also a major factor when it comes to promoting an isolated biogeographical region. A smaller island environment will minimize the amount of species that can survive there, while a large environment will have more species that can live and thrive there. This is also known as the ‘target effect;’ the chances of a species immigrating and finding a larger island ecology zone is greater than the chances of them finding and surviving life on a smaller island area. Size also predicts rate of extinction; smaller isolated zones allow for faster species extinction while on larger isolated areas the opposite is true. After many years the island zone will achieve a balance of biodiversity and remain at a stable level of immigration and extinction.

Factors that influence the creation and longevity of island biogeography include the degree that the zone is isolated, or the distance between the next nearest landform and continental mainland; how long the area has been isolated from other regions around it and how close it is to achieving equilibrium (or how long it has maintained equilibrium); size; climate; baseline ecological makeup; current ecological makeup; location relative to wind and ocean current patterns; the chances of accidental species coming in contact with the area; and, finally, any human activity in the region that might affect the zone directly or indirectly.

Scientific studies have been done in the recent past, and many scientists have studied the fossil records of locations around the world to further the theory of island biogeography. More and more areas around the world are being discovered around the world, and new areas of island biodiversity are being created with the expansion of human settlement across every corner of the globe (for better or for worse).

Research in the Florida Keys involving the repopulation of islands was conducted by E.O. Wilson and colleagues to study the theory of island biogeography. They found that islands closer to the North American mainland repopulated their arthropod species faster than islands further away, which was in line with the original theory. Studies regarding the ecological implications of the island biogeography theory have also been conducted in regions around the world.

There are many implications for the scientific community that stem from studies of island biogeography. Implications for national parks, the future of plant and animal conservation, and the design of wildlife corridors are all affected by the results of studies regarding island biogeography. The study of island biogeography can influence the size of national parks (to improve biodiversity and mitigate the effects of immigration and extinction), affect where wildlife corridors are placed, where, and how big or small they are; and can help researchers pinpoint areas where plants and animals might be in danger of extinction or are simply conforming to their evolutionary and environmental journey.

The study of island biogeography might seem simple in theory, but its overarching implications can be understood and used for ecological conservation throughout the world. The continued study of isolated zones is needed, as is the continued understanding of how the evolutionary past has influenced isolated area of biodiversity today.


Wikipedia. Island Biogeography. Web 27 October 2014.

Island Biogeography. 2014. Web 27 October 2014.

Dobkin, David S., Ehrlich, Paul R., Wheye, Darryl. Island Biogeography. Stanford University. 1988. Web 27 October 2014.

Related Resources

Island Biogeography of the Great Basin:  In the Great Basin, habitat islands are formed though the Basin and Range topography in which north-south trending mountain ranges (some peaks in excess of 10,000 feet) are separated by low and broad desert valleys (as low as 282 feet below sea level, in Death Valley).

How Space and Time Affect Conservation Biology: Time and space are two extremely important concepts that are central to formulating theories and models in biotic conservation.