Islands are, and always have been, special places. They are especially so for scientists. Islands are isolated and are essentially a living laboratory of evolution. Islands harbor the greatest number of endemic species. The relative isolation of many islands has allowed populations to evolve in the absence of competitors and predators, leading to the evolution of unique species that can differ dramatically from their mainland ancestors. The bad side of island life is that they are places of concentrated extinction. Of 724 known animal extinctions in the last 400 years, about half were island dwellers. Furthermore, the proportion of endemics on islands is positively correlated with this intrinsic vulnerability.
Island species are especially vulnerable to extinction because they have a small geographic range. They are limited to the island or a particular part of the island, and they usually have low population numbers. These factors make them more likely to become extinct as a result of natural factors such as disease, fire, and normal population fluctuations.
If the population is small to begin with, a natural occurrence may occasionally kill enough individuals so there is no longer a viable population of that species. This dynamic is exacerbated when introduced species such as humans, their domesticated animals, pests, and diseases arrive on the island. Native species that have evolved without contact with these new organisms are often unable to compete or defend themselves. Habitat destruction, direct hunting, competition for food, and other factors put intense pressure on island species.
Island biogeography is essentially the study of the distribution and dynamics of insular species. It provides a theoretical and operational foundation for the design of research and management plans for wildlife in Southeast Alaska. Such plans in this highly insular region still have not tuned in to the special attributes of island life. To date, the vast Alexander Archipelago has played a limited role in the evolutionary, ecological, and conservation biology literature, although this system is one of the largest temperate archipelagos worldwide with 7 of the 15 largest US islands. The region could become a model system for testing fundamental hypotheses related to environmental change.