Insularization10 may have immediate impacts, as I mentioned earlier when we were talking about habitat fragmentation, some species require large tracts of undisturbed habitat for their continued existence. They may be lost almost immediately from small habitat islands. These are short-term insularization effects.
As a result of reduced habitat area, insularization is expected to lead to loss of local species diversity in the long term.
- Barro Colorado Island was formed in 1914 with the flooding of the Panama Canal. Of the 208 birds that bred on the island prior to flooding, 48 have gone extinct.
- At the last glacial maximum, all of the islands on the Sunda shelf - Borneo, Bali, Java, and Sumatra - were part of a much larger southeast Asian landmass. They were probably separated from the Malay Peninsula (and from one another) by 10,000 years ago. Based on the assumption that the species area curve for the present mainland also applied to the islands when they were part of the mainland, we can calculate how many species have been lost from each of the islands (Table 1).
The loss of species as a result of insularization often referred to as ``faunal collapse,'' reflecting the animal bias of the people who have worked on the problem. Nonetheless, this aspect of island biogeography is broadly accepted, and is the basis for many estimates of extinction rates.11 More controversial, and much less certain, is the application of the equilibrium theory of island biogeography to the design of nature reserves.
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