Island Biogeography Theory

¶ … island biogeography theory have affected the principles and practice of conservation design. Changes in equilibrium theory have caused revision in the equilibrium theory of island biogeography pioneered by MacArthur and Wilson (1963, 1967) that shaped local and global conservation designs. Since the 1970s and more particularly the 1980s, scientists have discovered that although the equilibrium theory may be heuristic it has massive holes in both its practicality and authenticity that impair it from being accepted seriously. As a result, principles and practice of conservation design have changed too (Wu, 2008).

The best way to see the difference is by understanding the equilibrium theory of island biogeography posited by MacArthur and Wilson and the results in design that accorded. All of these notions have since been overturned. Drawing on the popular equilibrium theory, MacArthur and Wilson posited that species diversity on an island was primarily and constantly engineered by the twin variables of immigration and extinction.

To that accord, therefore, their theory predicted four results: (1) that diversity on any given island would function according to an equilibrium homeostatic rate of equal immigration to equal extinction; (2) that there would be a proportionate effect of island to mainland distance effecting species' immigration rate, and similarly that the area of the island would impact extinction rate; © that there would be a higher equilibrium rate of greater diversity on the more remote and secluded islands; and that (4) the smaller and less distant islands would evidence a proportionate higher turnover of species (Wu & Vankat,1991).

The equilibrium theory posited that predictions could be reliably built on this specifically since nature was accepted as homogenous, deterministic, and stable influence. Inferentially, therefore, engineers and theorists of conservation design set about constructing their projects on the island biogeography posited by MacArthur and Wilson. Some of the projects that were particularly engineered around these ideas were designs for nature reserves.

In the early 1970s, principles from Mac Arthur and Wilson's were presented and employed by the "World Conservation Strategy" later implemented by the International Union for the Conservation of Nature and Natural Resources in 1980.

Some of the architectural ideas accepted and based upon the equilibrium supposition included the following: (1) That a large reserve was preferable to a smaller one and therefore animal species were housed in large reserves 2)That a single large reserve was preferable to several smaller tracts of land that totaled the same size as the large one (3) That when two or more reserves had to be employed the inter-reserve distance joining them should be as short as possible in order to encourage immigration and discourage extinction thereby leading to diversity (4) That corridors between reserves should be included in design so as to encourage species immigration and that (5) A circular shape was best for design of the reserve since it minimized tendency for the species to disperse within the reserve (Wu & Vankat, 1995).

Within the last few decades, however, it was discovered that whereas the theory on which those designs was built may have been heuristically beneficial, the equilibrium theory itself was scientifically full of holes, groundless, in fact, and therefore, impractical (ibid.). Instead of the notions of equilibrium, steady state, homogeneity, and stability that were thought to exist in nature on a constant level (e.g.

Botkin, 1990), scientists discovered instead that many of our environmental designs and understandings of islands were built on myths and that nature instead was in constant imbalance and flux, patchy and arbitrary (Wu & Loucks, 1995) with stochastic and heterogeneity its prominent characteristics. A new ecological paradigm has emerged called the hierarchical patch dynamics paradigm (HPDP) which now drives design in alternate ways (Wu, 2008). No longer are influences on the protected area (of, for instance, the reserve) considered nor is the heterogeneity for the internal areas controlled and supervised.

There are allowed to be multiple sources for species.