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Biogeography Island Biogeography has been of great interest for geographers. The theory is closely connected with the theory of evolution developed by Darwin. Oceanic islands are isolated areas. They are limited in territory to examine the processes which are too complex to implement them in the mainland areas.
Island Biogeography attempts to identify the factors which influence the diversity of species of a particular community. Islands are unique in their nature. They are isolated areas. The evolutionary processes taken place on islands are more indicative. There is no gene flows to dilute the effects of selection and mutation 1. Scientists have been puzzled by a question of why some islands have more species than others.
In 1967, Edward O. Wilson of Harvard University and Robert H. MacArthur of Princeton University collaborated to develop a theory explaining the uneven distribution of species on different islands 2. In 1967, Edward O.
Wilson of Harvard University and Robert H. MacArthur of Princeton University developed a theory explaining the uneven distribution of species on different islands. In The Theory of Island Biogeography, they theorized that the number of species on an island depends on a balance or equilibrium between the rate of extinction on the island (based on genetics, population sizes and ecology) and the rate of species immigration or colonization to the island. All else being the same, islands closer to the mainland tend to have greater species diversity than islands further from the mainland, and islands with larger habitat areas tend to have greater species diversity than smaller islands. Their theory is supported by considerable research and data and has become an important foundation of modern conservation biology and ecology. Wilson and Macarthur have invented the theory of equilibrium of species on the island.
According to them a number of species on the island remain constant, in equilibrium. This equilibrium occurs because though the species would become locally extinct from time to time; the actual number of species remains stable because new species would come from the mainland by immigration. The authors of the theory did not include the evolution factor because according to them an island population was stabilizing within the period which is short for new species to evolve. The real number of species would depend upon the area of the island and a distance from a mainland.
They created the dependence between the size of an island and a number of species. A number of species depends upon the size of an island, the smaller island is, the fewer individuals of each species present at the island. This occurs due to the fact that on the smaller island the species are easier exposed to the diseases, disasters and other factors causing the extinction of the species. If there are two different sized islands are situated on the same distance from the mainland, the number of individuals of the species on the bigger islands would be more than that of a smaller island. The equilibrium will occur when extinction would be equal to immigration.
A number of individuals inhabiting the island are in inverse proportion to a distance from the mainland. So, these two relationships, the size of an island and the distance from the mainland result the population of an island. If all the life forms are eliminated on the island, say as a result of a natural cataclysm, it would be inhabited very quickly and after its population reaches the equilibrium the growth of the island population will stop. The Theory of Island Biogeography is based on the natural processes and hardly considers the human impact on the ecosystems. As a result of human action, island birds have been 40 -times more likely to become extinct within the last 400 years than continental birds, while altogether about 80 % of documented animal species extinctions in this period have been of island species 3. The human impact on the nature is directly connected with the technological progress.
The technological progress brings the benefits and hazards to the society. The Chernobyl catastrophe in Ukraine is a vivid example on what kind of hazard the technological progress may bring to the ecosystem. The consequences of Chernobyl are to be evaluated in the future, but now it is clear that they are huge. Nearly 70 years ago, a Soviet geochemist, reflecting on his world, made a startling observation: Through technology and sheer numbers, he wrote, people were becoming a geological force, shaping the planet's future just as rivers and earthquakes had shaped its past 4.
The human pressure on the nature today is greater than before. Intensive agriculture combined with the pesticides utilizing pollutes the nature which causes the irreversible changes in the ecosystems. The island ecosystems are self balanced systems and that is why they are especially vulnerable to outer interference. Thus, all Pacific Island Countries and territories (PICTs) suffer from the over-exploitation of coastal and marine resources and ecosystems, none more so than the low-lying atolls and smaller high islands where entire populations rely for their livelihoods on goods and services provided by coastal habitats and resources.
Coastal resources of higher islands such as PNG and Solomon Islands share the same condition, but further compounded by the negative impacts of upstream activities such as poor agricultural and logging practices and indiscriminate land clearing for settlements, infrastructure and other economic activities 5. The losses of nature caused by humans in prehistoric times exceed those of the last 400 years. The most of the losses occurred with birds. The scale of environmental degradation on certain Pacific islands has been shown to have been so great as to have lead to complete cultural collapse and even human abandonment of the island 6.
There are several causes of the island species extinctions. Major of them are the predatory by humans, spread of diseases and habitat loss. Habitat loss in its turn is caused by the technological development of the society alongside with the insufficient environment protection. Islands being the isolated ecosystems are especially vulnerable to the ecological mis balance. Islands species continue to be lost. Though the situation is alarming it is not critical.
The island species can be protected and are being protected. All the conservation measures like habitat protection, pest and predator control as well as hunting control are easy to implement on the isolated islands. It is easier to observe and regulate the ecological balance of the island. The pollution is controllable at the isolated area. The species may be re-insulated by transferring them to other islands with more ecologically friendly environment. All these measures require urgent human actions...
It is time for humanity to pay its debts back to the Nature. Bibliography The Theory of Island Biogeography, available at web G. Radcliffe, Introduction to the Theory of Island Biogeography, April 4, 2005, available at web Rob Whittaker, Island Biogeography: Ecology, Evolution and Conservation, available at web Andrew C. Revkin, Human Impact on the Earth How Do We Soften It?
National Geographic News, available at web retrieved 11. 04. 2005 Biodiversity in the Pacific Islands, available at web Citation The Theory of Island Biogeography G. Radcliffe Rob Whittaker Andrew C. Revkin Biodiversity in the Pacific Islands Rob Whittaker
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Research essay sample on Technological Progress Species Diversity
