5 - Biology

05 Biology

Island Biogeography Model

Since the 1960s, scientists have been studying the composition and stability of island communities.

Specifically, they have been interested in what it takes to maintain life in these isolated areas.

As a result, they developed the island biogeography model, a model that not only provides information on island populations, but also provides insights into conservation.

The island biogeography model theorizes that the number of different species on an island will maintain equilibrium, or state of balance, amid the fluid changes of immigration and extinction.

In other words, the number of species on an island remains constant. In an experiment in the US state of Florida, islands of mangrove trees were found to house many different species of arthropods.

Scientists documented the numbers and types of species.

They then sprayed insect poison over the islands, destroying all of the arthropods there.

They observe the islands over the next year, as species of arthropods from the area surrounding the mangrove islands moved onto the island and repopulated it.

Within a year, the number of species of arthropods was almost identical to what it had been before spring the poison.

However, the scientists soon discovered that the individual species were not identical to the ones that had been there before.

So, while the number of species was the same, the diversity of species was quite different.

This study proves that although the species number remains constant, the types of species do not.

The island biogeography model can also apply in places that are not technically islands.

In fact, the islands used in this research were man-made, isolated areas that had been created to meet an ever-increasing demand for land and natural resources.

These islands form when humans clear out vast amounts of vegetation for arable land and living space.

Their actions cut off small areas of land and forest from larger communities, such as when loggers separate a small parcel of forest area from the larger forest.

Hence, these isolated pockets become “islands,” or areas separated from their larger communities.

By reducing areas of land and islands, humans have a significant impact on wildlife.

The island biogeography model states that the larger the island, the higher the rate of extinction.

This is due in part to a larger number of species coming to the island to colonize it.

As new species immigrate, there begins a competition for resources on the island.

Since there is a fixed amount of resources on any given island, some species will not survive in the struggle.

On a smaller island, the rate of extinction would be lower, and so would the corresponding immigration of new species.

The more isolated these small islands are, the fewer species they are able to sustain. Certain species of birds and animals may only be found on these islands.

If they lose the competition for resources, they will be gone forever.

For example, the Bulger Botanical Garden in Indonesia was created fifty years ago, leaving an isolated woodland area where lush forest had once been.

Twenty of the sixty-two original species of exotic birds have disappeared completely, and four species are severely endangered.

The model scientists developed has provided beneficial information regarding the conservation of these areas that are threatened by man’s need for resources.

While the demand for land and natural resources will continue, many feel that with planning and a concerted effort, life in these precious island ecosystems can be preserved to some degree.

One solution suggests that a natural corridor be sustained between the isolated communities.

For example, scientists in the Netherlands are looking at the possibility of leaving paths of trees and shrubs between these islands.

They feel it will aid in maintaining the diversity of species there. The island biogeography model has inspired biologists to begin researching conservation methods.

Such methods include the establishment of nature reserves and programs to help plan the use of land in a way that would protect the natural habitat as much as possible.

It is a harsh reality that much of the life on these islands cannot be sustained. Some species will inevitably become extinct.

The island biogeography model first started as a way to explain life in the communities of these isolated ecosystems, but is developed into a catalyst that has sparked heavier conservation efforts on behalf of these endangered habitats.

The model has served as a tool that has opened the eyes of many who hope to conserve as much tropical force life as possible.