The Consequences of the Dissolution of Wallaces's Realms
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The continents of the world have existed separately for eons and evolutionary divergence has proceeded in those separated regions. The interchange of genetic material across the imaginary lines separating those regions(or "realms") has been relatively small. In the last couple of hundred years, human activity has eliminated the geographic barriers between continents with enormous consequences. I'd like to describe what the changes have been, what the consequences are, how we should view it and what we can do about it.
Human activities have increased the rate of exotic species introductions dramatically. For example, between 1961 and 1995 we've added one new species every fourteen weeks in the San Francisco Bay. Exotic species are invading our pristine natural areas such as national parks as well as disturbed habitats. An enormous number of exotic species are being introduced into some areas.
What can we do about this biological revolution? Horticulturists can help by not introducing exotic plants. We need to understand what makes an exotic species invasive and develop methods of control. We can do a cost analysis of what we are losing by having these invasive species in ecosystems which are providing free services for us. We can regulate the importation of exotic species.
We are rapidly creating a new biotic world and we must deal with the negative impacts of our meddling.
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