I'd happily invite Mr. T out to my neck of the woods to see the woodland floor carpeted in garlic mustard and nothing else. Or, wetlands full of purple loosestrife, and nothing else. I think he has a clear conflict of interest.

I highly recommend reading his book:
Invasion Biology: Critique of a Pseudoscience
By David Theodoropoulos. Published by Avvar Books, Blythe, California.
ISBN 0-9708504-1-7

http://dtheo.org/InvasionBiology.htm

I have not read the entire book but based on excerpts it appears to be what it claims to critique. His comparison of invasion biologists to Nazis is reminiscent of Godwin's Law. The fact that the author's business is potentially affected by laws restricting the import/export of plants and seeds should not be lost on anyone.

I doubt very much that he is able to explain how the introduction new species to Hawaii or New Zealand has been able to "increase biological diversity, benefit ecosystems, prevent extinctions, and act as an important force for healing the planet."

Some dismiss his ideas without reading the book, but he brings forth some very cogent arguments that challenge the current myopia about organisms and the history of life on this planet.

The introduction of new species HAS increased the biological diversity of of Hawai'i, and New Zealand, just as it has everywhere. It is likely the only benefical action of our species (H.sapiens).

If you think this book is just some polemic, then please take a little time to brush up on biogeography and evolutionary history; the movement of species around this planet is natural, inevitable, and unstoppable. Get used to it.

Introducing species to tropical islands increases species richness, not diversity. Globally it has resulted in a net loss of biodiversity due to extinction of endemic flora and fauna. The rate of species introductions is currently much higher than would occur naturally and has altered ecosystems around the world. Think about the changes that have occurred in northeastern forests as a direct result of the introduction of chestnut blight, emerald ash borer, dutch elm disease, gypsy moth, and butternut canker. Yes, there are still forests here but they are fundamentally different than they were 150 years ago. Many of the trees affected by these organisms are (or at least were) important economically.

How does increasing species richness not increase diversity? If biodiversity is the "totality of genes, species, and ecosystems of a region", then the introduction of species would in fact increase biodiversity. The introduction of species is not the primary cause of extinction, almost all recent extinction is due to habitat loss directly associated with human altering of the landscape for agriculture & development. The rate of the movement of species arount this planet is very dynamic, and rapid movement of species is nothing new.

You are correct, in that ecosystems have been altered. The few remnants of old forests in the northeast may not look the same as 150 years ago, and I'm willing to bet that they will not look the same in another 150 years. Although we may find this disturbing, change is the only constant in nature. That land has been home to dinosaurs, ice sheets, mastodons, humans, and billions of other organisms over very long periods of time. It will surely change again over and over, whether we are here to introduce species or not. I believe that our movement of species around the planet is extremely beneficial. It actually helps to stop extinctions by giving evolutionary lineages new opportunities to continue, and can give rise to speciation.

Species richness refers to the total number of species within a given area. Species diversity includes richness but also takes into account evenness, or the relative abundance of species. You can add a few species to a community and that will, by definition, always increase richness. However if those new species become dominant than the evenness will decrease and along with it the diversity.

I don't know any biologists who would argue that the introduction of species is the primary cause of extinction. There may be laymen environmentalists who have made such a claim but they are not likely scientists. Any ecologist knows that habitat loss is the greatest contributing factor to species extinction. However, there are certainly species that have gone extinct as a direct result of human introductions of new species.

I agree with you that the northeast forests will not look the same in 150 years but only because they are still recovering from past land use. It is estimated that it will take 150-200 years for the understory flora to reestablish. Prior to 150 years ago the forest community composition would have been relatively stable for thousands of years. The last glaciation was at least 10,000 years prior.

The issue where we seem to disagree is whether a constant, high level of human disturbance is a bad thing. I would argue that in the short term we are putting considerable pressure on natural ecosystems and they would be better off without such a degree of disturbance and movement of genes. I would rather visit a place and see the endemic flora and fauna than a bunch of introduced species from another place. A homogenized global environment doesn't seem like a terribly exciting place, and the prospect of new species evolving over thousands or tens of thousands of years doesn't mean much to me in this lifetime.

Then the loss of biodiversity is dependent on a particular species becoming dominant? I'm not sure that any species(except ours), could completely dominate an ecosystem and I am pretty sure that any monoculture would soon be kept in check by some biotic factor. Any species that colonizes a new area will fill some niche that was already present, and then may persist,radiate, or perish. The idea of homogenization is also pure fiction, the number of factors that determine favorable conditions for organisms are too varied to allow this.

There is no difference between wind or wave, bird or bat, monkey or man in the dispersal of organisms around this planet. Endemism is just an accident of geology and evolutionary histroy,all organisms are native to earth, thats good enough for me.

Biodiversity is influenced by a number of factors. What I am referring to is the concept of diversity as it is used in ecology, which takes into account both species richness and species evenness.

Say you have species A, B, and C, and in one community there are the following numbers of each species:

A - 3
B - 3
C - 3

and in another community there are the following

A - 10
B - 2
C - 1

Both the first and second communities both have a species richness of 3, but the first has a higher evenness than the second community. Therefore the first community would have a higher diversity index than the seco="subject" value="RE: David I. Theodoropoulos" size=40>

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