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Theoretical Issues in Plant Biology

Panel Discussion, continued...

Q:  What are some examples of biodiversity and competition which can be used in the classroom?

A:  Students like studying island biodiversity, for instance, the Hawaiian islands. In a sense, all the species that you find on these islands are foreign. They were all introduced either naturally or by us. The interesting question is what happens when you introduce, for example, the Indian mongoose to control rats and the mongoose is active in daylight, and the rats are active at night so they basically never saw each other? Kind of a silly thing you think that somebody would have figured out. There's no reason from an evolutionary perspective to believe that the Indian mongoose would evolve into an endemic species. What havoc it wrecked on the natural populations, for example, on birds. No more than would have been expected of a weedy species like the California tarweed. It first settled on the Hawaiian Islands and then radiated into the tremendous silver sword, green sword, and a series of plants that are now endemic and have great importance in the Hawaiian Islands. So it's kind of a peculiar dilemma that is kind of fun to explore with your students. Because we're introducing exotic species on islands, suddenly things are different.

Q:  How does the rate of extinction from natural phenomena compare with that happening in the current period?

A1:  If it's only the issue of temperature change and atmospheric change, people always say, well, that happened in the past. And that's true, all these things have happened in the past. It's the rate of change that we just have in all of those issues. Look at the rate and look at the change and go back and see where we are in comparison to where we were, to the rate which is the critical issue.

A2:I'd like to say something and have Bruce respond to it. I think from what he said earlier, that he may have lead people to believe that extinction is to be expected and we shouldn't be exactly concerned about it. I fear that maybe some people might think Bruce would disregard the dire extinction consequences espoused by other members our panel today. It might just be a matter of mere evolutionary biodiversity. But it is this grade, this accelerated grade. And you hear different figures. You hear figures that are anywhere from 100 times normal background, extinction rate to 1000. They say that the figures will probably accelerate. I think the question that we want to look at is, how much depletion in terms of extinct species can any particular ecosystem stand before it cannot rebound. Is that clear? Am I making the point clear? I don't know that any of us have an answer. Maybe it's something we can toss around later.

A3:  Let me start off by responding to your first question in which I gave you the impression that the depletion of biodiversity is not significant, and it's happened before. I will restate what I've said in the initial portion of the presentation. If depletion of biodiversity has occurred before, in some cases we think it occurred fairly rapidly. At least one example, we use the impact of meteorites as having something to do with the Cretaceous/Tertiary boundary that changed in a matter of years, certainly within a century, if you believe the model.

The difference is when I would say, "yes, extinction is a past feature", and when I would say "what we've heard of today is a concern." Because again, we're the first species to be aware of what we do. We have the responsibility as people. Secondly, I think one of the distinct casualties of extinction is going to be the silly little hairless bipeds that started it from the first. And I guarantee you that the ecosystem will be back. It will rebound without us. We will have, I personally think--this is a value judgment--the moral error of having created the extinction and we will also have made the national selection error, I presume, if we carry this off far enough, of the genetic little bits up here. So, yes, extinction has occurred in the past. The extinction process, sometimes occurs very rapidly. This is probably one of the most rapid extinctions ever on the face of the earth, but the earth will rebound. But do we care about ourselves?


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