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Like the Carolina parakeet, which went extinct in 1918? One of the most famous North American extinctions?
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Not a forest bird, according to the Red List, which calls it “wide-ranging”. Your own quote shows it bred and lived “in areas near rivers, in cypress swamps” In any case, the main cause of its extinction was human hunting.
The 27,000 extinctions predicted by Wilson are supposed to be due to reduction in forest habitat. My statement regarded forest birds. If they can live in other habitats, as the Carolina Parakeet could, they would not be driven to extinction by forest habitat reduction.
This poor bird, however, had the unfortunate distinction of being the only brightly colored bird of the parrot family native to the US. It was hunted to extinction for its feathers.
[QUOTE=wevets]
One should, however, note that considering only North America, 68% of extinct fishes are driven to extinction by introduced species. It is possible that intention believed the situation in North America reflects that of the entire world. (Source: Paxton, JR & Eschmeyer, WN (eds.). 1998. The Encyclopedia of Fishes, page 53.)
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As I pointed out before, ascribing extinctions to “habitat reduction” is accepted these days as science. Unfortunately, it has been adopted as a scientific principle without supporting evidence. At this point, we are in a circular argument. Habitat reduction has been accepted without evidence. It is now used to “prove” that it is a real threat by listing it as the cause of a bunch of extinctions. But that is circular, that proves nothing.
A bit of history about extinction and habitat reduction is in order here.
The whole theory is based on the observation that as an area increases, the number of species it contains increases. This is called the “species-area” relationship. We find more species in a state than in a county, for example, and more in a country than in a state. These are related by what is called a “power law”, where the number of species increases as some power (around 0.15 - 0.25) of the increase in the area. This has been extensively verified experimentally.
E. O. Wilson, the noted ant biologist, proposed *without evidence *that this would work in reverse — that if we reduced habitat, species would decrease by going extinct. He said that his calculations showed that 27,000 species per year were going extinct from the cutting down of continental forests.
However, he did not write a scientific paper to advance his theory. He wrote several popular papers that pushed the idea that we are in the midst of a “sixth wave” of extinctions (in addition to the five great extinctions in geological times), with this wave caused by humans. (This, despite the fact that the Red List shows that extinctions peaked around 1900 and have decreased since then.)
This claim was immediately picked up and circulated worldwide, without any investigation of its veracity. It was hailed because it gave a way to mathematically calculate the amount of extinctions from a given reduction in habitat. It was widely used, and heavily advocated, by environmental organizations to lobby against the cutting of the Amazon forests.
But there was no evidence, and no scientific investigation of the claim.
Now, if Wilsons theory were correct, given the amount of continental forest reduction that we’ve seen to date, we should have seen on the order of 23 continental bird and 11 continental mammal extinctions every year from that cause. Just since 1988, when Wilson proposed the thory, we should have seen about 600 continental bird and mammal extinctions from that cause. And since forest habitatat had been shrinking for the last 500 years, we should have seen many more bird and mammal extinctions than that.
In fact, we have seen no forest bird or mammal extinctions. Even if we include the Carolina Parakeet, that gives us one. Where are the other 599 extinctions? We might have missed a few, but not 599 … Wilson’s theory simply doesn’t fit the evidence. Extinctions peaked in 1900, and show no sign of a recent increase.
Why doesn’t Wilson’s proposed inversion of the “species-area” relationship work? Intuitively, it seems like it should work, so why doesn’t it? Possible causes are:
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The species-area relationship is based in part on an increasing number of habitats, not just an increasing area. There are more different kinds of habitats in a state than in a county. Wilson’s inversion only involves changes in area, not in number.
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Species are incredibly hard to kill. They duck and dodge and change habitats and evolve and eat different food to keep from going extinct. Despite centuries of forest reduction, the forest birds and mammals have not gone extinct, simply lived in a smaller area and changed their habits. I asked before how many continental birds and mammals have gone extinct. The answer is, only nine — three mammals and six birds. Despite centuries of hunting and habitat reduction, only nine. Species are amazingly tenacious.
Now, at the moment, through an accident of history, Wilson’s is accepted by mainstream science … as have many other failed theories in the past, from continental drift to helicobacter pylorii. Me, I don’t believe Wilson’s theory, because the evidence doesn’t support it. Whether you believe evidence or theory is up to you, of course.
Intention, you are obviously intelligent and eloquent, but I’m sure your contribution to the discussion would be better if you would check to make sure your beliefs are accurate before you post them as facts.
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Oh, please, let’s avoid personal attacks, I’m on your side. You made an inaccurate claim about whether the Longjaw Cisco was a separate species. I pointed out that DNA analysis said it wasn’t a separate species. You read the paper, and still claimed it was. I pointed out where in the paper it clearly said it was a separate species … and now it doesn’t merit a comment?
I’m not claiming it was just your “belief” that Longjaw Ciscos were a separate species, that would an insult to your obvious intelligence. You found facts that pointed one direction, I found more recent facts that point another direction. That’s how science advances, and how our own understanding improves.
I took the facts I used from the Red List, which does not list the Carolina Parakeet as a forest bird. Maybe that’s a fact, maybe not … but it’s not just my “belief”. In any case, let’s say it is a forest bird, one that was hunted to extinction. This does not make any difference to the falsity of Wilson’s theory … we need to have had hundreds of bird and mammal extinctions in the record to verify Wilson’s theory, and we haven’t seen them.
Finally, I’d like to thank you for your participation in this discussion. Disagreement is how science advances.
w.