Saturday, September 12, 2015

A Question About Extinction

I was watching an older television show, and, in the course of the story, some statement was made about the "accelerating rate of extinction", which raised a few questions for me. It is a statement we hear made with great regularity, but, as far as I can tell, it is one which lacks much in the way of foundation.

Now, there are a number of issues with this statement, some I have mentioned before, and some new, so please bear with me if you heard some of this before.

First, there is the question of what constitutes a species. In recent times there seems to be a tendency, at least in the circles which define endangered species status, to redefine what were once simply subspecies, or even coloring variations or regionally isolated populations of the same species, as whole new species. And this is important, as have we truly "lost a species" if an otherwise absolutely identical creature exists, differing only in color scheme, tail length or mating call? Even if the two populations cannot interbreed any longer due to isolation from one another, if that is the sole difference, does that mean we have suffered a tragedy if one population or the other disappears?

Second, what about species that "disappear" because they evolved into something else? Are we to fight against evolution in the name of conservation? Often, when a species is undergoing changes due to altered environmental factors, or even because of the emergence of a mutation which makes the descendants more effective in exploiting a niche, some of the first species will linger on, but they are slowly being forced to die out. Is this to be seen as a bad thing? Is nature to be condemned for not retaining "backup copies" of every species that ever was?

Third, how do we know precisely how many species exist, much less go extinct? As far as I can tell, most such figures, such a "we lose 100 species a day" or "a week" or whatever, are largely based upon guesses as to how many species are assumed to exist in unexamined regions,  coupled with equally nebulous guesses as to how many are lost. If you were to ask for a list of which 100 species were lost last Tuesday, no one could provide it, or even a partial list. The number is, as far as I can tell, mere guesswork, and largely unfounded guesswork at that.

Which brings me to the big question, how do we know this number is growing? Our knowledge of historical species is spotty at best, based on quite imperfect records, such as fossils, historical writings, preserved pelts and bones, some few examples preserved in amber, peat and other unusual circumstances, and educated assumptions of the likely evolutionary history of living species. I admit, it is amazing how much we have discovered about the past, but as anyone who works in the field will tell you, the record is very incomplete, and some parts are highly speculative. So, given that, how can we possibly know the rate at which species went extinct in the past? We have a few estimates for large extinction events, and certain very common fossils are conspicuous enough we notice when they disappear, but for more recent times, we really lack any numbers about how many species went extinct and when. So, it seems pretty absurd to argue the rate is increasing, when not only do we not really know the present rate, but we don't know the past either.

None of this is meant to argue that wiping out species without reason is a good thing (and yes, there are good reasons to wipe out species, the spirochete causing syphilis, the worms causing river blindness, and a few others come to mind as species I would not mind seeing vanish), but we should be careful before bemoaning a crisis whose existence we cannot prove. Yes, species are going extinct, but that has been true of every moment since life emerged. Nature is not static, it does not have the mind of a taxonomist or a comic book collector, sealing each species in a plastic bag, or hanging on to a small sample of each new life form. Nature is a struggle, and species constantly arise, change, vanish, die out and otherwise alter themselves. Thus, it makes little sense to fret over the simple fact that species are not static, that life changes. It would be much more beneficial to find out, first, whether or not species are vanishing at some faster rate at all, and then, if that change has any meaningful consequence. Only then can we begin to realistically decide whether we should worry about such things.

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