On Wed, Mar 12, 2014 at 10:29 AM, John Clark <[email protected]> wrote:
> On Tue, Mar 11, 2014 at 11:39 AM, Chris de Morsella <[email protected] > > wrote: > >> >> >> *On Behalf Of *LizR >> >> >> >>> >> I must admit I've heard the extinction rate is way higher than usual >>> - asteroid / methane burp high. (Although if it's us or them, as I said, >>> that's a different story...) >>> >> >> > >Liz - it is not hearsay [...] There is substantial, incontrovertible >> evidence that the extinction rate has literally spiked through the roof. >> > That's not just hearsay it's idiotic. 66 million years ago 2/3 of all > species, not individual animals but entire species, became extinct quite > literally overnight, and 252 million years ago it was even worse, the > extinction rate was 90%. What we're experiencing now is not even a burp. > You fail to understand the distinction between the extinction RATE--percentage of species going extinct PER UNIT TIME--and the actual percentage of species that have gone extinct in total (akin to rate of travel in a car, i.e. speed, vs. total distance traveled). "90%" is not a rate at all, it's a total. The argument is that the rate has gone way up from the "background extinction rate" in recent history, and if the rate REMAINS this high for another century or two, then the total percentage of species that go extinct will reach mass-extinction levels, even though it hasn't yet. Apparently there is some controversy about the current rate, see discussion of an optimistic paper by Costello et al. at http://www.sciencedaily.com/releases/2013/01/130124150806.htm along with the response from some other scientists at http://www.soc.hawaii.edu/mora/Publications/Mora%20036.pdf ...the response notes that the Costello et al. paper presents an estimate (0.001%-0.1% per year) that's very low compared with nearly all previous estimates, and that a previous paper by one of the coauthors of the optimistic paper, Nigel Stork, had compiled a number of estimates which together gave an average of 0.72% per year, and that "Removing all rates derived from species-area relationships, which are currently debated [(12), but see (14)], still yields a mean extinction rate of ~0.22% or ~11,000 species a year if there are 5 million species." Fig. 1 gives some curves showing the TOTAL FRACTION of species that will have gone extinct in the next few centuries if the rates remain at either 0.72% per year (solid red curve) or 0.22% per year (dotted red curve), you can see that about half of all species would go extinct by 2100 if the rate was 0.72% per year, and about half would go extinct by 2300 if the rate was 0.22% per year. Either one would be a near-instantaneous mass extinction on geological timescales. Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
