Guest Post by Willis Eschenbach
As Anthony Watts highlighted, the recent paper in Nature (paywalled, reported here) on extinctions agreed with the main conclusion that I had established in my post “Where Are The Corpses“. The conclusion was that the “species/area relationship” as currently used doesn’t work to predict extinctions, and thus there is no “Sixth Wave of Extinctions” going on.
This example of an imaginary “wave of extinctions” once again highlights the difficulties of over-credulous scientists as well as the public. The consensus of scientific and public opinion has been that we are in the middle of a mythical “sixth wave” of extinction. In fact, this consensus was much more far-reaching than the claimed consensus regarding climate science … and just as wrong. Sadly, the “Sixth Wave of Extinction” meme is likely to be very hard to kill.
Figure 1. Another alarmist hockeystick. This is the most common graph that comes up on Google Images for “rate of extinction”. I cannot find any attribution for the graph. I do note that we haven’t seen the hundreds of extinctions claimed by whoever made the graph, and that the person who made the graph can’t spell “extinct”. But the graph is hugely popular, replicated on blog after blog.
One web site where this Fig. 1 image is found titles the thread “Bigger Threat Than Global Warming: Mass Species Extinction” … it is good that we have a new measurement standard for threats, because “Terrorism Threat Level Orange” sounds so last decade. And since we already have been informed that global warming is a bigger threat than terrorism, we now have a complete multi-level threat scale — mass extinction > global warming > terrorism. I also like how no animals went extinct from 1700 to 1900. But I digress … here’s the real historical extinction picture since the year 1500, from my post cited above;
Figure 2. Mammal and Bird Extinctions. All causes, all locations. 17 year Gaussian average. The first recorded extinctions resulted from introduced species during the first wave of European exploration of the Western Hemisphere, mostly on Caribbean Islands. The second wave of extinctions is coincident with the spread of various colonial empires (and their concomitant introduced cats, rabbits, diseases, mongooses, rifles, rats, dogs, etc) through the 18th and 19th and into the 20th centuries.
I have pleaded for common sense in this question by asking, where are the corpses of all of these supposedly extinct species? I looked high and low for birds or mammals that had gone extinct through habitat reduction. I found none. I searched the Red List. I searched the CREO list. I started investigating this question of extinctions at the end of 2001, as a result of E. O. Wilson, Stuart Pimm, and other co-authors publishing their extinction claims (pdf) in December 2001 as a rebuttal to Lomborg’s “The Skeptical Environmentalist”.
By March 2002 I had written and privately circulated what eventually (with much interesting research and analysis omitted) became my 2010 WUWT blog post on extinction, “Where Are The Corpses”. By dint of burning gallons of midnight oil (organic CO2-free oil, I might add), it took me three months, while working full-time at a day job, to establish from the actual extinction records that Wilson was wrong. I tried to get the results of my analysis published in 2004 with no success. And fair enough, my submission was not in the best of shape. If I were the editor I might have turned me down. Although the ideas were all there, the problem was I didn’t speak the scientific dialect of Journalese all that well back then. Still don’t, for that matter. But all along I have said that the huge, overblown extinction numbers were a fantasy. And almost a decade later, the latest study in Nature agrees.
There are several lessons that I draw from all of this. I sometimes divide lessons into three piles—the good, the bad, and the interesting. First, the good. Science eventually is self-correcting. The claim that 27,000 species are going extinct every year and the “Sixth Wave of Extinctions” will end up in the trash-bin of alarmist scientific claims.
Next, the bad news. The self-correction is way, way too slow. The claim of extraordinary extinctions was made by E. O. Wilson in 1992. It’s 20 years later, and the process of throwing out the garbage is just begun. C’mon, folks, this the 21st century. We need to become much more skeptical overall. The self-correction process of science needs to start moving faster. We can no longer afford the delays occasioned by the blind acceptance of incorrect theories. Scientists these days are nowhere near suspicious enough. And there’s more bad news.
Once again, we have a “scientific consensus” which is based on heartfelt emotion rather than actual data. I see Wilson’s claim as the source of all of this. In 1992, he said that some 27,000 species were going extinct each year. When I read that, my Urban Legend Alarm started ringing loud enough for Helen Keller to notice. I said “No way that can be right, the number’s way too big” … and it appears I was correct.
Unfortunately, this claim fit right in with the environmentalists reasonable desire to minimize clear-cutting of tropical forests. Confirmation bias raised its ugly head, and as a result the extinction numbers were never examined. Instead, the bogus claim immediately found its way onto bumper stickers and T-shirts and rainforest campaigns.
Now, I grew up in the middle of the forest, with no neighbors for miles, and I love the forest. So don’t get me wrong. The problem was not the environmentalists’ legitimate desire to properly protect or manage the forest.
The problem was the bogus claim of thousands of extinctions, a claim that unfortunately fit too perfectly into the reasonable desire to stop wantonly clear-cutting the rainforest. Here at last was the magic bullet, the way to the public’s consciousness (and wallet). It fit so well that nobody wanted to listen to their own urban legend alarms. Nobody wanted to be the one to say “27,000 extinctions a year since 1992 … that’s half a million species that are supposed to be dead … how come we haven’t seen any of them yet?”. So as in the CO2 debacle, the environmental movement once again, and from the best of motives, threw its not inconsiderably weight behind bogus science.
That’s the good and the bad, now for the interesting part. How does such a consensus persist? Generally, by special pleading. If you can’t argue the pig, you argue the squeal.
For example, one of the main exponents of the species/area consensus on extinctions is Dr. Stuart Pimm. He was one of the authors of the attack on The Skeptical Environmentalist that I mentioned above. He was also courageous enough to comment on this issue on the thread Anthony started that I cited above, and that gets my respect. I like to see a man who is willing to publicly stand up for his ideas.
Dr. Pimm says that his studies have shown that the species area relationship is actually borne out by the evidence. In his comment to that thread, he lays out his explanation in one of my favorite ways, the “thought experiment”, as follows:
Imagine destruction that wipes out 95% of the habitat in an area metaphorically “overnight”. How many species have disappeared “the following morning”? The paper tells you. It is not many, just those wholly restricted to the 95% (and absent from the 5% where they would survive). The important question is …
How many of additional species living lonely lives in their isolated patches (the 5%) would become extinct eventually because their population sizes are too small to be viable? A different species-area curve applies — the one for islands, which are isolated. It is a much larger number of extinctions, of course, and the one used in the studies mentioned above that find such compelling agreement between predicted against observed extinctions.
That sounds right … if his species/area relationship theory is correct. Some species would go extinct immediately. The rest would follow an exponential decay from that time to when they reach their new equilibrium. So we’d see an immediate effect, then a decreasing number of extinctions as the years went by until the final equilibrium was reached. If his theory is correct.
But when I read Dr. Pimm’s actual work, I don’t find the names of actual species that have gone extinct from habitat reduction. I don’t find “compelling agreement between predicted against observed extinctions”. Instead, I find things like this example, from “Timeline Between Deforestation and Bird Extinction in Tropical Forest Fragments” :
Our previous work employs the familiar, empirical relationship between the size of an area, A, and the number of species it contains, S, to predict how many species should eventually be lost when forest area is reduced. We have two cases studies: the Atlantic Forest region of South America (Brooks & Balmford 1996) and the islands of Southeast Asia (Brooks et al. 1997). The global survey of Collar et al. (1994) includes lists of the bird species threatened with extinction in these regions. The predicted numbers of species lost from deforestation closely match these independently compiled totals of threatened species. This match suggests that these threatened species will indeed become extinct in due course and thus that we can predict the eventual species losses.
Note that the “species/area relationship” being applied to extinctions is described as the “familiar, empirical relationship”. This is an indication of the strength of the consensus regarding the claimed relationship.
OK. What’s wrong with the logic in Dr. Pimm’s paragraph?
His logic goes as follows. Having noticed that there have not been any bird extinctions from habitat reduction, he explains this by saying that the birds are “destined for extinction”. His species/area relationship predicts a certain number of extinctions. He finds that according to the Red List, about that same number of birds are “threatened with extinction”. This, he says, shows that his estimates are very reasonable, supporting the idea that the species/area relationship is correct.
There are two problems with that. The first is a problem with the evidence. Even if we assume a fairly long period until the calculated number of species goes extinct, the cutting of the tropical forests has been going on for many decades now. Plus as Dr. Pimm says, some species, perhaps not a lot but certainly some, should have gone extinct immediately. So from those two effects, we should have seen some bird and mammal extinctions by now. But we haven’t seen those predicted extinctions from habitat reduction. This makes his claim very doubtful from the start.
So that’s a problem with the evidence. I go through the actual numbers in “Where Are The Corpses?“. By now, if we really were in the midst of the “Sixth Wave of Extinctions”, someone should be able to point to dozens of bird and mammal species that have gone extinct from habitat reduction even if the extinctions occur very slowly. So the evidence doesn’t support his claim.
(Let me digress a moment and request that people not say “but what about the quagga, it’s extinct”, or “you left that noble bird, the nimble-fingered purse-snatcher, off the list of bird extinctions”. CREO says the quagga is extant under a valid species name, but that’s not the point. I don’t wish to be sidetracked into debating the reality of one or two extinctions. According to Wilson we should have seen dozens and dozens of bird and mammal extinctions by now. Unless you know where those missing dozens and dozens of extinctions are, I don’t want to debate whether I should have included the extinction of the double-breasted seersucker. End of digression.)
Those are problems with the evidence. But what’s wrong with Dr. Pimm’s logic?
The problem with the logic is a bit more subtle. If you go to the Red List, yes, you will find that those birds he mentions are indeed listed as being threatened with extinction. So at first blush, it seems this supports his “species/area relationship” claim.
But why does the Red List say those birds are threatened with extinction?
Well … in most instances, because of loss of habitat … which they say leads to the grave threat of extinction because that is what’s predicted by the species/area relationship.
So Dr. Pimm’s logic is perfectly circular. As long as we accept that there is a mathematical relationship (species/area) between habitat reduction and extinctions, we can show that there is a mathematical relationship between habitat reduction and extinctions. We just declare species that have lost habitat as “Threatened With Extinction”, and presto! We now have the evidence to support the “species/area relationship”.
And since in the 21st century there is hardly a bird or mammal species which has not lost habitat, this allows the placing of more and more species onto the “threatened” lists. It also allows the putative cause called “habitat reduction” to be added to virtually any animal on the Red List … but there’s a huge problem.
The dang creatures just refuse to oblige by going extinct as Drs. Wilson and Pimm have been predicting for lo these many years. They won’t die, the cheeky beggars. Rather impolite of the birds and mammals, I’d say.
Finally, let me use this example to encourage people to use their common sense, to consider the “reasonableness” of the numbers that they encounter. The reality of the 21st century is that we need to run with our “bad number detectors” set to maximum gain. When someone claims that 27,000 species are going extinct every year, think about that number. Does it make sense? Does it seem to be a reasonable size? Extrapolate it out, that’s a quarter million species claimed to be going extinct per decade, a half million species since Wilson made the prediction. Is it reasonable that the world lost a half million species … but nobody can come up with any corpses?
Here is the rude truth about bird and mammal extinctions. Life is incredibly resilient. Once it gets started, it’s a bitch to stop. Almost all of the bird and mammal extinctions were the result of one species (specifically including humans) actively and tenaciously hunting another species to extinction. Most of the time this was an introduced species (specifically including Europeans during the waves of conquest and empire). The main extinction threat to mammals and birds around the planet has never been habitat reduction. It is species-on-species predation in its infinite variety. It was introduced brown tree snakes eating native birds in Guam, and humans hunting the Carolina Parakeets for their feathers to supply the millinery trade in New York.
And these days, of course, it is the “bushmeat” trade that is a huge threat to many African bird and mammal species, including rare and endangered primates. The idea that those species are threatened because of “habitat reduction” or “climate change” is a huge misdirection that obscures the real problems, which are the same problems as always … human predation and introduced species.
My regards to all,
NOTES OF NOTE:
• While I strongly advocate checking to see if numbers are reasonable, “reasonableness” is not in itself something to stand on. It is simply one part of the “smell test”. And the smell test can’t falsify anything. But it certainly can indicate where to take a hard mathematical or observational look to find out why the number seems so far out of range.
• I grew up in the forest. I live in the forest now. When I look out from my back deck I see nothing but redwoods and oaks and bay laurel, with a tiny triangle of ocean glimmering in the distance. I believe in protecting and managing and harvesting and preserving the forests. In addition, biodiversity is always of value to an ecosystem, increasing its stability, adaptability, and longevity. This article is about extinctions, not about whether the forest should be properly protected, harvested, and managed.
• I see that my previous comments have made it into the Wall Street Journal.