Guest Post by Willis Eschenbach
In a recent post here on WattsUpWithThat called The Thirteen Worst Graphs In The World, Geoff Chambers explores the graphs in a new book called “10 Billion”, by Stephen Emmott. The book appears to be Emmott’s first entry in the “Future Failed Serial Doomcaster” competition. I thought I’d take a look at one graph, the graph of extinctions. I know a bit about this subject, with both a detailed blog post called “Where Are The Corpses” and a journal article co-authored with Dr. Craig Loehle on the subject. Figure 1 shows Emmott’s graph in all its primordial glory.
Figure 1. Unlucky number 13 of the “13 Worst Graphs” of Stephen Emmott. SOURCE The citation says “13. Adapted from S. Pimm and P. Raven, Biodiversity: Extinction by numbers, Nature, 403 (2000); A. barnosky [sic] et al. Has the Earth’s sixth mass extinction already arrived?, Nature, 471 (2011).
I’ve located non-paywalled copies of the Pimm and Barnosky papers. I’m sure the alert reader can see a few problems with Figure 1 at first glance, including chartsmanship of the highest order. The things that caught my eye were the use of the logarithmic vertical scale; the lack of units on the vertical scale; the short level section followed by the abrupt jump around 53,000 years BC; the huge increase at the end; and oh, yeah, see the little hash marks ” // ” along the bottom time scale to the right of -50,0000?
As is my practice, I digitized this. Took about five minutes, because on a simple uncluttered graph you can use the automated features of the digitizing software. But before I discuss that, let me make some general comments.
Now, you recall I pointed out the hash marks in the time scale in Figure 1? Usually, that just means they’ve left out a chunk of years, it’s a common and legitimate technique used to show two separate time periods on the same graph. But they usually don’t splice the graph lines for the two periods together as he has done.
In addition, in this case the hash marks don’t mean just that. In this case, it also signifies a change in the time scale itself. So on the left side of the hash marks, the graph shows a span of about ten thousand years. On the right side of the hash marks, on the other hand, it shows a span of only about two hundred and fifteen years(1835-2050). Bizarre. The consequences of this are displayed and discussed later.
Next, regarding units, the extinction rates are usually given in units of extinctions per million species per year, or E/MSY. This makes comparisons awkward because we don’t know how many species there are. We can reduce the inexactness somewhat by noting that the Red List shows 207 extinctions of birds and mammals over the last 500 years. And in total, they list 15,565 species of birds and mammals. That gives us a raw rate of about 25 extinctions per million species per year (E/MSY). And that’s roughly the number that they give for the recent part of the data. So it seems that they are using the standard units, E/MSY.
The problem, as always, is in the interpretation of the data. As usual, humans are to blame, and I say that in all seriousness … just not the way the alarmists claim. For example, I’ve shown that the coral atoll damage ascribed to rising sea levels from human CO2 is actually due to human interference with the reef. Humans were the cause, but not from CO2.
And I’ve shown that the damage ascribed to human-caused warming in the Alaskan “climate refugee” village of Shishmaref is actually a combination of poor site selection (it’s on a barrier island), erosion due to poorly designed shoreline reinforcements, and human-habitation-and-road caused permafrost melting. Again humans are the cause … and again, from something other than CO2.
In the case of extinctions, once again humans are indeed the cause … but again, not through the mechanism they claim, that of habitat reduction. Instead, humans have caused widespread extinctions through the introduction of “alien predators” into new areas which had never before seen them. These alien predators were and are a wide variety of species, humans among them. The list includes dogs, cats, rats, rabbits, foxes, mongoose, gray squirrels, brown tree snakes, and a host of other species including funguses and diseases. Heck, in a wonderfully strange case of environmental recursion, it turns out that for a while the lovely Central American frogs were being helped to extinction by the fungus unknowingly spread by the very biologists studying their extinction … introduced predators.
And those introduced predators have wreaked untold damage, including but not limited to both species extinctions and local extirpations of the native species in Australia and the islands around the planet. The changes are not limited to the extinctions because, for example, when you introduce foxes to an Arctic island, the entire ecosystem changes, all the way down to the very plants covering the landscape.
But there’s an oddity in that kind of extinctions, those caused by introduced alien predators. It is reported, perhaps apocryphally, that when Alexander the Great saw the extent of his domain he wept because there were no new worlds left to conquer. And the same is true regarding extinctions from introduced predators. Most of those extinctions occurred in several waves. First there were early extinctions in the Caribbean in the 1500s. Then extinctions rose again during the first wave of expansion and exploration in the 1700s, and then again during the age of empires after 1850. Since peaking at the start of the 20th century, they’ve generally declined. Here’s the data from my earlier post .
Figure 2. Bird and mammal extinctions. Note that the units (extinctions per year) are different from the units in Figure 1 (E/MSY). ORIGINAL CAPTION: Stacked graph of the historical extinction rates for birds (grey) and mammals (black). 17 year Gaussian average of the data from Red List (birds) and CREO (mammals). Note the peak rate of 1.6 bird and mammal extinctions per year, and the most recent rate of 0.2 extinctions per year.
But in 2013, as with Alexander, there are few new worlds left for alien predators to conquer—there’s not much of the planet that hasn’t already seen invasive alien predators of many kinds. There’s no Terra Incognita that hasn’t been visited by the European or other explorers. And as a result, the worst of the extinctions from introduced predators are behind us.
Now, if we leave out the extinctions by introduced predators, then out of the 207 bird and mammal extinctions there are only 9 extinctions in 500 years, three mammals and six birds. This means that other than extinctions from introduced predators the extinction rate is only 1.2 extinctions per MSY … very low.
So with that in mind, here is the underlying data from Emmott’s graph in the normal form, showing both the early and late data.
Figure 3. Emmott’s data from his 13th graph, in the normal form, but still with a logarithmic scale.
Pretty hilarious, huh? When the Emmott data is put into its normal form we see the lunacy of the graph that he has spliced together and present. There is some data from 60,000 to 50,000 BC, then a huge gap in the middle followed by a few more years of data at the end. In order to understand it, let me divide it into the ice age record, and the modern and predicted record, and show each one separately.
Figure 3. Ice age extinctions, from 60,000 BCE to 49,500 BCE. This shows the normal presentation without the logarithmic scale
Now that, I have to call hokey. It has a huge jump between 53000 and 52000 years BCE, and while I imagine that it is supposed to reflect the so-called “Late Quaternary Extinctions” of the megafauna, I’ve never seen it represented like that. Nor do I have any idea why it would jump up and not come back down again … and I can’t find any such jump in the two works he cites, Pimm and Barnosky.
Moving on to the modern era and the future, here’s that chart. Since I don’t know what extinctions he’s talking about, I fear I can’t give the proper background of extinct animals. In Figure 4, you can see that the man is truly barking mad:
Figure 4. Modern and future extinctions, as Emmott would have us believe. Note what happens when we use the normal scale instead of the logarithmic scale.
Here’s the looney part. From 1835 up until the present (2013), the extinction rate is claimed to increase slowly from 16 E/MSY at the start to 28 E/MSY in 2013. Over the next 30 years, to 2043, this slow increase is supposed to continue at the same rate, with the 2043 value estimated at 37 extinctions per million species per year. Then, in seven short years, by 2050 it’s supposed to increase more than a hundred fold, to 4,600 in 2050. Does he really believe this pseudoscience?
First off, there’s no indication that the extinction rate has been rising steadily since 1835 as he claims. Compare his claims in Figure 1, to Figure 2 for what the data actually shows about the historical waxing and waning of extinctions over the years.
More to the point, my goodness, what’s supposed to happen in 2043 to drive extinction rates up by a factor of more than a hundred, two full orders of magnitude, up from 37 extinctions to 4,600 extinctions per MSY? A nuclear winter? A meteor strike? Runaway gene-spliced chimeras? The world wonders …
Finally, some of these numbers are supposed to be “after” Barnosky et al. That paper says:
The maximum observed rates since a thousand years ago (E/MSY ≈ 24 in 1,000-year bins to E/MSY ≈ 693 in 1-year bins) are clearly far above the average fossil rate (about E/MSY ≈ 1.8), and even above those of the widely recognized late-Pleistocene megafaunal diversity crash.
However, recall from above that other than extinctions from introduced species, which will never again reach the high values of the past, the current rate of extinctions is only about 1.2 extinctions per million species years … not different from the fossil extinction rates.
So in summary, Emmott took three different datasets. One was a bogus dataset regarding the middle of the last ice age. The second was a bogus estimate of modern extinction rates. The third was a colossally ridiculous estimate of the future changes in extinction rates. He spliced them all together and voila! The famous extinction hockeystick is born, the 13th unlucky bastard step-child of one Stephen Emmott.
Sometimes, these guys are beyond parody.
w.
Spreadsheet containing the digitized data and graphs is here.
PS—Yes, I know there are many other factors to consider in figuring historical extinction rates, it’s in the journal article. These are rough, raw, “order-of-magnitude” estimates. However, when everything is considered, the modern extinction rates (absent introduced predators) is not statistically any different from the historical rates. In other words …
The claimed “Sixth Wave of Extinctions” is a total fabrication.
Extinction rates are little changed from fossil rates, except for the historical wave of introduced predator extinctions, which are now safely in the past since there are no more empires left for Alexander the Alien Predator to conquer.
PPS—There’s a good discussion of the Emmott graphs over at Donna Laframboise’s excellent blog NoFrakkingConsensus. Geoff Chambers has much more information on Emmott at his blog. And at ClimateResistance there’s a very readable fisking of the individual claims.
PPPS—For an example of the “Sixth Wave of Extinctions” pseudoscience coming from a major environmental NGO, see the WWF … sad.
Klem says:
“The thing is, when I was a kid I used to believe fear-mongering graphs like these, I believed them completely. When you don’t know any better you assume the data is correct and that they did real science, you assume that they are experts and the resulting graphs are accurate”
Yeah I remember getting a book out of the library which showed giant ships towing icebergs from Alaska and Antarctica to supply fresh water to San Francisco and Australia, 3rd world war over dwindling oil and water supplies, glaciers advancing towards New York city again…you get the drift. Wish I still had it, I forget the name of it.
Pimm & Raven 2000 forecasts an acceleration in extinction due to habitat loss from human activities:
http://www.nature.com/nature/journal/v403/n6772/full/403843a0.html
They focus especially on endangered forests, which of course benefit from more atmospheric CO2. One way to save forests both directly (from cutting for firewood) & indirectly (from fertilizing the air with plant food) is to use more fossil fuels.
The graph is truly egregiously bad. I suppose the little bump up c. 53 kya is meant to reflect human occupation of Australia, but don’t know. The graph skips over the biggest Pleistocene & Holocene extinction pulses, those at the end of the last glaciation, as of the megafauna on many continents (although dwarf woolly mammoths survived on Wrangel Island until ~2000 BC), & then again during human expansion onto oceanic islands amid global population increase.
Past human-induced extinction has resulted from introduced species, emphasized by Willis, & by habitat losses Pimm & Raven cite, plus hunting, disease & natural, ie non-human, causes (not that we’re unnatural), & combinations thereof. Hard rationally to blame man-made CO2.
Thanks Willis, but I would not even look at these beyond-parody lies.
Henry Clark says:
July 8, 2013 at 2:01 am
“I once wondered why hardcore alarmists so tend to be dishonest, but then I realized there is a selection effect. A casual can be mistaken out of mere ignorance, but, by the time someone spends enough time on a subject to be heavily involved in publications on it, they usually know better and face the great litmus test of either (1) staying honest and hence becoming a non-PC skeptic, (2) getting quiet, or (3) not minding alarmist dishonesty practically at all and joining it.”
That’s a very good explanation. Can we call it “Schneider’s Razor”?
I occasionally talk to one or the other alarmist and it always feels like falling into an intellectual sinkhole. Schneider’s Razor could be the explanation.
geoffchambers says:
July 8, 2013 at 3:47 am
“Hilary (July 8, 2013 at 1:28 am)
Your comments aren’t off-topic at all. They take the discussion forward from the point that Willis has brought it to with his magnificent demolition job.
There’s no point in correcting a lot of false information unless you go on to ask the questions you raise: “What were they thinking of?” (“They” being Penguin/Vintage Books, but also top publishing firms in Germany, Holland and Italy, the Royal Court Theatre, the European Union, which financed Emmott’s show at the Royal Court, Microsoft, etc).”
You can sell this book to about half of the German audience for books; maybe more. Don’t forget that ALL German parties are Green parties and thrive on catastrophism. The CDU and FDP voters which make up half of the voters don’t really like that their parties have become Green parties but it was tactically necessary to be able to out-green the Greens. The other half, the left-leaning voters, are catastrophists to a man. They don’t care how shoddy the book is; they need confirmation. These people are deeply convinced that we’re going to hell in a handcart. When I point them to all the windmills and solar panels and say, but hey, look how much we do to save the planet, don’t you feel better now? they invariably say, this is not enough, we need to stop driving cars, or something like that.
They’re so depressive it’s funny. I actually like to talk to them.
The only hockey stick produced by climate alarmists that concerns me is their rate of spending. Joanne Nova has the data and graph here: http://joannenova.com.au/2009/07/massive-climate-funding-exposed/
Not quite as impressive as Emmott’s #13, but if she had added in a stick, i.e. the US Gov has been around since 1789 or so, like Mann does to his stick, and compressed the time scale to fit, it would probably look like #13.
George Turner says:
Elements of the urban environment may be so different from the surrounding rural environment that in many cases each city or metropolis may act somewhat like an island, harboring species that are cut off from the rest of their population. For example, a water loving animal released in Phoenix is going to have trouble making it across the desert to reach other cities, and a non-migratory species that isn’t adapted to harsh winters, yet takes shelter in the warm houses in Minneapolis or Toronto, is likewise stuck there.
Eventually they will specialize and speciate, perhaps producing a different range of new species in every city. This may happen much faster than scientific recognition that common, widespread, everyday pests, pets, and globe-trotting hitchhikers have become new and unique species in many cities where they became established. It’s just a question of time, because we’ve already created drastically altered environments filled with new niches, geographically separated from each other.
This comes to mind. Chalk one up to increased diversity!
“There’s a good discussion of the Emmott graphs over at Donna Laframboise’s excellent blog NoFrakkingConsensus. ”
But no panning by biologists, ecologists, warming scientists,….? Boy it must be desperate when the team and the now disgraced Nature essentially gives a pass to total non-science.
Back when the Isthmus of Panama raised up 5my havoc was wreaked on the marsupials and edentates (among mammalia) of South America, so that over a period of a few millennia the extinction rate skyrocketed. Now in lieu of land bridges we have mail order seed catalogs, exotic pet dealers, bilge water from ships sailing the seven seas, the Suez Canal, etc. Weeds came with the seed packages, worms came with potted plants, and Ukranians brought tumbleweeds to America with their grain. North America has become infested with weeds of exotic origin which have enhanced the danger of brush and grass fires, and compete with good grazing plants for introduced domestic animals, which have largely displaced buffalo, which filled in niches vacated by Pleistocene extinctions. Exotic starlings continue to multiply to fill to some extent the niche vacated by passenger pigeons, providing increasing food for peregrine falcons, whose comeback may be responsible for declining grouse populations, which grouse can usually but no always out fly peres down mountains slopes (at speeds somewhat less than 243mph).
Speed boats spread mussels. Pheasants and chukars now compete with local birds, and Burmese pythons eat and are eaten by Florida alligators. Asian snakehead fish have invaded Florida, along with the snowbirds. A few meters of SLR would do Florida good. It will never recover from this invasion of people and predators. And it will take a few centuries, but without DNA database intervention, seed archiving, and ever better zoos, the earth’s species must go the way of its languages: displace or be displaced. The world is changing before our eyes, but most cowboys don’t know that Lewis and Clark never saw a tumbleweed. We’ve only seen the beginning.
On the bright side, we eat delicious fruit from all over the world–bananas don’t compete with oranges, very much. –AGF
izen says:
July 8, 2013 at 3:03 am
First, I didn’t say that extinctions due to introduced predators had “reached an end”. This is why I ask people to QUOTE MY WORDS if you disagree with me. I never said that, izen, so you’re talking to yourself.
What I said was that the great wave of introduced predator extinctions was behind us. And no, I’m not “assuming” that. It’s what the data is telling us.
So yes, there is still damage to be done by introduced species. But there’s no new untouched land mass the size of Australia out there waiting to have a large number of its species wiped out by predators they’ve never seen, as happened with Australia. Those high extinction numbers from introduced predators are in the past.
w.
milodonharlani says:
July 8, 2013 at 8:22 am
Thanks, Great Sloth. You were doing so well until you said
There is no forest-obligate bird or mammal that has ever gone extinct from habitat reduction. If habitat losses could cause extinctions, we’d have seen dozens and dozens of birds and mammals that would have gone extinct from the cutting down of forests all over the planet. It’s estimated that around half of the world’s forest have been cut down … where are the corpses?
We’ve seen none.
Pimm and company believe the “species-area relationship” works to predict extinctions. I have shown that it doesn’t. Toss that claim in the garbage can, and Pimm along with it. He’ll go to his grave believing he’s right, despite the fact that there’s no evidence to support the specie-area relationship regarding extinctions.
w.
izen says:
July 8, 2013 at 3:03 am
It may be less ridiculous than you think.
Most of the megafauna that went extinct during the Holocene after the end of the last ice-age {mammoths, aurochs etc} had survived through several other glacial cycles. The one big difference this time was massively increased hunting and competition for territory from the expanding numbers of a mammal that had recently developed a new form of social cooperation which was highly successful and leading to a population explosion.
————————————–
Woolly mammoths appear to have been a fairly recent development (from the steppe mammoth, ~200 to 150 kya), but even they made it through the much warmer than present Eemian interglacial, although they shared parts of their range with Neanderthal (& probably Denisovan) humans then. As noted, a dwarf version survived until about 2500 to 2000 BC on Wrangel Island.
The varieties of aurochs were more ancient, but the last Eurasian cow did not die until only AD 1627 in Poland.
AB says:
July 8, 2013 at 12:11 am
…
And a bird species in Cambodia, previously unknown but all along right under the local’s noses.
…
One great tradition of the sciences is to ignore the locals. Their categories of animals “aren’t scientific.” So I rather doubt the local noses were really not familiar with the bird, only the specialists. It’s rather like the discovery that the Ceolacanth wasn’t extinct. The ichtyologist that “discovered” it was walking through a local fish market.
izen says:
July 8, 2013 at 3:03 am
izen says:
July 8, 2013 at 3:03 am
Let me recommend to you the Committee on Recently Extinct Organisms (CREO). The CREO has analyzed the record of claimed recent mammal extinctions. They looked at 170 claimed mammal extinctions. Using modern DNA analysis, taxonomic considerations, surveying thoroughness, and other methods and criteria, they have classified them into three groups:
• “Resolved”, meaning extinct, 61 species;
• “Disqualified”, meaning declared not extinct for various reasons, 79 species; and
• “Unresolved”, meaning no decision reached, 30 species.
The following are the reasons for disqualification:
Currently extant under valid species name
Extinct before modern era, or no positive evidence to show extinction took place in modern era
Surveying inadequate
Taxonomy inadequate
The reasons that some are unresolved are:
Insufficient data to make a determination
Not fully named
Surveying inadequate
Taxonomy inadequate
This is the long way around to explaining that the CREO lists the aurochs, Bos primigenius, as not being extinct because it is currently extant under a valid species name, with the following comment:
Meaning that as a species it is no different from our modern cows, Bos taurus, all of which can interbreed. (In passing, I’d say that “Boss Taurus” is a great species name, puts a serious beatdown on our species name … I mean really, “The Smart Ape”?. What kind of brand recognition does that get us? But I digress …)
In any case, that’s the story of the Aurochs as told by CREO. Just sayin’
w.
Willis Eschenbach says:
July 8, 2013 at 10:33 am
There is no forest-obligate bird or mammal that has ever gone extinct from habitat reduction. If habitat losses could cause extinctions, we’d have seen dozens and dozens of birds and mammals that would have gone extinct from the cutting down of forests all over the planet. It’s estimated that around half of the world’s forest have been cut down … where are the corpses?
We’ve seen none.
Pimm and company believe the “species-area relationship” works to predict extinctions. I have shown that it doesn’t. Toss that claim in the garbage can, and Pimm along with it. He’ll go to his grave believing he’s right, despite the fact that there’s no evidence to support the specie-area relationship regarding extinctions.
——————————————-
I’ll stick to a reply just for the birds.
The passenger pigeon is an excellent example of the combined effects of habitat loss & hunting or trapping on a forest-obligate species. Without the double-whammy of the destruction of Eastern forests with market hunting, they would have survived.
The Carolina Parakeet also succumbed to a combo of habitat loss, hunting or capture & possibly disease.
The Florida Dusky Seaside Sparrow was also primarily lost due to drainage of its salt marsh environment, but you might not consider it a forest obligate. It suffered from other issues, too.
The Slender-Billed Grackle of central Mexico may not have been a forest obligate, depending upon how you define forest, but it was killed off by habitat loss.
Bachman’s Warbler & the Imperial Woodpecker are probably extinct, but have not yet been classified as such.
While this paper on the extinction of old growth forest-dwelling owls around the world might be tainted because of the Northern spotted owl controversy, it IMO makes the case for habitat destruction as the sole, primary or contributing cause in some of the cited instances, such as the Bahamian Andros Island “barn” owl.
http://www.fs.fed.us/pnw/publications/gtr343/GTR-343c.pdf
The Anjouan Island Scops Owl & the Indian Forest Spotted Owlet have since been discovered extant. Some others are instances of island endemism, including habitat loss.
You might imagine that owls on Mauritius & Rodrigues would have fallen prey to introduced species, but that appears not to have been the case for the Mauritius Owl, but rather conversion of its habitat to sugarcane & tea plantations, combined with pointless shooting. The demise of the Rodrigues or Leguat’s Owl appears to have resulted from the combo of habitat loss & predation.
Brace’s Emerald hummingbird is another Bahamian extinction associated with forest habitat loss for agriculture. Gould’s Emerald is also extinct, but it’s not know whether it was native to the Bahamas or Jamaica.
In the same part of the world, we now too have the example of the Cuban Ivory-billed Woodpecker (& probably its kin in the SE USA). The end of the Cuban Red Macaw was probably also primarily due to habitat loss, but again combined with hunting & capture. The main cause of the Grand Cayman Island Thrush’s extinction was probably deforestation, with the coup de grace of hurricanes between 1932 & 1944. The Martinique Amazon Parrot was wiped out by clearing for agriculture, but it might not have been a distinct species. If not, it was extirpated rather than rendered extinct. Same goes for the Violet Macaw.
There are other corpses (since I’ve mostly concentrated on North America & the Caribbean), but I would agree with you that the many dire predictions of impending extinctions from forest habitat destruction are not based upon a huge data base of actual & probable extinctions solely from such loss. That does not rule out such impending doom in the absence of some conservation efforts.
Willis Eschenbach says:
July 8, 2013 at 11:38 am
Efforts are underway to recreate an aurochs simulacrum from selective cattle breeding. Others are trying to bring back the tarpan subspecies of horse, in which enterprise my brother is involved.
I think Willis was being unnecessarily kind concerning that graph. For instance, the “period” between the double slashes and about 10,000 years ago should record the loss of about 30 genera with half of them vanishing for all intents and purposes between about 19,000 and 10,000 years ago (as others ahve remarked small, isolated populations of subgenera survived in some regions considerably later in time, e.g. dwarf mammoth of Wrangle Island). That would minimally imply a nearly flat rate from the double slashes to wherever 10,000 BP ought to fall, and then a stair step. However, I can’t really make out any thing remotely like a true scale for that section of graph.
Concerning extinctions, it seems likely that habitat loss at the end of the ice age really was an important element. While it is quite fashionable to attribute the late Pleistocene extinctions to humanity, especially in the Americas, the arguments tend to presume that it is known when, humanity entered the continents, where they entered, and how rapidly the population grew. In fact this all largely unsupported and increasingly we are seeing evidence that the assumption of a “late” entry by humanity is mistaken, with unquestionable evidence for humans in the Americas by 16 – 17 kya, and several investigators pushing for time depths of double that. At the same time the proponents of humanity as the chief cause of extinctions ignore the survival of large fauna in other parts of the world – Africa being a prime example, where, for example, up until the So. African government mistakenly attempted to reduce elephant herds based upon the assumption that they were a chief cause of “desertification,” elephants and humans survived side by side quite adequately for 100s, of thousands of years.
While it is popular to conceive of Pleistocene humans as specialized “big game” hunters, there is precious little archaeological support for that except in periglacial environments. In the New World the perception was largely the result of a demand by sceptical archaeologists that human artifacts be found in association with extinct fauna before they would accept the suggestion that humans might have entered the continents during the Pleistocene. The association of a Folsom point with “extinct” bison, and of a Clovis point with mammoth bones established the big-game-hunter idea in the public’s and even professional’s consciousness.
There are two other principle hypotheses for the late Pleistocene wave of extinctions. One is “new” diseases. As the corridors opened between the new and old worlds enabling land passages by wild populations, it became possible for naive populations to be abruptly exposed to pathogens for which no existing immunity was present. Since the land bridge is a two-way street it isn’t unlikely that “naive” populations lived on both sides Beringia and waves of extinctions or at least extreme population reductions on both sides are to be expected.
The other suggestion is that habitat changes at the end of the LGA, in combination with the abrupt, powerful and temporary reversal during the Younger Dryas, climate changes lead to situations where suitable habitats for large fauna became small, discontinuous patches without suitable travel corridors connecting them. That would lead to genetically isolated, stressed populations, with reduced available ranges. Depending on luck, or bad liuck, and the rates at which plant communities can expand, this by itself could result in isolated populations with inadequate genetic diversity to survive. That would in turn cause stress among the dependent predator populations (recall the well-known arctic hare/fox chart) leading to population loss and extinctions among the larger predators as well. If your body size is determined by prey size, and the prey shrinks, well either you shrink to meet available prey size (wolves for instance) or you vanish from the world’s stage – Smilodon and the short-faced bear.
Probably a mix of agents is the real cause of these extinctions, and human predation effects is unlikely to be more important than others. In fact, as seen in the Mesolithic in Europe, the diminishing availability of large game would simply have triggered an increasing reliance on smaller game, plant foods, and marine resources. That means that human effects on shrinking big game populations would have steadily diminished as the large mammal populations shrank. Instead of stupidly hunting down and eating the last mammoth, they very likely were roasting jackrabbits and tubers when the last short-faced bear killed an ate the last mammoth calf, while it’s mother died of a disease carried by the American Lion or moose who entered the continent over the Beringian land bridge.
Interestingly, Wikipedia, not my favorite source, does discuss “problems” with the overkill hypothesis, and notes while not observing, that many of the American survivors are descended from recent immigrants from Asia. The only important exception is the bison. Bison survived, musk ox survived, reindeer survived (caribou east of Siberia), but native ungulates by and large didn’t, nor did the predators that depended on them.
Duster says:
July 8, 2013 at 12:40 pm
The graph is execrable as science, so bad indeed that it probably is counter-productive as advocacy. Or maybe I’m hoping too much.
You’re right that the Pleistocene-Holocene transition extinctions were often from a mix of causes, & not just of megafauna. Species which had survived prior such glacial-interglacial transitions, such as those mentioned above & the woolly rhino, fell victim to the combos, including human predation (with secondary effects), habitat alteration & diseases borne by our dogs & us.
In some cases, however, this process took thousands of years instead of the apparently rapid demise of so many species then. In addition to those already cited, the “Irish elk” survived until at least 7700 years ago.
Thanks Willis for yet another educational exposition.
To put their ridiculous theory into perspective, perhaps a complementary plot showing rate of species-discovery can be superimposed on your rate of extinction graph.
Willis the thing that makes your posts great is, in addition to creativity, knowledge and language, is the excellent educators you draw in.
milodonharlani says:
July 8, 2013 at 11:57 am
His rundown on the extinction of birds in the Western Hemisphere is an absolute gem of prose, knowledge and al delightful education.
Duster says:
July 8, 2013 at 12:40 pm
A superb essay on the debate about the causes of Pleistocene – Holocene extinctions of large mammals and their predators, criticizing the almost unmitigated blame of early humans as the chief cause.
Wow this has been a cornucopia of stuff about which I had little knowledge. Indeed, I’ve been hitherto turned off of ecological articles because this area of knowledge is flooded with agenda driven non-science. To me, professional ecology’s become a platform heor largely anti-human
eugenics rants. If the above three people were to write a book on ecology, I would buy it and read it with pleasure. There are a few other posters on this thread that also contributed to my education on the subject. Honorable mention:
agfosterjr says:
July 8, 2013 at 10:19 am
I’ve been thinking that collection of the especially educational comments on a post would make for a good essay on selected topics that would be a true contribution to eclectic knowledge junkies, of which there is a concentration in the WUWT community. I think having the controversies as a central theme of the essays would be an innovation in the genre. Anthony, you have created a thing of great beauty.
Willis, I was just struck with a thought that might lead to an interesting bit of research regarding the Pleistocene & Holocene extinction pulses and where bodies are buried so that we can’t find them all.
If you go back to the low sea levels during the peaks of the glaciation events and calculate the difference in the number of islands and island area, and them come up with some proxy for how many unique species could’ve arisen on the islands during the relatively brief times they were exposed (which is going to be necessarily highly speculative), then you’d have a rough number for how many species went extinct simply to their island’s being submerged by completely natural causes.
Needless to say, evidence of these extinctions won’t be found in a very accessible record because not many paleontologists go scuba diving and chip away underneath meters of accumulated corals to look for a mammal’s femur or a flightless bird’s hip bone.
But the simple inference that the fairly recent past must contain these massive and undocumented extinction events would be another counterweight to the hockey-stick extinction graphs.
Let us all hope Willis’ eagle does not go extinct. It’s probably smart enough to dodge the birdchoppers which are driving the red tailed hawk to local extinction in California. Not to mention the devastating effect on the whooping crane and the California condor.
Re passenger pigeons, David Quammen repeats the story in “Song of the Dodo”: they bred on the ground in flocks of billions that through sheer numbers were impervious to predation. Once their numbers were reduced to the point that predation DID make a dent, they were doomed. Accordingly, any extinction blame must consider primarily those factors which reduced its population to vulnerable numbers–after which their extinction was automatic.
As for Pleistocene extinctions, this has been dragged through the mud many times, e.g. here:
http://wattsupwiththat.com/2012/06/19/the-intriguing-problem-of-the-younger-dryaswhat-does-it-mean-and-what-caused-it/
While the appearance of humans seems to be synchronous with extinctions in Australia, New Zealand, and just about everywhere, it is in particular Clovis spear heads that are found in context of mammoth kills, and it is apparently Clovis technology that did them in. Clovis culture disappeared with the megafauna–their technology was specialized to hunt big game. –AGF
milodonharlani says:
July 8, 2013 at 11:57 am
First, thanks for the reply and all the info on the birds.
My claim was a bit narrower. Here is the proof:
That is a search of the Red List database with the following conditions: extinct birds and mammals whose habitat is forests. Note that despite the ~50% reduction in global forests, there are no forest-obligate mammals or birds that have gone extinct from any cause except a mouse in Galapagos Island gone extinct from the usual cause … introduce predators.
And while it is easy to claim that habitat loss was a “contributing factor”, standing on a piece of paper is a “contributing factor” to my height … so I fear the claim is meaningless. If it were a significant factor, surely we’d have seen extinctions from that cause alone.
But we’ve seen none.
Look, except for man and domesticated animals, just about every bird and mammal on this planet has seen habitat loss … so yes, habitat loss is associated with extinctions. It’s also associated with non-extinctions. It’s also associated with changes in habitat. Almost any animal behavior you name can be associated with habitat loss, because virtually every animal has lost habitat … so what?
w.
DirkH says:
July 8, 2013 at 8:31 am
“That’s a very good explanation. Can we call it “Schneider’s Razor”?
I occasionally talk to one or the other alarmist and it always feels like falling into an intellectual sinkhole. Schneider’s Razor could be the explanation.”
Thanks. Just out of curiosity, while I see an analogy to Occam’s Razor in name style for “Schneider’s Razor,” who is Schneider in this context?