Sunday, July 26, 2015

A mammoth "oops" moment at WUWT

Sou | 7:23 PM One comment so far. Add a comment
In another rather silly article at WUWT, Eric "eugenics" Worrall (archived here) misrepresents a paper just published in Science Express. Thing is that Eric agrees with at least some of what the paper says, so in order to claim that "scientists don't know nuffin'", he makes out the authors say something different.

The paper was by a team of scientists led by Professor Alan Cooper from the Australian Centre for Ancient DNA at the University of Adelaide. It was a study of megafauna, using ancient DNA, radiocarbon dating and geological records. What the researchers found was that it wasn't so much cooling that was behind the extinction or reduced populations of large animals, it was periods of rapid warming. After humans populated more of the world, their hunting, combined with rapid warming, were most likely the main contributing factors to the extinction of these large animal species (such as mammoths).

Model at the Royal BC Museum in Victoria (Canada). Source: Wikipedia

Eric chose to misrepresent the paper. He wrote:
Ship of Fools Leader: Humans didn’t kill the Mammoths – climate did
His allusion to "ship of fools" was because Professor Chris Turney was a co-author of the paper. Eric writing that it wasn't humans, is contradicted by both the paper and the press release. I'll give an example from the press release, since Eric used the excuse that the paper was paywalled. (This raises the question of why he'd write about a paper he didn't bother reading.) This is from the press release at ScienceDaily.com:
"It is important to recognize that man still played an important role in the disappearance of the major mega fauna species," said fellow author Professor Chris Turney from the University of New South Wales.

"The abrupt warming of the climate caused massive changes to the environment that set the extinction events in motion, but the rise of humans applied the coup de grace to a population that was already under stress."

A grudging admission from Eric Worrall

Despite his wrong headline, Eric grudgingly admitted the scientists did blame humans for some extinctions, and wrote:
Turney’s abstract grudgingly acknowledges the impact of humans on megafauna. But I suspect the human influence was probably far more important than the climate influence. Otherwise, mammoths would have survived the comparatively feeble warmth of the Holocene, just as they survived much warmer past interglacials, over their long existence.

The demise of megafauna

There's a press release at ScienceDaily.com. So even though Eric didn't read the paper itself, he could have read about it. Then he would have discovered that there's more to the paper than the extent of the contribution of humans. For example:
  • Although many people previously thought that it was rapid cooling that contributed to the demise of large animal species, this research points to rapid warming playing a key role in the past.
  • Abrupt warming is shown to be a factor prior to the emergence of humans.
  • Humans exacerbated the problem, and hunting and habitat destruction by humans has also played a big role.

More from ScienceDaily.com (my emphasis):
Published today in Science, the researchers say by contrast, extreme cold periods, such as the last glacial maximum, do not appear to correspond with these extinctions.

"This abrupt warming had a profound impact on climate that caused marked shifts in global rainfall and vegetation patterns," said University of Adelaide lead author and Director of the Australian Centre for Ancient DNA, Professor Alan Cooper.

"Even without the presence of humans we saw mass extinctions. When you add the modern addition of human pressures and fragmenting of the environment to the rapid changes brought by global warming, it raises serious concerns about the future of our environment."

The researchers came to their conclusions after detecting a pattern, 10 years ago, in ancient DNA studies suggesting the rapid disappearance of large species. At first the researchers thought these were related to intense cold snaps.

However, as more fossil-DNA became available from museum specimen collections and through improvements in carbon dating and temperature records that showed better resolution through time, they were surprised to find the opposite. It became increasingly clear that rapid warming, not sudden cold snaps, was the cause of the extinctions during the last glacial maximum.

The research helps explain further the sudden disappearance of mammoths and giant sloths that became extinct around 11,000 years ago at the end of the last ice age.

"It is important to recognize that man still played an important role in the disappearance of the major mega fauna species," said fellow author Professor Chris Turney from the University of New South Wales.

"The abrupt warming of the climate caused massive changes to the environment that set the extinction events in motion, but the rise of humans applied the coup de grace to a population that was already under stress."

In addition to the finding, the new statistical methods used to interrogate the datasets (led by Adelaide co-author Professor Corey Bradshaw) and the new data itself has created an extraordinarily precise record of climate change and species movement over the Pleistocene.

This new dataset will allow future researchers a better understanding of this important period than has ever been possible before.

The paper provides more detail. For example, this excerpt from the concluding paragraph is a good summary of some of the main points (my paras and emphasis).
Our results lend strong empirical support to the hypothesis that environmental changes associated with rapid climatic shifts were important factors in the extinction of many megafaunal lineages. Indeed, the rapid replacement of local genetic populations by congeners or conspecifics (e.g., cave bears, bison, mammoth) revealed by ancient DNA suggests that broader-scale metapopulation structures or processes (e.g., long-distance dispersal, refugia and rescue effects across spatially distributed subpopulations) were involved in maintaining ecosystem stability during the repeated phases of sudden climate change in the Pleistocene Holarctic. If so, human presence could have had a major and negative impact on megafaunal metapopulations by interrupting subpopulation connectivity, especially by concentrating on regular pathways between resource-rich zones (1), potentially leaving minimal signs of direct hunting.

By interrupting metapopulation processes (e.g., dispersal, recolonization), humans could have both

  • exacerbated regional extinctions brought on by climate changes and
  • allowed them to coalesce, potentially leading to the eventual regime shifts and collapses observed in megafaunal ecosystems.

The lack of evidence for larger-scale ecological regime shifts during earlier periods of the Glacial (i.e., >45 kyr) when interstadial events were common, but humans were not, supports a synergistic role for humans in exacerbating the impacts of climate change and extinction in the terminal events.

The paper has a very detailed chart showing declines and extinctions of megafauna of the Pleistocene. (By the way, here's a map of the Holarctic zone from Wikipedia). Click the chart to enlarge it:

Fig. 1 Megafaunal transition events and Late Pleistocene climate records. Major megafaunal transition events (region-wide extirpations or global extinctions, or invasions, of species or major clades) identified in Late Pleistocene Holarctic megafaunal datasets through ancient DNA or paleontological studies, plotted on a reconstruction of Northern Hemisphere climate from the Greenland ice core (GICC05) δ18O record (black wiggle curve). GICC05 interstadial (IS) warming events are shown with light grey boxes. There is an apparent absence of megafaunal events during the Last Glacial Maximum (LGM; blue) and to a lesser extent, the cold Younger Dryas stadial (YD), and a marked association with interstadials. - The caption is very long, there is more detail in the caption in the paper itself. Source: Cooper15

The  animals facing right representing extinctions and those facing left representing invasions. The approximate timing of the first presence of modern humans in North America (New World) and Europe are shown as vertical grey dashed lines.

From the WUWT comments

As you'd expect, a lot of fake sceptics at WUWT uncritically accepted the spin from Eric Worrall and didn't bother checking with the press release or the paper itself. Others put in their two bobs worth about bisons and more. For a change, there were some more thoughtful comments as well.

J. Richard Wakefield
July 24, 2015 at 9:48 am
I wonder if he thinks climate change almost wiped out the bison…

Tom O  wants to shirk responsibility for the current warming:
July 24, 2015 at 1:55 pm
Another way to look at what he is saying, however, is that climate changed, causing the extinctions, but humans didn’t cause the climate change – sort of like what is going on now, you know. climate change not being caused by humans? 

Terry doesn't know much about wildfires. Not the sort of damage that is occurring these days:
July 24, 2015 at 11:35 am
Habitat/forest rarely rarely ever gets “permanently destroyed” ever. That is a fallacy. Plants will start growing immediately after the event. Animals will start moving back into the area immediately. A year later, the only indication will be some burnt remains of trees. You need to rethink your basic understanding of how nature actually works.

Farmer Gez corrects Terry, in part:
July 24, 2015 at 3:57 pm
Not entirely true. Frequent burning eventually changes the flora to favour fire tolerant species. Studies of sediment in Lake George near Canberra shows this clearly. Once you fundamentally change the landscape the species ‘dominoes’ begin to fall.

Pat Ch  points out that we alter the environment through introducing exotic species:
July 24, 2015 at 10:10 am
Humans kill in means other than directly when they migrate. Polynesia is rife with examples of how rats and dogs not only alter the environment directly, but by the introduction of diseases for which the local fauna have no immunity. 
joel draws upon everything he has read, to dismiss this new work but doesn't cite a single scientific paper (it's the norm at WUWT, that people make sweeping unsubstantiated statements like this):
July 24, 2015 at 10:15 am
Everything I have read says the megafauna survived multiple ice ages, only dying out when humans showed up. The fossil record shows all fauna, plant and animal, simply migrated North or South, depending on the temperature.
These people are crazy. Just crazy. That they have any credibility is, or should be, an embarrassment to all of us.

Rob Dawg
July 24, 2015 at 10:22 am
I imagine like in most emerging science that the truth lies in the middle. The megafauna were undoubtably reduced to isolated pockets that might or might not have survived had they not been finished off by human practices; hunting, fire, etc. OR it might have been the other way round where predation (not just humans) isolated pockets that were then finished off by climate change unable to migrate to survivable climates. So much of the period was washed away post glacial or inundated by sea level rise it is surprising we are able to deduce as much as we have.

July 24, 2015 at 11:50 am
One must realize that the mammoth is only one species of many that died out, and not only North America, also the other America’s and Eurasia. Megafauna has also died out at places that are totally devoid of any sign of humans at that time, like for instance the Taymyr peninsula and Wrangel island. We do know that climate changed dramatically in North Siberia, distroying the megafauna steppe.
But that does not explain why camels died out in the Yukon and Alaska thousends of years earlier etc, etc, and why the giant deer died out only some 5000 years ago, let alone the extinction of the European Straight tusked elephant much earlier during the late Pleistocene, like the European hippo’s and rhino’s and the european Sabertooth cat. It’s not that a single species died out at a single place at a single time.

References and further reading

Alan Cooper, Chris Turney, Konrad A. Hughen, Barry W. Brook, H. Gregory McDonald, and Corey J. A. Bradshaw. "Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover." Science, 23 July 2015 DOI: 10.1126/science.aac4315

Mammoths killed by abrupt climate change - press release at ScienceDaily.com

Mammoths Died Out Because of Sudden Climate Change - article by Laura Geggel, Live Science on Discovery News

1 comment:

  1. Nobody there got it that General William Tecumseh Sherman was what doomed the buffalo. Wonder if there's anything new on the breakup of the progenitor of comet 2P Encke and the Taurids core streamings?


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