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Sixth Mass Extinction - paper

  1. Jun 23, 2015 #1

    jim mcnamara

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    Accelerated modern human–induced species losses: Entering the sixth mass extinction
    Gerardo Ceballos, Paul R. Ehrlich,
    Anthony D. Barnosky, Andrés García,
    Robert M. Pringle and Todd M. Palmer

    Science Advances 19 Jun 2015:
    Vol. 1, no. 5, e1400253
    DOI: 10.1126/sciadv.1400253

    This paper posits that we humans are in the midst of a current mass extinction, caused by human activity.
    This paper has already come under attack from a political point of view. Let's not do that.

    My question is: can someone validate/invalidate the scientific merits of the claim? I am not able to do that.
  2. jcsd
  3. Jun 23, 2015 #2
    That species are being lost and that some of this is an effect of human activity is I think reasonably indisputable.
    When it comes to terms like '6th mass extinction' though, personally I consider that to be somewhat of an arbitrary value judgement.
    Too loose and emotive, for me, - at what rate of species loss is it a 'mass extinction' as oppossed to just extinction, and there will always be some number of species going extinct.
  4. Jun 24, 2015 #3

    jim mcnamara

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    That is what the paper is all about - determining what extinction rate marks mass extinctions. It does not appear to me to be an easy determination to make. We are watching extant species go extinct, versus fossil evidence. It is hard to determine rates of anything based on fossil deposits. You can see extinctions on a grand scale in some strata. But were they over a period of a few million years or 100000 or even less? rate=loss/year. That is too fine grained to apply to the top 10m of a deposit that persisted over an extinction of a set of marine fossils - for several million years. In other words it is a sampling problem. We can do a decent rate determination on today's beasties rates of extinctions. Doing the same on Creataceous ones is lots harder....
  5. Jun 24, 2015 #4

    As a paleontologist I find it all somewhat human hubris and hype.

    Firstly, there are no set number of mass extinctions. All speculative and arbitrary. Really, really, really speculative to the point where it becomes meaningless.
  6. Jun 25, 2015 #5

    jim mcnamara

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    That was also my take on it - a very difficult task to do at all. Sometimes stuff like this, when it hits the news feeds, does not help the image of Science. My opinion only.
  7. Jul 14, 2015 #6


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  8. Jul 23, 2015 #7


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    The fossil record is a highly suspect source of extinction data. We have no idea how many species actually existed vs how many species appear in the fossil record; nor do we know the relative abundance of those that do appear in the fossil record. A fossil is the poster child for selection bias. It is a lucky accident- a critter must croak under conditions favorable to the fossilization process without being scavenged or disinterred before fossilization. We pretty much only have fossils of critters that happened to meet the reaper in aquatic environments, like oceans, lakes, swamps, etc. The odds of finding a fossil of critters not indigenous to such environments is remote.While I applaud the authors intent to quantify the evironmental impact of human beings, I fear they have only contributed another weapon to the arsenal of environmental extremists. The mere presence of human beings displaces other creatures evolved to fill the environnmental niches we occupy. Let's not lose sight of, for example, how many life forms are utterly dependent on human sewage for their survival. We could very well be the base of one of earths largest food chains. Nature is too robust to leave any environmental niche unoccupied for very long.
    Last edited: Jul 23, 2015
  9. Jul 23, 2015 #8


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    Since I know nothing about this subject, I'll just make a trivial remark: Why "mammal and vertebrate extinctions" and not just "vertebrate extinctions"?
  10. Jul 23, 2015 #9


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  11. Jul 23, 2015 #10
    Right off...the abstract is wonky.

    Vertebrates do not equate with mass extinctions. Vertebrates are one of several animalia phyla and not all that significant in the scheme of things. Arthropods are multiple times more numerous in all aspects....what is their status? What about Molluscs? Coelenterates?

    Even animalia don't dominate life. We have no idea if there are 2 billion types of bacteria or 3 billion, so how do we measure some mass distinction? Ecosystems don't have gaps for more than a few seconds...bacteria, a virus, spore, etc. are opportunistic.

    Extinctions are not really a scientific concept outside of strict parameters. There is not less variety of life today than 100 years ago and there will be as much variety a hundred years from now even if humans ceased to exist.
  12. Jul 23, 2015 #11

    I think your intuition is correct that your paper will be viewed politically and I think you would benefit from clearly separating your claims and looking at their proof independently if your paper is to survive the inevitable attacks.

    My respectful suggestion would be that you firstly you establish a strong, self-standing and credible basis for the claim that current profile of extinctions is part of a mass extinction. For example; what suggests the trend will continue? Is it mass/random or species selective? What's the uncertainty in the data you're using, and just as importantly what is the credibility of any other claims you are building on? What other outcomes have you considered (e.g. life is good and the data is just noise) and why have you rejected these conclusions?
    i.e. what is the data / evidence that underpins your claim, and what are the logical arguments that lead you to the conclusion of mass extinction, as opposed to any other outcome?

    Once you have demonstrated the validity of the first claim, you can then move onto your second claim - the cause is human - and a similar process is needed to the above. For example; what aspect(s) of human impact are the cause and how do we support this? If (to choose a really bad and trivial example) you were to conclude that it was all down to human generated pollution then you would have to be able to show data that proved the extinction started after humans started polluting. As above; you will need to have just as good arguments to discount other causes of mass extinction as you do for supporting the human cause. If you only major on the case "for" and don't fully refute the case against each of the other options; you lay yourself open to logical fallacy arguments which can undermine your credibility even if you are 100% correct - see much overused example below:

    Conclusions: Killing Pirates causes global warming? Global warming kills Pirates? Global Warming and Pirate Decline have a secret common cause? None of the above?
    The answer is... until you've done the analysis you can't discount/support any of the conclusions. (and replace the axis with Species Extinctions and Human Environmental Impact and you have the challenge ahead of you!)

    Hope this has come over as constructive as it was intended. Best of luck in your endeavor.
  13. Jul 23, 2015 #12


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    Is the fact that we are continuously finding and losing subspecies taken into account, or is only the extinction of such species taken into account, I'm a bit confused on this part. But I mean, I guess one could call huge natural disasters in certain areas mass territory extinctions right? Unless they already have a better/established name for it. :-p
  14. Jul 23, 2015 #13
    Great example.

    The issue with man's impact on the environment, climate change, etc. is not the validity or not. It's the lack of scientific methodology. There are so many variables that it's impossible to know what to measure and what weight to give a variable. What is the base line for each variable? How is that baseline verified by published studies in accepted journals? All completely impossible.

    Many variables can be chosen (pirates) and the math works. There has been an increase in computer use...decline in Am radio transmissions...many things can be put on a graph to correlate with increased fossil fuel consumption.

    I have no issue with studies that try and analyze trend setting as long as they are under some title as 'educated speculation' and not 'science'.
  15. Jul 24, 2015 #14


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    Relying on marine fossils is not very helpful for quantifying biodivesity
  16. Aug 5, 2015 #15
  17. Aug 5, 2015 #16
    The following quote:
    ...The Ehrlichs stand by the basic ideas in the book, stating in 2009 that "perhaps the most serious flaw in The Bomb was that it was much too optimistic about the future" and believe that it achieved their goals because "it alerted people to the importance of environmental issues and brought human numbers into the debate on the human future.(Source: wiki population bomb https://en.wikipedia.org/wiki/The_Population_Bomb), reflects, in my opinion, the fundamental flaw in thinking behind population growth (the universal laws of growth/development and evolution). If we look at the Sigmoidal growth curve for example, it has a lag phase, an exponential and finally a much slower phase. Being universal, this implies that populations will stabalise naturally as the exponential phase always calms down. For instance many studies have been done to show that more affluent countries tend to have less children (personally I would be more worried about depopulation issues), while, poorer third-world country's tend to have more children. For the physics behind my assertions please click on the following article only posted a few days ago entitled: Alternative Evolution: something universal is going on... http://diggingupthefuture.com/2015/08/03/evolution-scaling-laws-something-universal-is-going-on This evolutionary article is all about the laws and principles of growth and evolution as applied to the fossil record and in a nut shell, shows why the population bomb has never exploded and may never do so, even if the prediction was wrong in terms of when!
  18. Sep 25, 2015 #17
    While its clear that humans have been involved in the extinction of certain species, Its suggested that most have involved island species where humans introduced new species during the period of exploration. Extinction rates have probably fallen markedly since then. Really its impossible to have a clear answer, we don't even have a clear idea about the number of species there are. Humans have also been active in the preservation of animal habitats. This idea is alarmism based on poorly informed guess work.
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