Talk:Holocene extinction event

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Should that list be sticking to genera (rather than specific species)? Also - is that "39 genera of mammalian megafauna" accurate? Or is this number possibly just for North America?

Also, why are we including only mammals? The teratorn birds appeared to be Holocene extinction victims also, even if they're also described in extinct birds.

Copied from extinction event:

Some people claim that we are living in the middle of another, man-made extinction event right now. However, humanity's effects are trivia compared with the extinction events shown in the fossil record.

Is that a fact? I've seen estimates on damage that are comparable to the smaller or intermediate sized mass extinctions, if nothing like the boundaries that end the Mesozoic and Palaeozoic eras.

If those are the same estimates that I've seen -- that something like 50,000 species a year are dying out -- they are not particularly reliable. The ones I've seen have all been created by organizations like the Sierra Club and people like Al Gore and Paul Ehrlich who have large, flaming political agenda that such figures are constructed to support. Over the past 500 years, almost 90 per cent of the forest along the Atlantic coast of Brazil has been cleared. However, no one has found a single known species that could be declared extinct. According to the "mass extinction" figures, about half the known species in that Brazilian forest should have been lost.
But if you can cite figures commonly accepted by paleontologists -- figures that, say, appeared in a peer-reviewed journal -- feel free to enter them! --The Epopt

Do a search for something like "current mass extinction" in google, and you will find a great number of hits, including articles in Nature and Science. It looks to me like the mass extinction view is closer to a consensus than to a minority of politically motivated views. At the very least there is enough here to remove the sentence from the article, which I'm doing.

This is obviously a controversial topic -- there is nothing like "consensus" in the scientific community -- and I am strongly on the side that says calling what's happening at present an "extinction event" to be listed with the Permian-Triassic extinction event is like calling a domestic quarrel a genocidal holocaust. It's bad, and should be stopped, but blowing it out of proportion is ludicrous. I will fully support and cooperate with presenting both sides of this issue, but please don't try to make it sound like "everyone (who is a true scientist) knows that we're murdering Mother Gaia."

I said that it would be more accurate to say it is a consensus (why quotation marks?) then to pretend the data uncontroversially indicated the converse, as was done, not that it would be entirely accurate. We have had entire families of organisms (not mammals, things like molluscs) mostly depopulated over large areas if not actually rendered extinct, but I'm not interested in debating the point. Simply note that I never said we should make it sound anything like your terrible strawman, I simply said the partisan statement should be removed.
Point taken. I am over-sensitive on this point, and I apologize for my stridency.

Can someone clarify what the rate of extinction needs to be in order to be comparable to something like the Permian-Triassic extinction event? That event, according to the article, lasted on the order of 900,000 years (give or take 600,000 years), with some 70-85% of species dying out. Assuming there were something like 10 million (wild guess!) species at the time, this is an extinction rate of between 4 and 29 species a year, on average. This seems so low that it would barely be detectable if you were in the middle of it. --Zundark, 2001 Nov 29

Your wild guess is right on the money. About one million species of animals have been described. (86% are insects, including about 300,000 species of beetles.) Some biologists estimate that up to 50 million more remain to be discovered. Most estimates put the number of plant species at somewhere between 10 million and 30 million, with tentative consensus around 14 million. I have no idea how many more plants they think have not been found yet. So your point is very well-made -- if humanity continues its current rate of eliminating species for another million years or so, we will be as bad as whatever clobbered Earth at the end of the Permian.
Though this is a case of the apparent support for one side being rather more destructive of the argument than helpful :) A million years at our current pace...wow, I'd never have guessed. I plan on filing this away in my cranium for future (currently vague) use. Probably "Want to know how bad the Permian extinction was" not "We humans aren't so bad", though.

I removed

from the list of Holocene extinction victims only because they are already included under extinct birds.

So far as extinction of megafauna is concerned, the climate change hypothesis is becoming less and less tenable as time goes by. It's not too difficult to make a reasonable case for climate change as the primary factor if you look at any particular instance, but looked at as a whole, it doesn't make sense.

  • Almost all the American megafauna went extinct about 13,000 years ago, three others survived perhaps a couple of thousand years longer.
  • The Australian megafauna, on the other hand, didn't survive anything like that long: there are still nagging issues with claimed exceptions here and there (as there always are in issues of this kind) but the weight of evidence decisively favours an extinction date of ~ 50,000 years ago.
  • New Zealand megafauna, on the other hand, survived right up until ~ 400 years ago.
  • The giant birds of Mauritius also survived all the warmings and the coolings, only to perish within historical times.

And so on.

I am not suggesting that climate change be ignored as a factor (far from it: it still has many proponents), nor that it has not been an enormously significant factor in many things, simply advocating that the entry on this question more accurately reflect the current state of knowledge. Tannin

from wikipedia:pages needing attention - "Holocene extinction event - more species are needed, and some help with NPOV" - unsigned, undated comment - probably ignorable. Martin

It does need work, and is on my to-do list - alongside 14,978 other things, at last count - but the POV problems were pretty much dealt with three or four months back. It's a bit wish-washy now, but broadly OK.

BTW, Martin, don't let my reverting you on this one POV warning put you off - I think your working through the old notices and lists is a really, really useful thing. There is no harm in being bold when (as is your habit) you are happy to accept the odd disagreement in good spirit. Better, for a job like that one, to just go ahead and make some wholesale decisions on the theory that 90% of them will be right, and someone else will pick up on the 10% of retail errors and deal with them appropriately. Tannin 13:15 May 12, 2003 (UTC)

Thanks Tannin - always nice to have some positive feedback :) Martin

Evidence exists for a large, possibly multiple meteor or comet strike at 7640BCE, with a smaller one at 3150BCE. The evidence include stratigraphic studies of tektites, dendrochronology, and ice cores containing nitrates caused by extreme heating of air. This evidence is consistent with the dates of formation of a number of salt flats and lakes still extant in dry areas of N. America and Asia, suggesting that the strikes may have occurred in oceans, causing multiple-kilometer-high waves that penetrated deeply into continents. Incursions of salt, sand and oceanic fossils in this period were classically explained by "depression" of continents by the weight of Pleistocene ice, but these explanations are inconsistent with countervailing observations of a 30-120m rise of ocean levels at the same time. Can someone come up with a suitable title where we can put this? It's connection with the Holocene extinction event is minimal. Wetman 07:00, 5 Apr 2004 (UTC)

Here is a link that explains one of these "references": Tollmann, Alexander and Edith, Terra Nova 6, pp. 209-217, 1994:" "Giant Comet launched Noah's Ark"

Terra Nova is a perfectly respectable peer-reviewed European academic journal of geology. See www.blackwell-synergy.com. Just because its not popular to believe in the Noah's Flood doesn't make it false. Stodgy references to tektites and acid in ice cores are pretty persuasive, actually.

From the timing, the comet strike initiated the Holocene, and probably has a better claim to the title than the information about species. The loss of species is significant, and deserves its own article, not tied to the current geological age- after all, it's a recent historical process. User:Ray Van De Walker

But it is popular to believe in the Flood. And it's very popular to attribute everything to bolide events. We shall see. They laughed at Alvarez. But as for the evidence Tollmann is all over the map! Wetman 08:08, 5 Apr 2004 (UTC)
Guilt by association is an ad hominem argument. As a real skeptic, you can do better. Falsify it. User:Ray Van De Walker
I've given this its own entry, Tollmann's hypothetical bolide with a reference at Bolide. Wetman 17:39, 5 Apr 2004 (UTC)

Is the "Holocene extinction event" a scientific expression at all? I could not find any single article that includes "Holocene extinction" in its title nor abstract in 61 journals including Nature, at the following search form. http://www.nature.com/dynasearch/app/dynasearch.taf?

There are many articles that scientific articles that include "Holocene extinction", just search with http://scholar.google.com Another name often used is the "Sixth extinction event". Peter Maas 18:58, 23 October 2006 (UTC)

Contents

[edit] Frogs

Foant added: About half of all frogs (amphibia) have become extinct during the 20th and 21th centuries due to unknown causes but pollution of water, global warming has been proposed as a factor. Three quarters are endangered.

I can't find any support on google for half of either frogs or amphibia having already become extinct. Certainly they are highly vulnerable, but to claim that half are already extinct seems excessive. Unless you have a reference to support this, I am going to remove it. Dragons flight 17:39, Apr 30, 2005 (UTC)

Ok, here is the sources I found (wrote that above from memory): http://www.dn.se/DNet/jsp/polopoly.jsp?d=597&a=344210 (swedish), http://www.washingtonpost.com/wp-dyn/articles/A33569-2004Oct14.html, http://web.archive.org/web/20011129072744/www.oregonlive.com/news/00/02/st021910.html , http://www.worldwatch.org/press/news/1998/05/21/ . Well it seems they are in decline and some are already extinct... After you have read the sources maybe you can phrase it better than I did? Foant 18:06, 2005 Apr 30 (UTC)

The Holocene extinction event is a name customarily given to the widespread, ongoing extinction of species occurring in the modern Holocene epoch.

The statement that there is a "widespread, ongoing extinction of species" is not supported.

What is the current estimated rate of extinction? How does this differ from historical norms? Is there a historically normal rate of extinction or does the rate tend to fluxuate wildly?

How do scientists estimate the current and previous rates of extinction? do these estimates tend to be the same, or do they vary widely depending on the methods used and the scientists conducting the study? What does this imply about the accuracy of these estimates?

The fact that many species of large animals became extinct between 13,000 and 9,000 years ago is troubling. However, comparing it to say, the Late Devonian extinction, where 70% of all species on earth became extinct is a bit overdramatic.

In its attempt to link these extinctions with the presence of human beings, the article also glosses over the fact that the last ice age ended 10,000 years ago, and that climate change is a common cause of extinction. Might it be more accurate to say that human behavior is one of several causes of the current extinction event? (Assuming, of course, that an extinction event is in fact taking place.)

Well, I can asure you it is taking place! Just visit my website: http://extinct.petermaas.nl Current climate change is different from other periods, that it is caused by human behaviour now! Another site I cn recommend is: http://www.iucn.org/themes/ssc/red_list_2004/main_EN.htm And the 2004 IUCN Red List of Threatened Species - A Global Species Assessment: http://www.iucn.org/themes/ssc/red_list_2004/GSA_book/Red_List_2004_book.pdf In this pdf also more info and data on (frog)extinctions caused by climate change. Pmaas 11:42, 15 December 2005 (UTC)

From the above mentioned IUCN pdf: Only 34 amphibian species are recorded as having become Extinct by the 2004 IUCN Red List of Threatened Species, 20 of these being endemics to Sri Lanka, most of which disappeared over 100 years ago. It is likely that there have been many undetected amphibian extinctions over the last two centuries, and the concentration in Sri Lanka, although real, is also a reflection of the detailed taxonomic studies of frogs that have taken place there. Nine of the 34 amphibian extinctions have taken place since about 1980. Eight of these nine recent extinctions were sudden disappearances in suitable habitats, and are probably the result of the fungal disease, chytridiomycosis, probably operating in conjunction with climate change (Laurance et al. 1996; Berger et al. 1998; Ron et al. 2003; Burrowes et al. 2004). However, these figures are probably a very large under-estimate of the level of amphibian extinctions since 1980. A total of 122 amphibian species are listed as Critically Endangered (Possibly Extinct), and 113 of these could have disappeared since 1980. Most of these took place in Central and South America, in particular from southern Mexico south to Ecuador, with others recorded from Puerto Rico, Hispaniola, Jamaica, Venezuela, and southern Brazil. Other possible extinctions have been noted in Australia, Indonesia, China, Kenya, and Tanzania. Most of the disappearances happened very suddenly, and it seems increasingly likely that chytridiomycosis, linked to climate change, is the main cause. Proving extinction beyond reasonable doubt is often very difficult. Pmaas 11:48, 15 December 2005 (UTC)

Regarding "The Ongoing Holocene Extinction", please cite articles from peer-reviewed journals that indicate 1) how current human activity is causing extinction of species 2) the extent to which species will be extinct as a direct result of such activity in the near future. "Those who are skeptical about the impending mass extinction" will need convincing.

Not very familiar with this topic, and not a native english speaker, I didn't want to edit this myself, but I believe it is a typo of some sort:

For instance, the timing of sudden megafaunal extinctions of large Australian marsupials and a giant lizard, events that followed the arrival of human beings in Australia by many thousand years, need examining.

Shouldn't "followed" be replaced with "preceded" or something? Feel free to remove this comment if you're convinced I'm wrong. --Jacob no. 9 19:58, 26 February 2006 (UTC)

In a word, no. It isn't a typo, it's just a plain old mistake. Current evidence supports the exact opposite conclusion - i.e., the mass extinctions are believed to have immediately followed the arrival of humans on the continent. Tannin 04:53, 6 May 2006 (UTC)

[edit] North American Genera/Species

The section on Pleistocene extinctions in North America has the following

Circa 12,000-9000 years BP, 35 to 40 species of large mammals, while only about half a dozen small mammals, disappeared[citation needed].

I changed species to genera, and this change was reverted. I thought I would discuss my reasoning for this change here. I should note that elsewhere in the article, 33 genera of megafauna go extinct in the late Pleistocene.

Generally, the literature I am familiar with (Grayson 2001, J. World. Prehist. 15:1-63 for example, but many others) cite 33 - 35 genera of megafauna which go extinct. Some authors believe (Alroy 2001, Martin 1973, Mosimann and Martin 1975) that the extinctions occured in a short time scale, during Clovis time. Archaeologists who work on this time period (Grayson and Meltzer 2003, for instance), however note that there is little archaeological evidence for this sudden extinction. While biological modelers do recognize this, they can attribute it to the Signor-Lipps effect. Thus it is not uncontroversial to argue that 33-35 genera went extinct in Clovis time (usually about 12,250 - 10,500 rcybp), this is argued by some. This is all analysis done at the genus level.

At the species level, there is little coherance. I don't have an immediate citation off the top of my head (I'll look around later), however the recognition of different species in the same genera is dodgy at best. Experts disagree about what consititutes a new species, and thus they disagree about species counts. Thus most of the analysis is done at the genus level. Thoughts on how to improve this section? --TeaDrinker 22:25, 30 June 2006 (UTC)

i think everything you ve said is on target. the obvious addition we need to make is more on plants and lower life forms in general. As far as your comment on genrera vs species (and you are totally correct of course), the problem here is the lay public is used to thinking in species terms, and has a very difficult time grasping the significance of a lost genus. so we need to have some kind of dialog at the species level. Anlace 22:48, 30 June 2006 (UTC)
I am the one who reverted and asked for a citation. Basically, I was bothered by the 3000 years because I couldn't believe we had that good an age control (and we don't). I've now updated the section based on a 2004 review by Barnosky et. al in Science. According to their figures, only about 1/2 of the genera can be reliably attributed to this interval. While Signor-Lipps might allow more to fall in that interval it is not appropriate on the basis of current knowledge to say for sure that they do. Dragons flight 23:30, 30 June 2006 (UTC)
Great work, I think you hit the nail on the head. I took the liberty of removing the Grayson citation since he does not mention how many smaller animals went extinct. I will try and find a citation for it, however (although I am not certain the number is correct). --TeaDrinker 06:31, 1 July 2006 (UTC)

[edit] "Millions" of species

Anlace recently added:

These estimates rely upon an annual loss of up to 140,000 species per year (based on Species-area theory).

based on S.L. Pimm, G.J. Russell, J.L. Gittleman and T.M. Brooks, The Future of Biodiversity, Science 269: 347-350 (1995).

However, while this reference predicts substantially accelerating in the future, they plainly estimate the extinction rate over the last 100 years as 20-200 extinctions per million species year. In other words, given 10-100 million species, that amounts to no more than 20,000 species per year and a more middling value might be 2,000. I don't see how you can possibly get 140,000 from that paper, except possibly by trying to apply the species-area relationship to some numbers not appearing in that paper.

Also, this is not really the kind of citation I'd like to see in support of "millions" of extinctions. It would be much better to point to a reference claiming directly that millions of extinctions have occured. If the middle value is something like 200,000 extinctions during the last century, then while millions of extinctions might be possible, it is not necessarily likely. Hence, the first thing to do is establish that there really are some scientists, somewhere, who plainly estimate there have already been millions of extinctions. Or perhaps we should clarify the existing text to say something like: "Scientists estimate that during the last century, between 20,000 and two million species have gone extinct but the precise total cannot be determined more accurately within the limits of present knowledge." Dragons flight 05:53, 1 July 2006 (UTC)

[edit] Cleanup/Split

This article is confusing. It seems to be describing two separate events - the Pleistocene extinction and the Holocene extinction. I'm really not sure how to begin to clean it up, but I feel that as well as being cleaned up it should either be moved to a name which reflects this dual nature or else split into two separate articles. I know I was confused when I clicked on "Pleistocene extinction event" and it redirected here. If anyone has any suggestions please make them known. --72.140.146.246 03:03, 2 August 2006 (UTC)

if there is a split, Pleistocene extinction event would be a sub-article to Holocene Anlace 02:05, 5 October 2006 (UTC)

[edit] Split: New World Pleistocene Extinction

I have created a page New_World_Pleistocene_Extinctions and linked it to the Holocene extinction event page. My specialty is New World others with other specialties might want to do pages on other parts of the world. Then an overview - Pleistocene extinction event page would be appropriate. Oct 25, 2006. User:ElinWhitneySmith

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