Do species disappear naturally or is it all due to man's impact on the planet?

Great Debates
41

[QUOTE=intention]
Someone asks if I am saying that we should continue to cut down forests indiscriminately. No, absolutely not, that would be a bad idea for a host of reasons. It’s just that history has shown us that extinction is not one of those reasons.
[/QUOTE]
Along with Blake, I really can’t believe your data actually supports your assertion without weaselling, but even if it did, I still think you’re extrapolating something unreasonable about it - to wit - because reduction of forest habitats (allegedly) have not caused extinction, extinction is not an expected result of continued reduction.

I know you said you don’t think we should continue to cut forests indiscriminately, however, what you’re saying amounts to the assertion “we shouldn’t, but it doesn’t matter if we do”.

42

[QUOTE=Blake]
Dude while I agree with the major thrust of your post, you can’t just post nonsense like this. Many birds and mammals have become extinct though habitat reduction. For Australia alone I can name the paradise parrot, eastern hare wallaby and lessers stick nest rat. For Europe I can name the aurochs. For Asia the Himalayan Quail. All are species that have become extinct as a result of habitat reduction.

Are you saying that aurochs isn’t extinct, or that it wasn’t a forest animal?

[/quote]
Are you not reading what I write? Or perhaps I am not being clear. I had specified continental mammals and birds, and specifically excluded Australia and islands.

Onwards. The Red List has never heard of an extinct bird called the “Himalayan quail”. The only extinct quail was from New Zealand. There is a Himalayan Quail, but the Red List says it’s not extinct … although you might have more recent information than they have.

Nor is the aurochs extant in the Red List. Why? For that we can turn to the Committee on Recently Extinct Organisms of the American Museum of Natural History (CREO) , which actually carries more scientific weight than the Red List. They say it is:

and

and thus was not even considered. It is extant in hundreds of subspecies as Bos taurus, the common barnyard cow.

Don’t like that? Don’t argue with me, bro’, go argue with the stupid boneheaded PhD extinction specialists at the American Museum of Natural Hisory.

The only thylacine I’m familiar with is the “Tasmanian Tiger”. It was native to Australia and Tasmania.

And like the overwhelming number of extinct species, it was intensely hunted by another introduced species, in this case, the dogs that came to Australia with man …

Here’s the deal. You have islands, or even larger bodies of land like Australia, that have existed in isolation from the world, with a certain limited number of species for millions of years. Then, after being isolated for all that time, some new species gets introduced. Rats were introduced to Hawaii, brown tree snake to Guam, dogs to Australia, humans to Mauritius. And in all of these cases, extinctions ensued, of dodos and tree nesting birds and thylacines and dodos. After millions of years on their own, any new species can wreak havoc on an isolated island.

But bird and mammal extinctions from habitat reduction on the continents? We have no record of that happening. Here’s all of the known continental extinctions along with their proximate causes:

Bluebuck, Hippotragus leucophaeus, 1800 - Red List says " … hunted by European settlers throughout the 1700s. The last of the species was killed around 1800."

Labrador Duck, Camptorhynchus labradorius, 1878 - “Shooting and trapping on the winter quarters were certainly proximate factors in the species’ extinction. Overharvest of birds and eggs on the breeding grounds could also have been a factor.” (Red List)

Algerian gazelle, Gazela Rufina, 1894 - Reason for extinction unknown, this species known only from an adult male skull and a flat skin “probably somewhat stretched,” collected “many years ago;" type locality given as “Interior of Algeria” by Thomas (1894:468). (CREO)

Carolina Parakeet, Conuropsis carolinensis, 1904 - Hunted for food and the millinery trade, killed for crop protection and because it competed with bees. (Red List)

Slender-billed Grackle, Quiscalus palustris, 1910 - “It had a small distribution in the Lerma marshlands, in the state of México, Mexico … last recorded in 1910, and presumably became extinct soon after as a result of the draining of its tule-cattail and sedge habitat.” (Red List)

Passenger Pigeon, Conuropsis carolinensis, 1914 - “… Newcastle disease, extensive hunting, and the breakdown of social facilitation.” (Red List)

Colombian Grebe, Podiceps andinus, 1950s - " … wetland drainage, siltation, pesticide pollution, disruption by reed harvesting, hunting and predation by introduced rainbow trout Salmo gairdneri." (Red List)

Atitlán Grebe, Podilymbus gigas, 1986 - “Its population dropped from c. 200 to 80 as a result of competition and predation by large-mouth bass Micropterus salmoides, introduced into the lake in 1960, but recovered to a high of 232 in 1975 when the numbers of bass plummeted. However, increasing pressure on breeding sites from local reed-cutting and from tourism development, along with the murder of the government game warden for the national park during the political unrest of 1982 and falling lake levels following the earthquake of 1976, drove the population down to 30 by 1983, and extinction by 1986. Drowning in gill nets and disturbance by increasing boat traffic have also been suggested as contributory factors.” (Red List)

(Interestingly, this bird has since been replaced on Lake Atitlan by a similar grebe of the same genus, P. podiceps. In fact, there is significant disagreement among biologists about whether Podilymbus gigas is just a subspecies of P. podiceps, but I have included it to be on the safe side.)

Omilteme cottontail rabbit, Sylvilagus insonus, 1991 - Reason for extinction unknown, species known only from 3 specimens collected in 1991. (CREO)

And that is the entire record of continental extinctions, 3 mammals and 6 birds. As the record shows, despite all of the forests we’ve flattened over the last five centuries, no forest birds or mammals have gone extinct.

But I digress, this is all a side issue, the real question regards the mythical ongoing 6th wave of extinctions. I notice that nobody has taken me up on my invitation to name a few of the hundreds of mammals and birds that are claimed to have already gone extinct from forest reduction. Remember, according to E. O. Wilson and his adherents, there should be about a thousand continental birds and mammals that have already gone extinct.

w.

43

[QUOTE=Mangetout]
Along with Blake, I really can’t believe your data actually supports your assertion without weaselling, but even if it did, I still think you’re extrapolating something unreasonable about it - to wit - because reduction of forest habitats (allegedly) have not caused extinction, extinction is not an expected result of continued reduction.

I know you said you don’t think we should continue to cut forests indiscriminately, however, what you’re saying amounts to the assertion “we shouldn’t, but it doesn’t matter if we do”.
[/QUOTE]
Mangetout, thank you for your post, but please don’t put words in my mouth. And please don’t imply that I am a weasel, it’s unbecoming of you. Pick another word.

I must say, though, I admire your take on this. You really “can’t believe” my data, but offer none of your own. You have provided nothing that contradicts anything of what I am saying. I have given you a way, using the Red List, to determine the veracity of my claims. Obviously, you have not even bothered to do the homework, or you’d know that my claims are backed up 100% by the Red List and the CREO. Are you fighting ignorance here, or merely restating your belief system?

What I said was clear. It is a Bad Idea™ to wantonly cut down forests, and I listed a number of reasons why in my post above. There are many more reasons, I grew up in the middle of a large forest and they are wonderful things from a host of perspectives, from the practical to the spiritual. It matters very greatly whether we cut them or not.

It just doesn’t seem to matter to the number of extinctions.

Do I expect extinctions if there is continued forest reduction? Possibly so, but remember, we’ve cut down somewhere around a third to a half of the world’s forests in the last five hundred years without seeing a single continental forest mammal or bird extinction. So if we do see extinctions, I would expect them to be few in number.

The key is this. The scientific theory that this is all based on says that as the area of a particular habitat falls by any amount, it will cause extinctions. Not that it will only cause them when 93% of the habitat is gone. Not that there will be no extinctions until we get to 60% reduction and then we’ll see lots of extinctions.

The theory says that the number of species varies as some power of the area, and if you reduce the area even by only say 10%, you will see extinctions. We have been engaged in a 500 year deforestation experiment which tested this theory, and the results of the experiment are clear - the expected extinctions simply do not happen in the mathematically determined manner claimed. If they did, we’d have seen hundreds of continental forest birds and mammals go extinct in the last half millennium … but we have none. We wouldn’t be here discussing whether one species was extinct or not, we’d be looking with dismay at hundreds of extinct birds and mammals.

And that’s my point. The claimed 6th wave of extinctions simply is not happening. For whatever reasons, the species-area theory doesn’t seem to work in reverse as claimed. Extinction rates have been dropping over the last hundred years, not rising.

w.

44

I’m sorry that my choice of words offended you. However, I think you’ve misunderstood me in several ways, including those on which you took offense.

I’ll confess I’m not familiar with the theory of extinctions you describe here (and appear to be inviting me to defend). I wouldn’t expect it to work like that anyway, but I’m not an expert on any of these matters, so I’m just going to shut up.

45

It’s interesting how small the CREO list is - 171 animals total. And many of them are vermin - mice, rats, bats etc - and is it really significant if one species of rat becomes extinct? It’s sad that the red squirrel is being replaced by the black squirrel, but little more.

But when I look at that list, I find myself thinking of all the nearly-extinct species, like rhinos and tigers. So the CREO list is not the whole story.

46

[QUOTE=Quartz]
But when I look at that list, I find myself thinking of all the nearly-extinct species, like rhinos and tigers. So the CREO list is not the whole story.
[/QUOTE]

I notice that the ivory-billed woodpecker–a continental forest species long considered extinct due to habitat reduction–is listed only as “critically endangered,” as if its controversial rediscovery of a few years ago had been confirmed, which to the best of my knowledge is still not the case.

47

[QUOTE=intention]
So y’all can ramble on about the huge extinction that is going on. Me, I’ve got this odd proclivity to look for that thing called “evidence” … I know that’s old-fashioned, but I’m just a reformed cowboy so I’m kind of old-fashioned myself.
[/QUOTE]

You do realize, do you not, that what you are arguing against is Wilson’s extrapolation of the species-area relationship to extinction numbers, not that the current rate of extinctions does not exceed the background rate? I, myself, am skeptical about applying the relationship across ecological zones, and the term “forest” can apply to several such zones which should not necessarily be lumped together to arrive at a single area for evaluating expected diversity. That, and the fact that the constant C in the species-area relationship formula is not constant across ecological zones, and can often vary by several orders of magnitude between them (unlike the z coefficient, which only varies between around .15 - .50, regardless of zone). As such, any hard numbers that are coming from estimated species numbers for very large areas (wherein one could reasonably argue that the extent of the area does not represent a unified ecological zone) are suspect, at best.

However:

The “background extinction rate”, based on analyses of the fossil record, is typically cited at approx. 1 species / million species / million years, or from 10-100 species per year (note that this value is for all species). For mammals alone, the rate is approximately 1 species every 200 years.

The Red List’s summary of extinctions by major taxonomic group shows 74 mammal extinctions since about 1500 CE. This is over 29x the estimated background rate. However, an additional 163 mammal species are critically endangered, and 349 more are endangered. Were these groups to go extinct within the next 100 years or so, the extinction rate would skyrocket to over 195x the background rate (from 1500 CE - 2100 CE, the expected number of mammal extinctions based on the background rate would be…3 species).

Thus, the evidence does, indeed, support a higher-than-background extinction rate over the past 500 years or so, at least. It may not be as dramatic as Wilson, et al, are claiming, but it is not a figment.

48

[QUOTE=Darwin’s Finch]
You do realize, do you not, that what you are arguing against is Wilson’s extrapolation of the species-area relationship to extinction numbers, not that the current rate of extinctions does not exceed the background rate? I, myself, am skeptical about applying the relationship across ecological zones, and the term “forest” can apply to several such zones which should not necessarily be lumped together to arrive at a single area for evaluating expected diversity. That, and the fact that the constant C in the species-area relationship formula is not constant across ecological zones, and can often vary by several orders of magnitude between them (unlike the z coefficient, which only varies between around .15 - .50, regardless of zone). As such, any hard numbers that are coming from estimated species numbers for very large areas (wherein one could reasonably argue that the extent of the area does not represent a unified ecological zone) are suspect, at best.

However:

The “background extinction rate”, based on analyses of the fossil record, is typically cited at approx. 1 species / million species / million years, or from 10-100 species per year (note that this value is for all species). For mammals alone, the rate is approximately 1 species every 200 years.

The Red List’s summary of extinctions by major taxonomic group shows 74 mammal extinctions since about 1500 CE. This is over 29x the estimated background rate. However, an additional 163 mammal species are critically endangered, and 349 more are endangered. Were these groups to go extinct within the next 100 years or so, the extinction rate would skyrocket to over 195x the background rate (from 1500 CE - 2100 CE, the expected number of mammal extinctions based on the background rate would be…3 species).

Thus, the evidence does, indeed, support a higher-than-background extinction rate over the past 500 years or so, at least. It may not be as dramatic as Wilson, et al, are claiming, but it is not a figment.
[/QUOTE]
Darwin’s Finch, thank you for a thoughtful post.

You are correct that I am making two separate arguments. One is that Wilson’s extrapolation of the species-area law does not work in reverse (to predict extinctions) on the continents.

You seem, however, to have misunderstood my second argument, which is that the extinction rate on the continents is not very different from the historical rate.

Curiously, comparing extinction rates across time is not a simple task. We can’t simply compare modern extinctions with historical extinctions as you have done above. This is because the means of discovering the two are so different (direct observation vs. examining the fossil record). Since we are here now and we weren’t there then, we would expect to discover more modern extinctions than we would discover by looking at fossils.

Instead, we have to ask ourselves a slightly different question - what would an archaeologist a million years from now calculate as the extinction rate (for continental birds or mammals) for our time? We need to determine whether future paleontologists looking back at our fossil record would say our era was above or below the background rates. That way we are comparing apples and apples.

To calculate this uncertain figure, it is useful to use “fuzzy sets.” Traditional set theory includes the idea of exclusively being or not being a member of a set. For example, an animal is either alive or dead. However, for a number of sets, no clear membership can be determined. For example, is a person “old” if they are 55?

While no yes/no answer can be given, we can use fuzzy sets to determine the ranges of these types of values. Instead of the 1 or 0 used to indicate membership in traditional sets, fuzzy sets use a number between 0 and 1 to indicate partial membership in the set.

Fuzzy sets can also be used to establish boundaries around uncertain values. In addition to upper and lower values, these boundaries can include best estimates as well. For example, the number of mammalian species is given by the IUCN as 4,629 species. However, this is known to be an estimate subject to error, which is usually quoted as ± 10%.

This range of estimates of the number of mammal species can be represented by a triangular fuzzy number written as [4166, 4629, 5092], to indicate the upper and lower bounds, as well as the best estimate .

Fuzzy numbers can be used in place of regular numbers in any type of calculation, and the resulting uncertainties propagate through the calculation. If this is done across all membership values, the result is a fuzzy number showing the range of expected answers. (See the excellent work by Regan et. al. for a full explanation of these concepts.)

To use fuzzy numbers to compare extinction rates of continental mammals, we first have to determine how many of the 3 extinct continental mammal species will likely make it into the fossil record. Only one of the species (Bluebuck) was at all widespread, so the best estimate is that 1 species would show up in the fossil record. The low estimate would be that none would make it, and the high estimate would be 4, to allow for an extinct species that we might have missed. So the fuzzy number of extinct species found in the future fossil record for our times would be [0,1,4].

Next, we need to estimate the total number of continental species present in the future fossil record. We first need to estimate how many continental species there are, and then figure how many of them will make likely make it into the fossil record.

According to the IUCN, the number of mammal species endemic to islands is 581, with an additional 206 mammals endemic to Australia, for a total of 787. The lower limit, then, would be 787 species not in the record (less 10%, as this number is inexact and we want the smallest possible value). In addition, some endemic continual species will likely not make it into the record. A reasonable upper limit would be the total number of endemic mammal species, or 1,884 species + 10% uncertainty. The most likely number is probably around 1,200 species, so the fuzzy number we need to subtract from the total count of species is [708, 1200, 2072].

Our calculation of the observed extinction rate (OER, in species/year) for the last 500 years, then, is:

OER = ( [0, 1, 4] extinct mammals)/( [4166, 4629, 5092] mammal species - [708, 1200, 2072] endemic/island mammals) x 1/500 yrs

To calculate the relationship to the background extinction rate (BER), two more steps are necessary. First, we need to allow for uncertainty in the preservation potential, the chance that a species will be preserved. Foote (1997) estimated the preservation potential for fossil mammals as 67%, with a 99% confidence interval of 65% to 70%. Accordingly, I will use [.65, .67, .70] to represent this uncertainty.

Also, there is uncertainty in the fossil rate of mammal extinctions (in species/species million years), ranging from 0.21 (Alroy 1998) to 0.46 (Foote 1997). I will represent this as [.21, .46]. To complete the calculation of the relationship with the background extinction rate (OER/BER), then, we calculate:

OER/BER = OER X (.67 preser. poten.)/[.65, .67, .70] X 10^6 years/([.21,.46] species/species.

Doing the calculation shows that the most probable value of the observed continental mammalian extinction rate relative to background for the last half millennium is between 1.2 and 2.6 times the background rate, with a maximum range between 0 and 19 times the background continental extinction rate.

Using the same analysis for the continental birds, we obtain:

OER = [2, 3, 7]/([8705, 9672, 10639] - [1239, 1500, 2636] ) x 1/500 yrs

OER/ BER = OER X .67/[.65, .67, .70] X 10^6 years/ [.84, 1.84]

Doing the math shows the observed continental bird extinction rate is most likely between 0.4 and 0.9 times the background extinction rate, with the maximum range between 0.2 and 2.8 times the background rate.

Finally, I examined whether the Red List mammal figures would give us something radically different from the CREO figures. The CREO disqualified only five continental mammal species that appear on the Red List. Four of them were disqualified by CREO as being currently extant under a valid species name, and because of this finding by the CREO, the IUCN has referred these four species back to the relevant Red List Specialist Group for reconsideration.

If current biologists have trouble deciding if these are separate species, the chance of them being identified as separate species in the fossil record is zero. The fifth mammal, whose known range is only a single meadow, would also likely not make it into the record but might conceivably do so. This makes the fuzzy number for the Red List count of extinct continental mammals [0, 1, 5] instead of [0, 1, 4]. The effect of including the Red List mammals is to increase the possible maximum value from 19 to 23, without changing the most likely value range of 1.2 to 2.6 times background rate.

Since the results for modern extinction rates for both continental mammals and birds completely overlap the historical values, we cannot say that they are statistically different. About all we can say is that best estimate for continental mammals is between 1.2 and 2.6 times background, best estimate for continental birds is 0.4 to 0.9 times background. Neither of these seem to me to be a cause for concern.

My best to everyone,

w.

49

I don’t have access to the articles you site for your calculations, but I do know that Helen Regan, et al, [sup]1[/sup] have concluded that the “current rate of mammalian extinction lies between 17 and 377 times the background extinction rate”, which is at considerable odds with your calculations. I am unable to determine if this is the same Regan you site, as your link is dead.

One source of error in your calculations, however is the following:

You site 3 conitental mammals as having gone extinct, which is incorrect. Indeed, using the same search criteria you outlined previously for the Red List’s database, with the sole exception of not further limiting the search to forest biomes only, 27 continental mammals are shown to be extinct (or 23, if one chooses to omit “extinct in the wild”). As I am not in the habit of making idle speculations regarding the potential fossilization of modern groups (whereupon it should be further noted that “widespread” is only one of a host of factors that influence potential fossilization. We have numerous examples of species which were not particularly widespread, but by virtue of their proximity to sources of rapid sedimentation, survive in the record), I will leave it to you to adjust your calculations accordingly.

[sup]1[/sup]Helen M. Regan, Richard Lupia, Andrew N. Drinnan, and Mark A. Burgman (2001). The Currency and Tempo of Extinction. The American Naturalist, volume 157 (2001), pages 1–10

50

Darwin’s Finch, thank you for your comments. My apologies for the dead link, it’s where I got the document but that was a while ago. You have, however, identified the correct reference. It can be downloaded here (I hope). Please note that you, and Regan, and I are measuring different things.

Helen is measuring total extinctions per the Red List. I am measuring continental extinctions as certified by the CREO. You are measuring continental extinctions per the Red List, plus some island extinctions, plus extinct marine mammals, plus “extinct in the wild”.

CREO has the undertaken the task of going through all of the various claims of extinction and subjecting them to a set of standardized tests. Among these are, for example, modern DNA tests done (when possible) to see whether the animal was actually a separate species or not, and a determination if there’s even enough evidence to make a scientific decision.

If you take the list you got from the “Red List” and examine it, you will find it falls into several categories:

  1. Island dwellers. Despite leaving out the Caribbean and Pacific islands, the Red List includes a number of such island dwellers as the Swan Island Hutia, the Falklands Wolf, and a host of others.

  2. Members of still extant species. For example, the Quagga is listed by Red List as being extinct. The CREO, on the other hand, says it is “Currently extant under valid species name”, noting that “Molecular evidence (Rau, 1986; Higuchi, 1994) indicates that quagga and plains zebra are same species.” Other species, such as the Arabian Gazelle, simply do not have enough evidence at hand to determine if they were an extinct species. CREO says “Known from only two specimens, from Farasan Islands. Validity of species is in doubt (see also entry for Gazella bilkis). The gazelle that now lives on Farasan Islands is considered to be G. gazella farasani (Grubb, 1993b:396), but Groves (1985) distinguished arabica and gazella as separate species. Groves (pers. commun., 1996) considered G. arabica to be extinct (at the species level), but in the absence of additional specimens status cannot be further clarified.” I note that is was also an island dweller.

  3. Marine mammals, which I have not considered because we are looking for animals living on the continents, for E. O. Wilson’s possible victims of the cutting down of tropical forests. Examples include sea mink and Japanese sea lion.

  4. Continental dwelling mammals that are actually extinct.

Once you take out all of the first three categories, you are left with only a very few extinct continental mammals. I haven’t checked the most recent version of the list, hang on … well, there’s a surprise. The Omilteme cottontail rabbit, Sylvilagus insonus, which was listed in 2004 as being extinct, and which I listed below as one of the three extinct continental mammals, has been upgraded to Critically Endangered in the 2007 Red List. Go figure, there’s only two extinct continental mammals.

Now you and I could sit here and discuss whether there’s three, or two, or four continental mammals which have gone extinct in the last 500 years, it makes no difference. My point is simply that whatever the number is, it is so small as to be statistically indistinguishable from historical extinction rates. The idea that we are in the midst of a giant “6th wave” of extinctions is nonsense.

w.

PS - lest you think that my restrictions are too extreme, I would note that “continental dwelling mammals” as I have defined them includes about three quarters of all mammal species on the planet … note also that I have taken that fraction into account in my calculation of the extinction rates.

51

[QUOTE=intention]
There have been no continental forest birds or forest mammals which have gone extinct in the last 500 years. By “continental” I mean those birds and mammals that live and breed on the continents, not on islands (including Australia).
[/quote]

Don’t you think the following are sources of bias in your methodology?

  1. Inclusion only of continental forest extinction rates – continental extinction rates will underestimate global extinction while island extinction rates will overestimate global extinction.
  2. Exclusion of Australia – which is a continent.
  3. Exclusion of other vertebrates – amphibians and reptiles tend to be smaller and less mobile than birds and mammals, and are less likely be able to emigrate away from local extinction. (Fish vary widely in mobility.)
  4. Exclusion of invertebrates – typically even smaller and less mobile than amphibians and reptiles.
  5. Exclusion of the Carolina parakeet – which as other poster pointed out, is a forest bird.
  6. Exclusion of extinction rates in coral reefs, coastal wetlands, kelp forests, and other habitats. I disagree that “all the shouting” is about forests.

Isn’t it obvious that only extant species leave bodies? Extinct species’ bodies will have decomposed been digested (Yum!) or be awaiting discovery as fossils. :wink:

52

[QUOTE=wevets]
Don’t you think the following are sources of bias in your methodology?

  1. Inclusion only of continental forest extinction rates – continental extinction rates will underestimate global extinction while island extinction rates will overestimate global extinction.
  2. Exclusion of Australia – which is a continent.
  3. Exclusion of other vertebrates – amphibians and reptiles tend to be smaller and less mobile than birds and mammals, and are less likely be able to emigrate away from local extinction. (Fish vary widely in mobility.)
  4. Exclusion of invertebrates – typically even smaller and less mobile than amphibians and reptiles.
  5. Exclusion of the Carolina parakeet – which as other poster pointed out, is a forest bird.
  6. Exclusion of extinction rates in coral reefs, coastal wetlands, kelp forests, and other habitats. I disagree that “all the shouting” is about forests.

…

Isn’t it obvious that only extant species leave bodies? Extinct species’ bodies will have decomposed been digested (Yum!) or be awaiting discovery as fossils. :wink:
[/QUOTE]
Wevets, thank you for your thoughtful post. It is not I who have made the claim that the main issue is the decrease in the tropical forests. It was E. O. Wilson, who used the figures on tropical deforestation to get to the “6th wave of extinction” claim and to calculate the number of species going extinct, viz:

[QUOTE=E. O. Wilson]
The number of species doomed [to extinction] each year is 27,000. Each day it is 74, and each hour 3.
[/QUOTE]
You are right that a variety of other species are at risk around the world in other habitats. However, the claims of huge extinctions are not based on those locations. The “6th wave” and the 27,000 extinctions per year are supposed to be happening from deforestation.

Therefore, in order to determine the truth or falsity of Wilson’s claims, it doesn’t help us to look at all of the other options which you correctly point out above. I used birds and mammals as proxies for the other species, because birds and mammals have been studied much, much more extensively than any other groups.

If you think the Carolina Parakeet is a forest bird, you should certainly take it up with the good folks at IUCN, who maintain the “Red List”, because they don’t think so. They list 5,847 “continental” forest birds … but the Carolina Parakeet is not among them.

Finally, “where are the bodies” is my poor attempt at humor. What I meant was, where is the evidence? You will note that nobody has come up yet with a name for even one, much less a number, of the 1,000 bird and mammal species which should have already died in the “6th wave of extinction”.

w.

53

Wevets, I see upon re-reading that I did not answer your question about Australia. I wanted to exclude those places that were (and are) at risk from introduced species. These are the isolated islands along with Australia.

Think about the huge changes in Australia from the introduction of the rabbit, the fox, the domestic cat, and (thousands of years ago) the domestic dog. That’s why I left out Australia. I just went back and looked at the data, there’s 14 extinct Australian mammal species - 5 mice, a potoroo, a kangaroo, 5 wallabies, and 3 bandicoots. And where the cause of extinction is known, guess what? Dogs, cats, foxes, and humans are the culprits. A typical entry (Desert Bandicoot) says “Disappearance “coincides approximately with arrival of the fox in [this area]” (Gordon, 1995:181). Earlier disappearance in Tanami Desert may be due to changes in fire regime after end of aboriginal burning.” No mention of deforestation anywhere in the causes for extinction.

That’s why I left out Australia. Not because it is or isn’t an island, but because it has proven to be as susceptible to introduced species as the smaller chunks of land that were isolated for hundreds of thousands or millions of years. We’re looking for the “6th wave of extinctions”, not extinctions from introduced species.

w.

54

One Australian forest mammal went extinct, the Tasmanian Tiger, which was neither Tasmanian nor a tiger.

The Red List says:

[QUOTE=Red List ]
Thylacinus cynocephalus was endemic to Australia. Mainland populations are thought to have disappeared following the introduction of domestic dogs by Aboriginal human populations several thousand years ago. This restricted the Thylacine to the island of Tasmania.

The Thylacine was regarded as a threat to domestic livestock and was hunted, trapped and poisoned both for private and government bounties from around 1840 through to 1909. In addition to these hunting pressures, habitat modification, increased competition from domestic dogs and disease have all contributed to the demise of this species.

The preferred habitat of the species probably was open forest or grassland, however, the last populations may have occupied the less accessible, dense rainforest areas of southwestern Tasmania.

In 1938, the Thylacine received complete legal protection. In 1966 a 647,000 ha. game reserve was set up in southwestern Tasmania, partly to protect any animals possibly remaining in the area.
[/QUOTE]

Interesting that it radically changed habitats in response to pressure

Sounds like the Thylacine and the “domestic” dog are somehow fight-to-the-finish enemies, and that the dog is bigger or faster or works in packs or something the Thylacine couldn’t counter.

Predation by introduced species is the cause of the overwhelming majority of island and Australian extinctions. First the wild dogs of the Aboriginals, then the trained hunting dogs of the Europeans, sealed the fate of the Thylacine. A tragedy in two acts, 40,000 years apart.

w.

55

[QUOTE=intention]
Darwin’s Finch, thank you for your comments. My apologies for the dead link, it’s where I got the document but that was a while ago. You have, however, identified the correct reference. It can be downloaded here (I hope). Please note that you, and Regan, and I are measuring different things.

Helen is measuring total extinctions per the Red List. I am measuring continental extinctions as certified by the CREO. You are measuring continental extinctions per the Red List, plus some island extinctions, plus extinct marine mammals, plus “extinct in the wild”.
[/quote]

Given that the Red List was your own initial site for the number of forest extinctions, I think you are engaging in some subtle goal-post moving here. Based on your own previous cite, I am measuring the same “thing”, except not limiting my search to forests. There are many more biogeographical zones to be found on continents than just forests, and I see no good reason to exclude them if you are truly examining continental extinctions.

You will note the Red List takes the same into account. They may well reach different conclusions, but such is the nature of the beast. The intellectually honest approach would be to run the same calculations for the IUCN’s assupmtions and see whow the results differ from CREO’s.

Continental islands bear closer relationships to continents themselves than they do to oceanic islands. As such, I find your exclusion of them to be an artificial constraint.

The quagga is noted in the Red List to be taxonomically uncertain, and provisionally included until such time as its taxonomic status is resolved. Ultimately, it’s a matter of preference, depending on your particular taxonomic philosophy. Nevertheless, I would think that your “fuzzy math” is capable of accounting for such differences.

Here, I see that you are again re-defining your claim. If the claim is for continental extinctions, then ecological zone should not matter. Here, however, you are again limiting the discussion to forest biogeographical zones. So which are you actually arguing against: continental extinctions, or continental forest extinctions?

Note also that while it’s fine and well to argue against forest extinctions vs the expected losses from habitat reduction based on Wilson’s species-area relationship (and possible misapplications thereof), it should be noted that no-one in this thread has actually made any counter claims to such – you are arguing against a point no-one here has made.

And my point is that your restrictions do not argue against the larger point of current extinctions exceeding the background extinction rate. Your restrictions are too limiting to be able to compare apples to apples as you claim. The background extinction rate for mammals is an average for all mammals, regardless of biogeographical zone. As such, if one wishes to compare extinction rates, it is valid to examine the current extinctions for all mammals against the background rate for all mammals in order to draw conclusions about differences in those rates.

Rather, you are comparing extinctions in a definitially-limited class of ecological zones to Wilson’s claim about the relative number of extinctions one might expect were the relative areas of those zones to be reduced, based on the species-area relationship formula. Again, that’s fine and well, but the conclusions reached cannot be extrapolated to a wider claim of the extinction rates in general for mammals (continental or otherwise), or any other taxonomic group for that matter. And, frankly, I’m not really interested in such an argument because it really doesn’t address the fundamental question of “are species going extinct at a greater rate now than in the past?”.

It is certainly possible – indeed, likely – that extinction rates for specific biogeographical zones vary, and that therefore extinction rates for a specific zone might be greater or lower than the background rate. Unfortunately, we do not know the BER corrected for forest-only biomes, so your insistance on using forest-only biome extinctions to make conclusions about overall extinction rates is flawed from the start. Again, per Helen Regan’s paper, which you were kind enough to link: “Based on our calculations, the current rate of mammalian extinction lies between 17 and 377 times the background extinction rate measured over the past 65 million years. The best estimate of the current rate, however, falls between 36 and 78 times the background rate.” So, again, I am left with the conclusion that there is something amiss with your math or your assumptions or both.

56

[QUOTE=intention]
That’s why I left out Australia. Not because it is or isn’t an island, but because it has proven to be as susceptible to introduced species as the smaller chunks of land that were isolated for hundreds of thousands or millions of years. We’re looking for the “6th wave of extinctions”, not extinctions from introduced species.
[/quote]

If the “6th wave of extinctions” is assumed to be associated with humans, then the artificial introduction of species and any resulting extinctions is very much a part of that.

Based on your posts #52 & 53, it appears that you are, as I suspected, stuck on the “expected extinctions based on Wilson’s claims viz a viz the species area relationship vs. actual, observed extinctions”. Again, that’s a valid fight, and I fully agree that Wilson, et al have overstated the case for extinctions based on habitat loss, based on the SAR.

What I do not agree with is your subsequent dismissal of the evidence pointing to higher-than-background extinction rates. The number of mammalian extinctions, for example, over the past 500 years exceeds the expected number based on fossil extinction rates. That is a claim completely independent of Wilson and the SAR, and can be tested independently of Wilson and the SAR. And based on this claim, there is, indeed, an extinction event currently underway that warrants investigation, and yes, even cause for concern (especially if we are, as thought, even partially responsible for such).

57

Further research on the Red List reveals there are no recorded Australian forest bird extinctions.

w.

58

[QUOTE=intention]
Are you not reading what I write? Or perhaps I am not being clear. I had specified continental mammals and birds, and specifically excluded Australia and islands.
[/quote]

No, you didn’t. You said that you were referring to animals of the continents, including Australia. Your sloppy grammar has confused you.

But one has to ask why you have arbitarily decided to exclude Australia, which is the continent to mopst recently see the introduction of agriculture. Could it be that you have deliberately rigged the criteria so that prehistoric extinctiosn that can’t be definiteively attributed to habitat loss are excluded? It sure seems that way.

So what? You said that no bird has become extionct. That bird is extinct. I couldn’t give shit whether it is is or isn’t on one list or another. All I care about is whether it is or is not extinct. Are you disputing that it is extinct?

I see, to we keep moving the goalposts until we get the answer we want. Kinda hard to lose an arument that waty, but also kinda hard to cinvince an intelligent audience.

There is no evidence that dogs hunted thylacines without human enticement. Moreover you said that no continental forest mammal had become extinct for any reason. This was a continental mammal of the forests. It is extinct. You are wrong.

Dude I just made list of species that have become extinct due to habitat destruction. Why do you insist on ignoring it?

Is that all you want? That’s easy.
Centropus colossus, Megalibgwilia ramsayi

59

[QUOTE=intention]

Instead, we have to ask ourselves a slightly different question - what would an archaeologist a million years from now calculate as the extinction rate (for continental birds or mammals) for our time?
[/QUOTE]

I may not be a cowboy, but I know when someone’s trying to sell fertilizer instead of prime beef. :wink:
It’s not that your math is wrong (I haven’t checked it,) it’s that you start from flawed premises.

60

… am I just being trolled? … I hope not …

Blake, rather than restate the entire story every time, I stated it at the start. However, since you seem to have missed that part, here it is, the original statement:

Seems pretty clear to me. Which part of ‘on the continents, but excluding Australia and islands’ didn’t you understand?

But if you are so eager to include Australia, fine. I will say that there have been no recorded extinctions of forest birds and mammals that live and breed on the continents (excluding Australia and islands) in the last 500 years. Which is what I said before.

I will also say that in five hundred years there has only been one forest bird or mammal which has gone extinct in Australia, and it was driven to extinction by introduced species (dogs and humans).

Can we now get back to the subject of the thread, the fabled sixth wave of extinction?

w.

PS - I asked for names of species suffering recent extinctions from E. O. Wilsons fabled “6th wave”. You give me, not a species going extinct in modern times from current deforestation, and not a denizen of the Red List, which looks at the extinctions of the past five centuries.

You give me a fossil bird from thousands of years ago … are we speaking the same language? What part of 'in the last 500 years" are you not getting here?

PPS - I did not ignore your list of aurochs and Himalayan quail and the like as you accuse me of doing. I answered right away and discussed each case. And I told you that if you don’t like the fact that the aurochs is not considered an extinct species by the scientists, you should take it up with the scientists. Why are aurochs back on the agenda? Or did you post some other list that I don’t know about? What am I missing here?