Where Are The Corpses?

Guest Post by Willis Eschenbach


The record of continental (as opposed to island) bird and mammal extinctions in the last five centuries was analyzed to determine if the “species-area” relationship actually works to predict extinctions. Very few continental birds or mammals are recorded as having gone extinct, and none have gone extinct from habitat reduction alone. No continental forest bird or mammal is recorded as having gone extinct from any cause. Since the species-area relationship predicts that there should have been a very large number of recorded bird and mammal extinctions from habitat reduction over the last half millennium, I show that the species-area relationship gives erroneous answers to the question of extinction rates.

Figure 1. The Object of My Quest — The Corpse of an Extinct Bird


A recent study in Nature [Thomas 2004] stated that 37% of all species might soon go extinct because of habitat reduction due to global warming. This same prediction of impending mass extinctions from habitat reduction due to global warming has been made a number of times recently, for example in a book by Professor Michael Benton of Bristol University (Benton 2003), as well as in studies by Parmesan and Yohe (Parmesan 2003) and Root et al. (Root 2003).

Habitat reduction has also been cited as being responsible for the continuing extinction of species which is said to have already happened due to the cutting down and fragmentation of tropical forests (Wilson 1995, 2001). For example, a recent study in Conservation Biology (Harris 2004) opens by saying that “Intense deforestation causes massive species losses.” Wilson says that due to habitat reduction we are in the “sixth great wave of extinctions”, comparable in size to the five previous great waves of extinctions in geological time. (Wilson 1992).

Reading these kinds of claims over and over again made me think, “Well, if there’s been all of those claimed extinctions of birds and mammals … where are all the corpses? What are the names of all the extinct birds and mammals”? This research paper investigates these claims that habitat reduction from temperature change and deforestation has led and will continue to lead to the extinction of a large number of species.

A few clarifications are in order.

This study is not about estimated, predicted, or calculated extinctions. It is an analysis of the actual historical record of extinctions, with the purpose of understanding the nature and size of extinctions from historical habitat reduction.

By extinction I never mean local extinction. I have analyzed total extinctions of species (not subspecies). Local extinction is a separate and valuable study, not covered by this work.

I am not referring to “almost extinct,” “on the brink of extinction,” or “reportedly extinct.” I am discussing the actual extinction of species as confirmed by the relevant authorities.


In their seminal work, “The Theory of Island Biogeography”, Macarthur and Wilson further explored the “species-area” relationship (Macarthur 1963). This relationship, first stated mathematically by Arrhenius in 1920, relates the number of species found to the area surveyed as a power law of the form S = C * a ^ z , where “S” is species count, “C” is a constant, “a” is habitat area, and “z” is the power variable (typically .15 to .3 for forests). In other words, the number of species found in a given area is seen to increase as some power of the area examined.

By surveys both on and off islands, this relationship has been generally verified. It also passes the reasonability test — for example, we would expect to find more species in a state than we find in any one county in that state.

Does this species-area relationship work in reverse? That is to say, if the area of a forest is reduced, does the number of species in the forest decrease as well? And in particular, does this predicted reduction in species represent species actually going extinct? One of the authors of “Island Biogeography” thinks so. In 1992, E. O. Wilson wrote that because of the 1% annual area loss of forest habitat worldwide, using what he called “maximally optimistic” species/ area calculations, “The number of species doomed [to extinction] each year is 27,000. Each day it is 74, and each hour 3.” (Wilson 1992).

If we have lost 27,000 species per year since 1992, that’s over 300,000 species gone extinct. In addition, Wilson said that this rate of forest loss had been going on since 1980, so that gives us a claim of over well over half a million species lost forever in 24 years, a very large number.

Wilson also wrote, “Some groups, like the larger birds and mammals, are more susceptible to extinction than most.” (Wilson 1995) So, following Wilson’s lead to see if the extinction claims are true, I have investigated the timing and number of mammal and bird extinctions in modern times (the last 500 years) which are due to habitat reduction.

There are many different estimates of species loss, varying by orders of magnitude. I have seen extinction claims as high as “one species per minute” (over half a million extinctions per year, 10 million species extinct in 20 years) quoted in a number of places. However, I wanted facts, not estimates.

There are two main lists used by scientists to keep track of the facts of extinction. One is the “Red List”, maintained by the International Union for Conservation of Nature and Natural Resources (IUCN), which lists species which are either extinct or at risk of extinction. The Red List database can be searched online at redlist.org.

The other is the CREO list, from the Committee on Recently Extinct Organisms at the American Museum of Natural History. Their database is online at creo.amnh.org. The CREO has established very clear criteria for declaring a species extinct, not extinct, or unresolved. The criteria include precise definitions for such things as adequate taxonomy (including DNA comparisons if available), sufficient hypodigm (actual specimens of the species), and adequate surveying of the species’ habitat to verify extinction. Starting afresh, they have then uniformly applied these criteria to the historical record of purported extinctions of mammals and fish in the last 500 years.

The conclusions of the CREO list are noted in the Red List, and vice versa. Although the two lists are very similar, I find the CREO list to be more thoroughly investigated and more uniformly and scientifically based than the Red List, so I have used it for mammal extinctions (it does not yet cover birds).

Timing and Size of the Extinctions

The bulk of the extinctions took place in several waves, as Europeans expanded outwards in successive centuries. Island after island has seen specialized native species driven extinct by imported species. These invader driven extinctions peaked in about 1900, but are still going on.

Figure 2 – 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.

Figure 2 shows see the complete record of every known bird and mammal extinction. In general, the timing reflects the various phases of the expansion of a variety of European species, including humans. Starting from the Caribbean extinctions in the 1500’s, extinctions continue through the age of exploration in the 1700’s and the colonial period of the 1800s. This wave of “alien species” extinctions peaked around 1900 at 1.6 extinctions per year. Extinction rates have dropped since then, with the most recent value being 0.2 extinctions per year.

Wilson’s claim that 27,000 extinctions per year have been occurring since at least 1980 means that there should be 26 bird extinctions and 13 mammal extinctions per year, a total of 39 bird and mammal extinctions per year.

The historical extinction rate, however, has never been greater than 1.8 per year, far below the 39 extinctions per year claimed. In addition, the most recent rate is lower than it has been since about 1830. Looking at the entire bird and mammal extinction record, there is no sign of the hundreds of extinctions that Wilson says have already occurred.

I was not interested, however, in all of the mammal and bird extinctions. In particular, I was not interested in mammals and birds that had gone extinct on islands from the introduction of alien species. I was looking for Wilson’s predicted extinctions, those due to habitat reduction.

So I divided all of the extinctions into two groups. The first group is the extinction of those species living on isolated islands or on Australia, where species were (and still are) easily driven to extinction by the depredations of imported dogs, foxes, mongoose, rats, human hunters, goats, pigs, snails, cats, sparrows, frogs, starlings, and various plants, as well as the usual assortment of imported human, animal, and plant diseases. I will call this group of extinctions “island” extinctions. Please don’t write to tell me Australia is not an island. It is grouped with the islands because of the nature of the extinctions there, which were caused by imported alien species.

The second group is the extinction of the continental species, the mass of the world’s species, those species that live on the continents (Asia, Europe, Africa, North America, South America, and Antarctica.) I will call this group “continental” extinctions.

It is not widely appreciated how much island extinctions have dominated the total record of extinctions. Here are the extinct mammal species, showing island extinctions and continental extinctions:

Count of Extinct Mammal Species

Island vs. Continental                      Country   Total

Extinct Island Mammal Species            Various       58

Extinct Continental Mammal Species     Mexico       1

Extinct Continental Mammal Species   Algeria          1

Extinct Continental Mammal Species South Africa  1

Extinct Continental Mammal Species    Subtotal       3

Grand Total Extinct Mammal Species                          61

Data – http://creo.amnh.org

Of the 4,428 known mammal species (Red List 2004) living in Asia, Europe, Africa, North America, South America, and Antarctica, only three mammals have gone extinct in the last 500 years. These were the Bluebuck antelope, South Africa; the Algerian gazelle, Algeria; and the Omilteme cottontail rabbit, Mexico.

Turning next to birds, when we are studying the extinction of species, birds have a very useful trait — they are extremely visible. Nearly all of them fly up where we can see them; they make distinct and identifiable noises; many are brightly colored; none are too small to see; many roost in trees so they can be seen from afar with binoculars; in all, they are perhaps the most visible of all classes of life. Because of this, they are well-known to humans everywhere — all 129 extinct birds have a common name, for example, which is not the case with other classes of animals. Based on where the birds breed, here’s how the data from the Red List divides out between continental and island bird extinctions:

Count of Extinct Bird Species

Island vs. Continental                      Country   Total

Extinct Island Bird Species              Various     123

Extinct Continental Bird Species    Mexico          1

Extinct Continental Bird Species  Guatemala     1

Extinct Continental Bird Species   Colombia       1

Extinct Continental Bird Species      US                 2

Extinct Continental Bird Species  Canada, US    1

Extinct Continental Bird Species Total                  6

Grand Total Extinct Bird Species                         129

Data – http://www.redlist.org

We see the same pattern with birds as with mammals. Of the 128 extinct bird species, 122 of them were island extinctions. Of the 8,971 known continental bird species (Red List 2004), 6 have gone extinct.

Looking at the reasons for the continental bird and mammal extinctions, in chronological order we have:

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. (CREO)

Carolina Parakeet, Conuropsis carolinensis, 1904 – Hunted for food and for the millinery trade, killed for crop protection and because it competed with bees. Also said to be affected by deforestation. (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, Ectopistes migratorius, 1914 – “… Newcastle disease, extensive hunting, and the breakdown of social facilitation”, plus a reduction in food supply (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 (found only on Lake Atitlan, Guatemala) – “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)

What can we conclude from this record of extinctions?

1)  When European species met isolated local species, a number of the local species died. The Australian and island species were extremely vulnerable to pressure from imported humans, mammals, birds, plants, and diseases. 95% of all recorded bird and mammal extinctions are island or Australian species.

2)  When the European species arrived, Australia and most islands had been separated from the continents for forty million years or so. The initial introduction of European species into island habitats was a one-time event. While alien species will always a problem for islands, this massive onslaught of the first coming of the European species will never be repeated — there are no places left with forty million years of isolation.

3)   Total habitat destruction drove one bird to extinction.

4)  While habitat reduction has been claimed as contributing (in an unknown degree) to three continental bird extinctions, to date no continental mammal or bird has been seen to go extinct due to habitat reduction alone.

Three continental mammals have gone extinct — one antelope hunted to extinction, and a rare rabbit and a rarer antelope gone from unknown causes.

Six continental birds have gone extinct — 3 prolific terrestrial bird species hunted to extinction, and 3 single-habitat freshwater bird species hunted, drained dry, eaten by fish, and polluted to extinction.

This historical record of 9 continental extinctions in 500 years contrasts starkly with Wilson’s predictions of over thirty continental bird and mammal extinctions per year, each and every year. Even if his numbers were off by an order of magnitude, we should be seeing more than 3 continental extinctions per year from habitat reduction since at least 1900, which totals around 300 continental extinctions. We simply have not seen those extinctions, in fact there’s only 9 continental extinctions in the 500 year record.

Finally, let us examine Wilson’s claim that due to forest habitat reduction, “The number of species doomed each year is 27,000.” (Wilson 1992)

Bird species make up about .1% of all species, and mammal species are about .05% of all species (IUCN 2000). Using Wilson’s figure of 10 million total species, he is claiming about 16 continental bird extinctions (27,000 species doomed times 8,433 continental bird species per 10,000,000 species) and 11 continental mammal extinctions (27,000 species doomed times 3,921 continental mammal species per 10,000,000 species) per year, for a total of 34 predicted continental bird and mammal extinctions per year. (I have used Wilson’s figure of 10 million species on earth, although modern estimates vary. Using Wilson’s figure allows the total number of species to cancel out in the calculation.)

In 1988, Wilson said that a 40% reduction in forest habitats had already occurred (Wilson 1988). Using Wilson’s “maximally optimistic” z value of .15 and his 1% annual forest loss, with 40% habitat reduction in 1988, the total species loss to up to 1998 should be 1,088 continental bird and mammal extinctions. Over a thousand continental bird and mammal extinctions predicted, and not one of them shows up in the record.

Wilson’s Explanations of the Discrepancy

Professor Wilson has offered two explanations for the discrepancy between his predictions of massive extinctions and the lack of corresponding extinctions in the historical record. His explanations are:

1)  That it is not known whether species have gone extinct recently, as species cannot be declared extinct for 50 years.

2)  That the species do not go extinct immediately, but can take up to 100 years to die out.

Regarding the first explanation, Wilson has written: “To declare a species officially extinct, not only does a species have to be known to science and absent from captive populations, but the World Conservation Union (IUCN) demands that the ‘species (is) not definitely located in the wild during the last 50 years’ (Collar et al. 1992, p. 1025). This is an extremely conservative criterion, particularly when indirect evidence strongly indicates that extinction rates are accelerating.” (Wilson 2001)

However, this 50 year criterion is not used by the IUCN, nor by CREO. For example, as quoted above, the IUCN Red List 2000 showed the last Atitlan Grebe dying in 1986. The data source for the listing is “BirdLife International. 2000. Threatened Birds of the World. Lynx Editions”. This means that the species was declared extinct by the IUCN only 14 years after the last Atitlan Grebe died. And the CREO lists the most recent mammal extinction as occurring in 1991, only a nine-year lag.

If Wilson’s criteria were used, there could be no extinctions in the IUCN Red List 2000 where the species was last recorded later than 1950. But in fact, there are 10 birds and 5 mammals in the Red List 2000 that were last recorded after 1950. Thus Wilson’s first explanation is not correct.

Professor Wilson’s other explanation for the lack of predicted extinctions is that they do not happen at once. He says that the “species in a reduced habitat may take from 25 to 100 years to go extinct”, and that research has shown that the rate of these delayed extinctions drops off exponentially with time (Wilson 2001). While this seems plausible, even if it were true it wouldn’t keep us from seeing the predicted extinctions.

We can see why by applying the exponential die-off to the 1,088 bird and mammal extinctions said to have occurred by 1998. Let’s assume all 1,088 of them fatally lost habitat at some point since 1948, but they won’t die out for 100 years. 1,088 species lost in 50 years (1948-1998), that works out to 21.76 per year, about 22 species “doomed to extinction” each year since 1948.

With exponential decay, to still have one species of 100 left alive after 100 years, the exponent needs to be 1 – (1/100)^(1/100), or .045. This means that 4.5% of the remaining doomed species should go extinct each year.

But if we had doomed 22 bird and mammal species to extinction every year since 1948, and only 4.5% of the doomed species went extinct each year, then by 1960, of the 261 predicted eventual bird and mammal extinctions, we should have seen 65 extinctions. By 1980, of 696 predicted eventual extinctions, we should have seen 340. And by the year 1998, of the 1,088 extinctions predicted by species-area calculations, we should have seen 672 actual extinctions of continental birds and mammals.

We have seen none. Even if Wilson’s predictions were off by an order of magnitude, we still should have seen 67 extinctions from habitat reduction since 1948. We have seen none.

Pimm et. al. (Pimm 1995) argues that extinctions in eastern North America support the species-area relationship. His findings are marred by several inconvenient facts. First, according to the Red List, two of the four extinct species he cites (Ivory Billed Woodpecker and Bachman’s Warbler) are not listed as extinct.

Second, the other two species (Passenger Pigeon and the Carolina Parakeet) were not just eastern forest dwellers, but ranged widely over both forest and fields. Birdlife International says of the Carolina Parakeet “Birds were wide-ranging but their typical habitat was cypress and sycamore trees along rivers and swamps.” It describes the Passenger Pigeon’s habitat as ” Ectopistes migratorius was found in forest in eastern and central Canada and the USA, occasionally wandering south to Mexico and Cuba.”

Third, and most important, both the Carolina Parakeet and the Passenger Pigeon were extensively hunted. The Passenger Pigeon in particular was subjected to what was possibly the most concentrated hunting of any known bird. The Carolina Parakeet, the only North American parakeet, was hunted for its valuable bright feathers. No bird species could survive that type of intense hunting. Claiming that these extinctions were caused by habitat loss ignores the main cause, hunting.

The Atlantic Coastal Forest records also contradict Pimm’s claims. The cutting of the Atlantic Coastal Forest in Brazil has been going on for decades, with over half of the forest cut down by 1960 (Mendonça, 1994), and only 10% of the forest currently remaining (Harris, 2004). There are 179 endemic bird species in the forest, according to Pimm and Harris (Harris, 2004). From this 90% deforestation, the species-area relationship predicts 52 bird species doomed to extinction. Including the 100-year exponential decay, we should have already seen some 25 birds go extinct in the Atlantic Coastal Forest, with 27 more to come. In fact, no birds from the Atlantic Coastal Forest are recorded as having gone extinct, and only one bird (Alagoas Curassow) from the Atlantic Coastal Forest is extinct in the wild. (The fate of the Alagoas Curassow is not surprising, and once again is not related to habitat but to hunting. Because it is a very large bird, almost a metre tall, and has always been heavily hunted for food, Birdlife International says, “The extinction of this species was forecast almost as long ago as its discovery”. And that’s been a while, as Linnaeus first scientifically described it in 1740.)

Harris and Pimm (Harris, 2004) further argue that the species-area relationship predictions for the Atlantic Coastal Forest are validated by the fact that a number of birds of the forest are threatened with extinction, but this is a circular argument – many of these birds are listed as threatened with extinction solely because of reduced habitat.

While scientists might have missed a few of the predicted extinctions, the odds of them missing every one of these hundreds of claimed extinctions are nonexistent. These are birds and mammals, the most studied and best-known classes of animals on earth. Yet after all of the habitat reduction in all continents in 500 years, we have only seen 9 continental mammal or bird extinctions. There is no sign of the hundreds of bird and mammal extinctions predicted by the species-area relationship.

Red List Birds

Wilson says his estimates are supported by “The velocity of passage of species through the categories in the World Conservation Union (IUCN) Red List of Threatened Species, from less endangered to extinct.” (Wilson 2001)

This claim creates an image of thirty birds or so moving a step towards extinction each year. But this is not the case for two reasons — the change in the count of birds at risk is far too small for this to be true, and the number of birds in the highest risk category (Critically Endangered) has actually decreased. Figure 3 shows the velocity of passage of all bird species through the Red List from 2000 to 2004. There is no significant change in the numbers of birds in any category.

Figure 3. Red List Birds By Category, 2000-2004. None of the categories have changed significantly since the first records in 2000. Vulnerable and Endangered birds have increased slightly, although part of this may be because habitat reduction is incorrectly considered as a major threat. Extinctions are unchanged at 129. Extinct in the Wild increased by 1. The number of Critically Endangered birds has decreased by 3 since 2000, one bird moving towards extinction and two birds moving away from extinction.

Forest Bird and Mammal Extinctions

Finally, here is what I consider the most surprising fact to emerge from my research. In all the continents, we have never seen a single forest bird or mammal go extinct from any cause whatsoever. None of the nine extinct continental birds and animals was a forest dweller.

This unexpected lack of continental forest bird and mammal extinctions can easily be verified by searching the online Red List. Go to http://www.redlist.org/search/search-expert.php?kingname=ANIMALIA&phyname=CHORDATA&claname=AVES. Select “Forest” as the habitat, “Extinct” as the category, and all areas of the world except Oceania and the Caribbean as the location. The search will reveal only three Hawaiian island forest birds. The same search can be done for mammals (replace AVES in the URL with MAMMALIA), and reveals the same pattern – the only extinctions listed are five island forest bats. In all of the continental forests of the world, here has never been a single recorded bird or mammal extinction.

This lack of even one continental forest bird or mammal extinction, in a record encompassing 500 years of massive cutting, burning, harvesting, inundating, clearing, and general widespread destruction and fragmentation of forests on all of the continents of the world, provides a final and clear proof that the species-area relationship simply does not work to predict extinctions.

Summary of Methods

Reliance on the species-area relationship’s predictions of extinctions is an accepted tenet of the biological and ecological sciences. I, on the other hand, say it doesn’t work. Extraordinary claims require extraordinary evidence.

I have therefore presented four separate lines of evidence establishing the failure of the species-area relationship to predict extinctions:

1)  Current Overall Extinction Rates — The most recent total bird and mammal extinction rate in all parts of the world, both islands and continents, is about 0.2 extinctions per year (see Fig. 1). This is down from a peak of about 1.6 extinctions per year a century ago. There is no sign of the nearly 40 bird and mammal extinctions per year predicted by the species-area relationship. Nor is there a rise in the rates — in fact, they have generally fallen for the last hundred years, while habitat destruction has increased during that time. Wilson, using the species-area relationship, claims the extinction rates are 200 times higher than what the data actually shows. (In reality, his claim that extinction rates are 200 times higher than what the data shows is the extraordinary claim requiring extraordinary proof.)

2)  Total Continental Extinctions — None of the nine recorded continental bird and mammal extinctions were from habitat reduction. But no matter the reason for their extinction, the total number of extinctions is way too small. Nine continental bird and mammal extinctions in 500 years is a very, very long way from the thousand plus continental bird and mammal extinctions predicted on the basis of the species-area relationship.

3)  Birds on the Red List — There has been no significant change in the numbers of birds in the highest risk categories of the Red List in the four years since its creation.

4)  Forest Extinctions — There are no recorded continental forest bird or mammal extinctions from any cause. The species-area relationship says we should have seen hundreds and hundreds of forest bird and mammal extinctions from worldwide forest habitat reductions. We have seen no forest extinctions from any cause.

Each of these independent lines of evidence shows that the species-area relationship does not work, that the relationship predicts a large number of extinctions from habitat reduction while the data shows no extinctions from that cause. I have also examined Wilson’s two explanations for this discrepancy, and I have shown that neither of them explains the lack of extinctions.

All of the conclusions drawn by these lines of evidence are very robust; in fact, they are all immune to a variation of an order of magnitude in the assumptions. That is to say, even if the predicted extinctions were only a tenth of what the species-area relationship actually predicts, the conclusion still stands in each case, that the species-area relationship gives incorrect predictions. And in particular, the total absence of continental forest extinctions in the 500-year record provides a final and absolute proof that the species-area relationship does not work to predict extinctions.


I am concerned that this study will be mis-used to justify cutting any forest any time. Let me make clear what this study does not say.

None of this implies that habitat destruction, forest fragmentation, or loss of species diversity are incidental or unimportant issues.

The contrary is true. Diversity is vital to ecosystems; the more types of life in an ecosystem, the better the ecosystem works. Local extinctions can have large negative effects on the local area. Clear-cutting forests for agriculture can change the local climate. Cutting forests recklessly can drive fish species extinct through siltation. Nothing in this study detracts from the need to provide reserves and parks and wildlife areas. In short, allowing for other species in our plans is essential.

None of this implies that extinctions will either rise or fall in the future.

This is an analysis of the historical record to date.

And finally, none of this implies that habitat destruction has no effect on the risk of extinction.

It clearly can and does have an effect; but the effect of habitat reduction appears to be too small to cause extinction by itself. In addition, habitat reduction appears to be mathematically unrelated to the extinction rate, and in particular the relationship is not represented by the species-area equation.

Extinction records do show that on all the continents of the world, there are no recorded cases of a forest bird or mammal that has gone extinct from any cause. This is despite the fact that humans have been reducing and fragmenting all natural habitats, including first the continental temperate forests and lately the continental tropical forests, for the 500 years covered by our extinction record. Five hundred years ago, reduced (fragmented) forest habitats were the exception. Fragmented forests are now the rule, about half the original forest worldwide is gone, and some places like the Brazilian Atlantic Coastal Forest and some “biodiversity hot spots” have lost 75% to 90% of their forests.

If the species-area relationship were correct in predicting extinctions, over these 500 years of forest (and other habitat) reduction, surely we would have seen at least a few dozen of the hundreds of predicted bird and mammal extinctions from this putative cause. But to date, no continental forest bird or mammal has ever gone extinct from any cause.

Given these four separate lines of evidence, I can only conclude that while the species-area relationship works well as a predictive tool for determining the number of species to be found by a survey, it fails completely when used to predict extinctions of continental bird and mammal species consequent to habitat reduction.

Possible Explanations

I don’t know why the species-area relationship doesn’t work to predict extinctions. I would have guessed it would work — it seems so reasonable. I do have some thoughts, however:

1.  One possibility is that it does work, but that the “z” factor for extinctions is much, much smaller than the z factor for counting species in an area. After all, speciation and extinction are radically different processes — why should they have the same z factor? However, the lack of even one recorded continental forest extinction argues strongly against this explanation, because with half the world forest gone with no extinctions, the “z” factor would have to be so small as to be meaningless.

Another possibility is that the exponential die-off could be very slow. Brooks et. al., for example, say it is on the order of 330 years to reach 1% (which is a 50 year half-life) (Brooks 1995). But if the die-off were over 1,000 years, rather than the shorter times stated by Wilson or Brooks, we still should have already seen 118 bird and mammal extinctions from the predicted 1088 “doomed” continental bird and mammal species. Even if the decay were 5,000 years, we still would have seen 25 extinctions from habitat reduction. In fact, we have seen none — so long die-off times cannot be the reason why the species-area relationship does not work.

2.  The total lack of any data to corroborate the use of the species-area relationship to predict extinctions makes it very difficult to explain why the species-area relationship does not work. If it worked but gave answers that were usually too high or too low compared to the data, it would be possible to test various scenarios. However, with no recorded extinctions from habitat reduction, this is not possible.

3.  In the 500-year period covered by the record of extinctions, forest habitat reduction has not completely destroyed any known continental bird or mammal species’ total possible habitat. If it had done so, we would most likely have seen the resulting extinction in the record — extinction from total habitat destruction is a possibility for any species, as happened to the Slender-billed Grackle.

4.  However, given the amount of forests destroyed worldwide, the odds are very good that we have completely destroyed a number of known species original habitats.

5.  This means that, although a species’ original habitat may be totally destroyed, under extreme external pressure it may successfully move to another habitat.

6.  Forests are not cleared instantaneously. They are cleared over a period of years or decades, with nearby stands falling first and then more distant stands at a later date. This gives species time to move.

7.  Species are incredibly adaptive and tenacious. Under pressure, many species are able to adapt to the changed circumstances by changing their preferred food, nesting sites, or other behaviors.

8.  Evolution is alive and well, and can operate in human time (centuries rather than millennia) (Badyaev 2002, Pergams 2003). This implies that species may actually be evolving, as well as migrating, adapting, and changing, to keep from going extinct.

9.  The one common thread of almost all recorded bird and mammal extinctions, both island and continental, is that one species actively goes out and hunts another species to extinction. Foxes, cats, mongoose, humans, rats, Newcastle disease, brown tree snakes, all of these species and more have actively driven other species to extinction. Absent hunting, very few species have ever gone extinct.

In short, this all suggests that the answer to the question of why the species-area relationship doesn’t work for birds and mammals is that they inconveniently refuse to die unless they are hunted down and killed one by one until the last one is gone. The species-area relationship doesn’t work because life, once created, struggles endlessly to survive. Life breaks rules to survive, cuts bonds, crosses gaps, jumps barriers, changes habitats, life does anything to survive.

The species-area relationship doesn’t work to predict extinctions because if you cut down half a forest, every single one of the resident bird and mammal species moves into the other half of the forest. They don’t know that they’re supposed to go extinct, no one told them, and so they do whatever they need to do to survive. And as the evidence shows, in fact they do make the move and they do survive — remember, despite massive forest habitat reduction, no continental forest bird or mammal has been recorded as going extinct in 500 years. No matter how the forest was cut, chopped, burned, and mangled, every one of the forest birds and mammals has somehow managed to survive — and that’s why the species-area relationship doesn’t work.

New or Modified Theories Relating Habitat Area and Extinction

10.  At present, no theory attempting to mathematically relate habitat reduction to bird and mammal extinction can be tested because of the record – no continental bird or mammal has ever been recorded as going extinct from habitat reduction alone, and no continental forest bird or mammal has ever been recorded as going extinct from any cause.

11.  Any new theory attempting to relate extinctions and habitat area must first correctly predict the past. It must first predict 500 years without a single continental forest bird or mammal extinction, during five centuries of massive historical forest habitat reductions on all continents, before looking to predict the course of future extinctions.

12.  Although habitat reduction clearly can pose a threat to any species, the nature and size of that threat is not mathematically related to the amount of habitat reduction involved. Otherwise, we would have seen forest bird and mammal extinctions.

Final Implications

13.  Based on the 500-year historical record, there is only a weak relationship between habitat reduction and bird or mammal extinctions. Unlike real extinction threats like predation by humans or other species, habitat reduction has played only a minor part in extinction.

14.  Accordingly, habitat reduction should be downgraded severely in the Red List of threats of extinction. At present, it is in first place on the List, giving a false impression of importance.

15.  The use of habitat reduction as a large factor in determining the danger of extinction is a circular argument, creating “evidence” that seems to support the species-area relationship (more Red List species considered to be in danger of extinction because of habitat reduction). However, that “evidence” derives from assuming the species-area relationship works, and thus can’t be used as “proof” that the relationship works.

In other words, if the criteria for inclusion on the Red List include the species-area relationship idea of habitat reduction as a major extinction threat, the number of birds on the Red List cannot be used to determine whether the species-area relationship works. Only actual extinctions can do that — and looking at actual extinctions there is no evidence that the species-area relationship works at all to predict extinctions.

16.  The listing of “habitat reduction” as a factor in extinctions is also suspect because habitat reduction is so common. At present, the majority of all bird and mammal species have a reduced habitat compared with 500 years ago, so “habitat reduction” could be cited for nearly any extinction. Generally, it seems to be a secondary factor, one that only comes into play when combined with a major factor such as hunting or poisoning.

17.  The 500-year record includes the so-called “Little Ice Age” of the 1600 and 1700’s, when global temperatures were much lower than today. Claims that small climate changes can cause widespread extinction are thus discredited in two ways: one is that they rely on the species-area relationship; and the other is that the historical record shows no sign of these extinctions from small climate changes.

18.  One or two or even a dozen missed bird or mammal extinctions would not change these conclusions at all, as the predicted extinctions are far too numerous to be challenged by such a small number.

19.  Removing the idea of habitat reduction as a major extinction threat will allow us to focus on the real main modern extinction threat, that of invasive, predatory alien species, in particular humans.

For example, it is not the cutting of the African forests that is the main danger to the species living in the forests — it is the bushmeat trade, and the poaching for furs and body parts, which are putting species at risk. Hunting, both by humans and by invasive species, may well yet drive a number of species to extinction. This is the real extinction threat of the 21st century, the threat that we should be working to counter.

Finally, please don’t bother disputing this or that individual record of extinction. Yes, I realize that the Ivory Billed Woodpecker is likely extinct, despite what the official lists say. And I originally wrote this in 2005, so maybe another bird or mammal has gone extinct since then. But changing the status of one or a few birds or mammals makes no difference to my thesis. We are looking for dozens and dozens of missing corpses, not one or a few.

Literature Cited

Badyaev, A. V., Hill, G. E., 2002, Avian quick-change artists: exemplars of rapid adaptation, house finches show that mothers know best. Natural History, June, 2002, http://www.findarticles.com/cf_dls/m1134/5_111/86684504/p1/article.jhtml?term=

Benton, M, Thames & Hudson, When Life Nearly Died, May 2003 ISBN: 050005116X

Brooks, T. M., Pimm, S. L., Oyugi, J. O., 1995, Time Lag between Deforestation and Bird Extinction in Tropical Forest Fragments, Conservation Biology, Pages 1140–1150, Volume 13, No. 5, October 1999

CREO, 2000, Continental mammal extinctions from the Red List that were  disqualified by CREO, with the reason for disqualification:

Extant under valid species name, Cervus schomburgki, Schomburgk’s deer

Extant under valid species name, Gazella bilkis, Queen of Sheba’s gazelle

Extant under valid species name, Gazella arabica, Arabian gazelle

Extant under valid species name, Equidae, Equus quagga, Quagga

Harris, G. M., Pimm, S. L.,  2004, Bird Species’ Tolerance of Secondary Forest Habitats and Its Effects on Extinction, Conservation Biology Volume 18 Issue 6 Page 1607  – December

IUCN, 2000, All data regarding total numbers of bird and mammal species are from the IUCN, available as a PDF file at http://www.wri.org/wr-00-01/pdf/bi2n_2000.pdf. IUCN extinction data are from the IUCN Red List 2000, at http://www.redlist.org. Selected data from the 2002 Red List are available at http://www.birdlife.net/datazone/downloads/index.html.

MacArthur, R. H., Wilson, E. O., 1963, The Theory of Island Biogeography,  ISBN: 0-691-08836-5

Mendonça, J. R., de Carvalho, A. M. Mattos Silva, L. A. and Thomas, W. W.  1994.  45 Anos de Desmatamento no Sul da Bahia, Remanescentes da Mata Atlântica – 1945, 1960, 1974, 1990.  Projeto Mata Atlântica Nordeste, CEPEC, Ilhéus, Bahia, Brazil.

Parmesan, C. and Yohe, G.  2003.  A globally coherent fingerprint of climate change impacts across natural systems.  Nature 421: 37-42

Pergams, O. R. W., Barnes, W. M., and Nyberg, D., 2003, Rapid change of mouse mitochondrial DNA. Nature 423:397, http://home.comcast.net/~oliver.pergams/Nature.pdf

Pimm, S. L., Askins, R.A., 2005, Forest losses predict bird extinctions in Eastern North America, Proc. Natl. Acad. Sci., Vol. 92, PP 9343-9347, September 1995

Root, T.L., Price, J.T., Hall, K.R., Schneider, S.H., Rosenzweig, C. and Pounds, J.A.,  2003,  Fingerprints of global warming on wild animals and plants.  Nature 421: 57-60]

Wilson, E. O., 1988, Biodiversity, National Academy of Sciences

Wilson, E. O., 1992, The Diversity of Life Harvard University Press, Cambridge, MA.

Wilson, E. O., 1995 Only Humans Can Halt the Worst Wave of Extinction Since the Dinosaurs Died  http://raysweb.net/specialplaces/pages/wilson.html

Wilson, E. O., 2001, Vanishing Point – On Bjorn Lomborg and Extinction, Grist, 12 Dec http://www.gristmagazine.com/grist/books/wilson121201.asp

Wilson, E. O., Perlman, D. L., 2000, Conserving Earth’s Biodiversity, Island Press, 2000


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not dead but scared off…

‘Scarecrow’ wind farms put rare birds to flight
Britain’s upland birds are in danger of being driven off hills and mountains by onshore wind farms.
Scientists have found that birds, including buzzards, golden plovers, curlews and red grouse, are abandoning countryside around wind farms because the turbines act as giant scarecrows, frightening them away.

but not a word on where they are going though…

Jim Arndt

They are not extinct but resting, pining for the Fjords.

M White

But still someone wants a grant
“Penguins Protected Against Climate Change”
“The unique wildlife of the Falkland Islands could be starting to feel the effects of climate change. Conservationists have launched a special scheme to monitor the impact on the region’s most famous residents – the penguins. Sky’s Emma Hurd reports.”


In my browser the maths came up as “a power law of the form S = C , where…”

David Carpenter

Another very interesting post Willis, how do you manage to do so much research? I am hard pressed to keep up!

Calvin Ball

Arrhenius in 1920, relates the number of species found to the area surveyed as a power law of the form S = C , where “S” is species count, “C” is a constant, “a” is habitat area, and “z” is the power variable (typically .15 to .3 for forests).

I think you have an exponent not showing up.

It appears the only species headed for extinction is the increasingly rare Alarmist Globulus Warmus.

Doug in Seattle

Since the 1970’s we have seen a fairly radical re-definition of the term species. Where we once considered all chinook salmon as a single species, we now see that every stream’s population of chinook salmon is regarded as a separate species.
This redefinition allows environmentalists to sue to have each individual stream listed as critical habitat for an endangered “species” when it is not possible to genetically differentiate that “species” from one in adjacent stream.
I suspect this is how Wilson gets his massively inflated numbers.

Henry chance

Who was taking records for us before America was discovered?
The KU Jayhawks rock. They are increasing as are poley bears.
The seirra Club is now reflecting on the issues around wind generators. Oh my. They are creating more danger for animals.

One error at least, in this paper, hit me almost immediately, though I had only read a few paragraphs. You need to correct this paragraph:
‘Wilson’s claim that 27,000 extinctions per year have been occurring since at least 1980 means that there should be 26 bird extinctions and 13 mammal extinctions per year, a total of 39 bird and mammal extinctions per year.’
You can’t have 27,000 per year and then state 26…. and 13…. per year since 1980. I suspect that there will be many such errors like this to catch and clean up. More careful editing is advised, and it would be easier in a much shortened paper.


Willis, I have to say that this lengthy piece of ill-informed nonsense seriously damages your credibility in my eyes. I’ll have to take another look at your previous piece on temperature records at Darwin, Australia, to see if it was as badly reasoned as this is.
1) it is simply not true that the last 500 years have seen “massive historical forest habitat reductions on all continents”. In fact, forest cover has fluctuated widely over the last 500 years.
2) you appear to think that we have a complete catalog of existing bird and mammal species. We don’t. We have no way of knowing how many species of birds or mammals may have gone extinct before they were ever discovered by science.
3) for birds, the idea that any significant population of probably-extinct birds such as Ivory-billed Woodpecker, Eskimo Curlew, or Bachman’s Warbler could escape the ever-growing legions of dedicated birders is prima facie absurd. If they were still out there, someone would have found them.
4) by focusing only on forest birds and mammals, you focus on a group of animals that are highly likely to be able to adjust to fluctuations in habitat. Forest communities are relatively uniform over tens of thousands of square miles. Populations of forest animals are similarly widespread, and difficult to completely eradicate.
I commend you for clearly stating what you were and were not attempting to prove … but I see no reason to accept your analysis as any more valid than Professor Wilson’s.


I saw a short TV snippet on the Falklands penguins on NZ news. The greenies all worried that climate change might affect them.
Sure it might, but I think the huge great fishing fleets catching all the fish and destroying the local ecosystem is rather a more important problem in all but the longest term. But not a single mention of commercial fishing was made. It was all about how changes to currents might drive fish away (of course there is a 50/50 chance any change will drive fish towards the Falklands, but we don’t go there).

Louis Hissink

Keep going – you are on a roll!
Species going extinct is one issue but the geological record shows that they are replaced by new ones, so the AGW believers, if they wish to be technically correct, should also explain how the new ones will come about.
Remember folks, the geological past is littered with mass-extinctions, followed by mass “creation” of new life forms, so to propose a new extinction but ignoring the necessary new species creation is, well, unscientific?

Jim Masterson

I think the power law should be something like: S = c*(A^z).

That’s OK – If 30,000 species are going to become extinct (due to global warming) in the next century – and these “highly educated college professors ‘studying’ ecology and biology say so – then we have 90 years to kill 29,998 more species.
Doable. Will take some concentrated expensive effort, but it’s achievable. But we must begin quickly. We must act now and not delay.
After, these biologists (who are widely peer-reviewed and published of course!) would NOT EVER be exaggerating or stretching the truth any, would they?

Ed Murphy

Florida Wildlife Commission Expects Record Number Of Manatee Popcycles In 2009
TALLAHASSEE, Florida — Biologists with the Florida Fish and Wildlife Conservation Commission’s (FWC) Fish and Wildlife Research Institute documented 419 manatee carcasses in state waters as of Dec. 11. This preliminary data indicates that the total number of manatee deaths for 2009 has surpassed the highest number on record for a calendar year.
Preliminary totals for 2009 will be available on Wednesday, Jan. 6, unless there is an unusually high number of manatee carcasses reported in the next two weeks. A statewide perspective on these numbers, including category breakdowns will be available at that time.

P Walker

There was a confirmed sighting of an Ivory Billed Woodpecker in Lousiana a few years ago .

Tremendous article, I printed it out and through it and will do so again. i’ve participated in the Audubon Christmas Bird Count for 15 yrs. I have also acted as a regional coordinator for my state bird count, overseeing 25 birders and thousands of breeding bird data records. I found that my own Audubon Society misused the data I and other birders collected, often during very cold weather that is typical of the Christmas bird counts. Here is my review of the Audubon Christmas Bird Count Report. As customary for the environmentalists, the Audubon report was a report of deception.
They scared the readers using January data, because it showed a big rise for the period, and scary-picked the temperature start and stop period, when in reality for the past 19 years the temperatures had decreased. Then they inaccurately portrayed many species as in trouble because of climate change, when in reality, the bird populations are increasing according to their own data.
After I wrote my blog report, I came upon Chris Knappengers report Audubon’s Bird-brained Conclusion: More Global Warming Misdirection and he studies the raw data in the Audubon report appendix, and came to the same conclusion, bird populations were generally increasing and healthy, yet the entire report was misleading! This is the state we now found ourselves in. And, it is accelerating at a rapid pace, where Nonsense and Scary conclusions from misrepresented data, or often total lies, are promulgated as FACTS. When they are in reality FARCE!


Habitat reduction due to global warming?
How many plant and animal species are there that don’t do just as well, if not better, in a warmer climate – just as long as it isn’t drier?

chris y

Willis- Fabulous post! In response to alarmist claims in blog comments, I have frequently requested listed names of even 1% of the predicted species extinctions over the past 30 years that were caused by climate change and/or habitat destruction. The people claiming 40K extinctions/year never respond.
Lomborg’s book has a chapter on species extinctions, and describes the origination of the 40K – 100K species/yr number as a complete WAG that morphed into consensus science. In other words, its absolutely specious drivel.
Recently Andy Revkin at Dot Earth commented that he would ask E.O. Wilson to provide a post on species extinctions. I have not seen any action on this yet. Your points raise serious challenges to Wilson’s central thesis.


Yangtze river dolphin?

John W.

Two points I’d appreciate your thought on:
1. As farmland was converted to residential housing developments, the land was essentially reforested as the homeowners planted trees. How might this have affected your findings?
2. At least in North Alabama, raptors became invasive and habituated to humans. (Sufficiently so that they posed a hazard to cats and yip dogs. Some might consider that beneficial. 8^) ) Does this play into your findings at all?

Another Brit

Cats. Forget global warming, cats have the upper hand My wife has 2 cats, natural born killers both of them. At least a bird and rodent a day each. The RSPB in this country refuses to acknowledge the impact cats have on the songbird population, as that would alienate a large part of their constituency. Personally I would sacrifice the cats, but I would suffer an extreme reaction from my spouse. Strange how people can reconcile hundreds of dead birds and small mammals on their doorsteps every year with the wellbeing of one cat.
Once global warming is canned, perhaps the next study should be on cats and the mortality rate of birds and mammals. Must be a way to tax cat owners surely?
Regarding penguins in the Falklands, another interesting study would be into the reduction of fish and krill stocks due to the explosion of commercial fishing since the Falklands War. At times there are hundreds of ships hoovering up everything with the “Conservation Zone.”

John W.

RACookPE1978 (14:43:41) :
Doable. Will take some concentrated expensive effort, but it’s achievable. But we must begin quickly. We must act now and not delay.

As an ordnance corps friend of mine says, there is no problem that can’t be solved by the suitable application of high explosives.
Where should we start? 8^)


I would say that at least the following continental birds have gone extinct because of habitat reduction:
Colombian Grebe Podiceps andinus
Bogotá Sunangel Heliangelus zusii
Turquoise-throated Puffleg Eriocnemis godini
Streseman’s Bristlethroat Merulaxis stresemanni
Slender-billed Grackle Quiscalus palustris
Bachman’s Warbler Vermivora bachmanni
There is also a number of species that are probably, but not quite certainly extinct for the same reason Ivory-billed Woodpecker and Imperial Woodpecker for example.


“wolfwalker (14:39:45) :
Willis, I have to say that this lengthy piece of ill-informed nonsense seriously damages your credibility in my eyes. I’ll have to take another look at your previous piece on temperature records at Darwin, Australia, to see if it was as badly reasoned as this is. ”
Smells like troll logic.


Splendid post. Not being educated on this matter, I just can’t figure out how the figures 26 and 13 were reached here:
“Wilson’s claim that 27,000 extinctions per year have been occurring since at least 1980 means that there should be 26 bird extinctions and 13 mammal extinctions per year, a total of 39 bird and mammal extinctions per year.”


“A recent study in Nature [Thomas 2004] stated that 37% of all species might soon go extinct because of habitat reduction due to global warming.”
The above statement is patently rubbish without any scientific investigation being necessary.
Mr Eschenbach treats the subject rightly with much more circumspection than it deserves.
Is Nature a scientific journal of record? If it was it isn’t any longer.


I lived on the Olympic Peninsula in Washington for a time, land of spotted owl fame. Some of this data would have been potentially helpful 20+ years ago. Doug in Seattle’s post is true, too, not just of Salmon but of spotted owls. There are at least 2 other ‘subspecies,’ and they are all over the west.
Interestingly, it turns out that deforestation isn’t the main problem with spotted owls anyway. It doesn’t help, but they are being out competed by Barred Owls moving in. So the argument morphs from, ‘we have to protect the entire ecosystem and there is such a delicate balance…,’ to, ‘sure nature is taking care of itself through natural selection, but we still need to protect this one little fastidious bird because we’d hate to see him go.’ Biodiversity is one thing, but the spotted owl is pretty much a religious icon at this point.
Now, I’m not in favor of deforestation, and I have nothing against spotted owls, but maybe we can see the first glimmer of light toward getting some necessary changes made to forestry regulations. Some day?


They say extinction is forever but….
I made a list of Australian mammal species that had been, at some time or other, declared extinct. I found 34 (a few of them of dubious species status). It was interesting that none of them had gone extinct in the last 50 years, the most recent being the Crescent Nailtail Wallaby, last seen in 1956.
Also interesting was the fact that in the last 50 years, at least 11 out of the 34 that were once thought extinct have been re-discovered, alive and well. In effect, the number of mammal extinctions in Australia in the last 50 years has been negative!
There may be more to re-discover. Most of the extinct species are small nocturnal animals, which were always rare and living in extremely remote and localised areas.


Any, and I mean ANY extinction of another species due to man’s greed, or ignorance is not acceptable. I hear what you are saying, but humans ARE the most destructive species.
Moving into land populated by say, tigers, then killing them if they kill your animals is insane… Hunting is NOT a SPORT, say any more than if I toss a grenade through your window while you are sleeping and claim we had a shootout.
Protect the species of this planet and the planet, execute the manipulators.

For the US, you’re missing the Ivory Billed Woodpecker, and that species almost certainly went extinct due to habitat destruction. The recent claims of its rediscovery are almost certainly specious.


The Passenger Pigeon was a forest dwelling bird driven to extinction in the US in the early 20th century.
The Ivory-billed Woodpecker. North American forest dweller. Probably extinct.


I had this discussion with the radical environmentalists at Realclimate asking that they name one species that went extinct as a result of Global Warming.
The only one they could come up with was the Central American Golden Toad.
(see link at: http://www.global-greenhouse-warming.com/extinct-golden-toad.html)
There is a study somewhere that draws the link to AGW but it’s tenuous to the extent it went extinct after a 1986 El Nino event. It probably died from loss of habitat or change in local climate as a result of human land use. The quote from the link above is as follows:
“The Monteverde cloud forest provided the only known habitat for the extinct golden toad which, along with the harlequin frog and 20 other amphibious species, became extinct around 1986-87. This coincided with a major El Niño event when climatic conditions in Costa Rica were particularly warm and dry.”

Willis Eschenbach

Calvin Ball (14:26:51) : edit

Arrhenius in 1920, relates the number of species found to the area surveyed as a power law of the form S = C , where “S” is species count, “C” is a constant, “a” is habitat area, and “z” is the power variable (typically .15 to .3 for forests).
I think you have an exponent not showing up.

Calvin (and Dearieme above), thanks, fixed.


Would be interesting to know how many new species have developed or reemerged in our industrialized age. Seems like I read, a few years ago, about a local species that was thought extinct but reemerged about 10 years later.

Willis Eschenbach

John K. Sutherland (14:37:53)
One error at least, in this paper, hit me almost immediately, though I had only read a few paragraphs. You need to correct this paragraph:

‘Wilson’s claim that 27,000 extinctions per year have been occurring since at least 1980 means that there should be 26 bird extinctions and 13 mammal extinctions per year, a total of 39 bird and mammal extinctions per year.’
You can’t have 27,000 per year and then state 26…. and 13…. per year since 1980. I suspect that there will be many such errors like this to catch and clean up. More careful editing is advised, and it would be easier in a much shortened paper.

See the numbers of bird species and mammal species as a percentage of total species …


Pretty much every species on Earth has lived through period both warmer and cooler than what we are experiencing now. They’ve lived through weather extremes, ice ages, ice clearing, and so on.
Also note that we have real data that shows the positive effects of CO2 and warming on the ecosphere.
Given this, the idea that the small amount of warming that we’re seeing will drive extinction events, now or in the forseeable future, is… amusing.


I think the numbers would change completely if you considered the nematodes. I have it on good authority that their used to be millions of species of spotted and striped nematodes, and now there are only hundreds of thousands.
My computer model told me so, so it must be true.


I would say that at least the following continental birds have gone extinct recently because of habitat destruction.
Podiceps andinus Colombian Grebe
Heliangelus zusii Bogotá Sunangel
Eriocnemis godini Turquois-throated puffleg
Merulaxis stresemanni Streseman’s Bristlethroat
Vermivora bachmanni Bachman’s Warbler
Quiscalus palustris Slender-billed Grackle
There are also several species that are probably, but not quite certainly extinct for the same reason, Imperial Woodpecker for example.
However it is easy to find examples of large-scale recent extinctions due to habitat destruction. The best (worst?) is probably the freshwater mussels of the eastern part of the USA. At least 26 species have gone extinct during the 20th century, exclusively because of habitat destruction, and another 30 are critically endangered. I can “list the corpses” if somebody is interested.

Layne Blanchard

I assume then, the majority of extinctions are of the family insecta? I’d like to nominate the fire ant for immediate extermination.

Rob R

In NZ, like Australia, many bird species have gone extinct and many are still threatened. Like you say predation is likely the main cause. e.g. by Humans (a number of species of Moa) and by destruction of food sources (the very large NZ native eagle which relied largely on Moa for food, but may also itself have been hunted by Maori). The Huia (bird) was driven to extinction by collection for museums etc and for adornment (attractive feathers). Predation has also occured by introduced dogs, cats, rats, bushtail possums, stoats and ferrets.
But in the modern day a number of species and sub-species have been maintained by active human intervention (e.g. the Takahe, the Kakapo, and the Chatham Island Black Robin). Perhaps you need to discuss active intervention (conservation) and belated habitat protection and add these to your list. This activity must also be happening to some extent in a continental setting, just as it has been becoming more common during recent decades in the Islands of New Zealand.
Rob R


@Josualdo: I’m assuming that the conversion from “27,000 extinctions per year” to “26 bird extinctions and 13 mammal extinctions per year” was done by multiplying the ratio of birds species/all species and mammal species/all species. (There is a statement about half way through “Bird species make up about .1% of all species, and mammal species are about .05% of all species (IUCN 2000)”
The actual values I calculated that Eschenbach used are reasonably close to the quoted values: birds =0.0963% of all species, and that mammals =0.0481% of all species.
Readability of this paper would certainly be improved if the explanation and IUCN reference wer provided back where the 27000 to 26/13 conversions were actually performed.

Steven Kopits

A very interesting piece of research embodying both good research technique and logical process. Nicely written and genuinely educational.
It states what one might have suspected: predation, not habitat reduction, is the key source of extinction. Of course, loss of habitat almost certainly means fewer numbers of a given species that depend on the habitat. That is itself a loss, although not of extinction per se.
The record also shows remarkable resiliance in the face of temperature change. Take, for example, Wisconsin. Average temperatures there have varied by 7 deg F over on an annual basis over a very short period of time, as they did from 1996 to 1998. Thus, temperatures in Wisconsin, on average, every day, were seven degrees hotter in 1998 than in 1996–and yet no local extinctions were reported to the best of my knowledge.
This suggests that emphasis on climate change, for those interested in extinctions, is largely misplaced. Invasive species, like the pythons in the Everglades or the lionfish off the tropical east coast, are the critical issues. If we wish to defend our native biodiversity, we must take on the invaders directly. An obsession with climate change at the expense of more down-to-earth environmental issues will paradoxically produce precisely the harm that global warming advocates seek to avoid.

David Alan

I would like to see articles like this posted by Willis Eschenbach find more attention in main stream media.
Instead, articles like the one below here ran by the Telegraph seems to get more attention, solely for its alarming, nonsensical, highly predictive and unsubstantiated claims.
[ Animals ‘on the run’ from climate change.
Plants and animals will need to move at an average rate of a quarter of a mile a year to escape climate change over the course of this century, according to scientists.
For species in flatter, low-lying regions such as deserts, grasslands, and coastal areas, the pace of the retreat could exceed more than half a mile a year, it is claimed.
Creatures and plants only able to tolerate a narrow range of temperatures will be most vulnerable, said the researchers.
Those unable to match the migration speeds needed to escape the effects of global warming could vanish into extinction.
Plants in almost a third of the habitats studied were thought to fall into this category, the scientists reported in the journal Nature.
Fragmentation by human development made the situation more perilous in some areas as it left many species with “nowhere to go”.
The researchers combined data on climate and temperature variation worldwide with projections to calculate the “temperature velocity” for different habitats. This is a measure of how fast temperature zones are moving across the landscape as the planet warms – and how quickly plants and animals will need to migrate to keep up.
The expected temperature velocity for the whole of the 21st century was 0.26 miles per year.
Author Dr Chris Field, director of the Carnegie Institution’s Department of Global Ecology in Stanford, California, said animals will be forced to migrate while many plants will die out.
“Expressed as velocities, climate-change projections connect directly to survival prospects for plants and animals. These are the conditions that will set the stage, whether species move or cope in place,” he said.]
What a bunch of trash.
Its articles like this from the Telegraph that supports my call for a complete and total boycott main stream media.
Thank you Willis for your factual presentation of the facts.


The claim that there has not been enough recent extinctions (say since 1980) is specious, simply because it is rarely known exactly when a species goes extinct. Near the end they are normally extremely rare, and hence difficult to find, and usually it takes a long time after the last record, often a couple a decades, before one can be completely sure that a species is extinct. As it is at least about 30 mammals and about 60 birds went extinct during the twentieth century.


I would say that at least the following continental birds have gone extinct recently because of habitat destruction.
Podiceps andinus Colombian Grebe
Heliangelus zusii Bogotá Sunangel
Eriocnemis godini Turquois-throated puffleg
Merulaxis stresemanni Streseman’s Bristlethroat
Vermivora bachmanni Bachman’s Warbler
Quiscalus palustris Slender-billed Grackle
At least four of these were forest dwellers.
There are also several species that are probably, but not quite certainly extinct for the same reason, Imperial Woodpecker for example.
However it is easy to find examples of large-scale recent extinctions due to habitat destruction. The best (worst?) is probably the freshwater mussels of the eastern part of the USA. At least 26 species have gone extinct during the 20th century, exclusively because of habitat destruction, and another 30 are critically endangered. I can “list the corpses” if somebody is interested.


I would tend to think that if you destroy habitat, the animals will rapidly move in the opposite direction. Doing so will increase the density of such species and thus increase their respective reproduction rates. This will give the species much more time to find/adapt to their new environment.
When you think that natural extremely rapid forest fires that happened often in the past did not even drive extinctions, how can a very slow profit driven deforestation drive extinction?
I do agree that the most damage to species happened when we started exploring the earth. Eventually this will result in a sort of equilibrium. Some species can simply not live under different climates and all species need a male and female to reproduce (at least mammals and birds). Maybe we should keep an eye on those exotic pet breeder’s and exporters.

Jeff B.

This is one of those Global Warming hysteria points because the average Joe has no way of ever verifying a global event such as extinction of some specific species, especially if that species is not local. So, fantastic quotes of mass extinction sound sufficiently scary to dupe the willing.
Climategate is helping to wake up average Joe to challenge the veracity of any and all AGW claims, particularly the sensational. Indeed, where are the corpses?