How Often Do Species Go Extinct?

Agresti, J. D. (2011, November 28). How Often Do Species Go Extinct? Retrieved from
Agresti, James D. “How Often Do Species Go Extinct?” Just Facts. 28 November 2011. Web. 30 October 2020.<>.
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James D. Agresti, “How Often Do Species Go Extinct?” Just Facts. November 28, 2011.
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Agresti, James D. “How Often Do Species Go Extinct?” Just Facts. November 28, 2011.

By James D. Agresti
November 28, 2011

“Overall, species loss is now occurring at a rate 1,000 times greater than the natural background rate,” warns Al Gore in the Academy Award-winning documentary, An Inconvenient Truth (see clip below). Similarly, Michael J. Novacek of the American Museum of Natural History wrote in a 2007 book (page 46) that “species are going extinct at thousands of times the background extinction rate,” and we are “thus likely to lose 30 to 50 percent of all living species within this century.”

Such dire portrayals are incompatible with concrete data on species extinctions. In a recently published paper in the journal Diversity and Distributions, the authors analyzed the “actual historical record of extinctions” and found that a total of 190 birds and land-dwelling mammals have gone extinct since the year 1500. The data also showed that only three of these mammals and six of these birds lived on continents. The rest lived on islands, where populations are small and geographically restricted. As the authors explain:

The three extinct mammals represent approximately 0.08% of the continental species pool. Even if we assume that all three went extinct in the past 100 years (vs. 500 year), it would take, at this rate, 1235 years for 1% of continental mammals to go extinct. Similarly for birds, the six species represent 0.062% of the 9672 species pool and it would take 1613 years to lose 1% of extant species at current rates even if the recorded extinctions all took place over the last 100 years.

This is a far cry from Novacek’s claim that we are “likely to lose 30 to 50 percent of all living species within this century.” Gore, Novacek, and many other environmentalists either don’t understand or neglect to mention that this “natural background rate” they speak of is a fossil-based estimate burdened with so many assumptions that a 2005 Cambridge University Press book on biodiversity (page 139) states that no “serious” attempt has been made to “judge the reliability” of this figure because the “uncertainties at each stage of the calculation” would make the effort worthless. The book goes on to explain, “Probably no one will be surprised if this estimate is off by a factor of 10 or even 100.”

Based upon the data above, it may be off by even more than this. For more details, see my commentary on this subject in American Thinker.

  • December 1, 2011 at 5:13 PM

    A species is not fixed, it depends upon who’s classifying it and when. Sixty years ago when the splitters were ascendent, there were 23 species of bear. Now with the lumpers ascendent there are only 3 species: white, brown, and black. Have 87% of the species of bear become extinct? No, the classification had been changed.

  • August 8, 2012 at 6:30 PM

    That is a foolish way of analyzing the data. Isn’t it possible that ALL species are simultaneously decreasing until the point that all of them start to become extinct within a short time period?

    • August 9, 2012 at 12:44 PM

      On the contrary, we’re talking about a sample period of 500 years. It would be foolish to assume that such a lengthy period with so few extinctions is only an anomaly while claiming without evidence that mass extinctions are just around the corner and are going to occur “within a short time period.”

  • January 4, 2016 at 3:16 AM

    First of all, anyone who believes a word Al Gore says with anything regarding science or Earths environment are fools. He orchestrated the biggest lie known to date in regards to human impact climate change and got caught. Nobel Prize winning scientists and some of best environmental scientist in the world have said anything coming from Gore or The Intergovernmental Panel on Climate Change (IPCC) should never be considered anything more political talk or lies. I didn’t read or watch what he said in the article listed, so what he said could be true or it might not. By simply listing Al Gore (or IPCC for any title) though, the content lost all credibility. If you don’t believe me….well here are some of best scientist in the world and coming straight from their mouth…

    “Please remain calm: The Earth will heal itself — Climate is beyond our power to control…Earth doesn’t care about governments or their legislation. You can’t find much actual global warming in present-day weather observations. Climate change is a matter of geologic time, something that the earth routinely does on its own without asking anyone’s permission or explaining itself.” — Nobel Prize-Winning Stanford University Physicist Dr. Robert B. Laughlin, who won the Nobel Prize for physics in 1998, and was formerly a research scientist at Lawrence Livermore National Laboratory.

    “I view Climategate as science fraud, pure and simple,” said noted Princeton Physicist Dr. Robert Austin

    “We maintain there is no reason whatsoever to worry about man-made climate change, because there is no evidence whatsoever that such a thing is happening.” — Greek Earth scientists Antonis Christofides and Nikos Mamassis of the National Technical University of Athens’ Department of Water Resources and Environmental Engineering.

    Geologist Dr. Don Easterbrook, a professor of geology at Western Washington University, summed up the scandal on December 3, 2010: “The corruption within the IPCC revealed by the Climategate scandal, the doctoring of data and the refusal to admit mistakes have so severely tainted the IPCC that it is no longer a credible agency.”


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