Recently, I was astonished when I came across an article titled, Are We in a ‘Sixth Great Extinction’? Maybe Not, by Ross Pomeroy, an editor of RealClearScience and a zoologist and conservation biologist by training. The author’s candor and intellectual honesty are refreshing:
The notion that humans are erasing species off the face of the Earth at near unprecedented levels is a perennial story that has been blared in the media for more than two decades. In the year 2000, the United Nations’ Millennium Ecosystem Assessment estimated that species are going extinct 1,000 times faster than they naturally do, and that this rate could increase to 10,000 times. These rates translate to between 17,000 and 140,000 species going extinct each year by some estimates…
…[M]y acceptance of those estimates was recently shaken when I came across a simple fact. Over the last five hundred years, there have been just 875 confirmed extinctions. Why so few, when some scientists have insisted there should have been millions?
There’s no doubt that humans have caused and are causing animals to go extinct, but to compare the current situation to previous mass extinctions is misleading. As Sarah Kaplan reported in the Washington Post last year:
The losses of the past century account for only about 1 percent of the roughly 40,000 known vertebrate species — a statistic that pales in comparison to the level of destruction seen during previous mass extinction events. Even in the least of them, between 60 and 70 percent of species were killed off. During the end-Permian event about 250 million years ago, known as “the Great Dying,” that number was more than 90 percent.
In her recent book Resurrection Science, journalist M.R. O’Connor offered a reason why the hyped notion of a sixth mass extinction persists.
“The field of conservation biology is a crisis discipline,” she wrote, suggesting that the field is inclined to forecast doom and gloom in order to promote needed environmental protections.
“Conservationists themselves have said that the field breeds a culture of despair,” she continued. “And at times, their pessimism threatens to undermine the cause. ‘A society that is habituated to the urgency of environmental destruction by a constant stream of dire messages from scientists and the media will require bigger and bigger hits of catastrophe to be spurred into action,’ wrote biologists Ronald Swaisgood and James Sheppard in 2010.”
Ross Pomeroy’s honesty is commendable. It is rare to find a science writer who is willing to admit that he/she may have been wrong on an issue relating to public policy.
Pomeroy’s article confirms suspicions which I voiced last year, in a post on Uncommon Descent:
Studies propagating the myth of the Sixth Great Extinction continues to be breathlessly repeated in the media. Just last week, a Live Science report by Laura Geggel, titled, Here’s More Proof Earth Is in Its 6th Mass Extinction [June 19, 2015], was posted on Yahoo. The report trumpeted the findings of a new study purporting to clinch the case and silence the doubters once and for all…
Curious about the study, I dug up … the abstract of the study, which is titled, Accelerated modern human-induced species losses: Entering the sixth mass extinction (Science Advances 19 Jun 2015: Vol. 1, no. 5, e1400253) and is co-authored by Gerardo Ceballos, Paul R. Ehrlich, Anthony D. Barnosky, Andrés García, Robert M. Pringle and Todd M. Palmer…
The full text of the study is available here. However, as soon as I read the abstract, I could see immediately that there were some major flaws in the study’s reasoning.
Flaws in the 2015 study by Ceballos et al.
FLAW #1: The study fails to mention that scientific estimates of the current rate of species extinctions are wildly divergent, varying by a factor of 100
The first point I’d like to make is that scientists have a very poor idea how rapidly species are actually dying out as a result of human activity. Ronald Bailey, a science correspondent for Reason magazine, has pointed out that many estimates of the rate at which species are becoming extinct are highly inflated, in a carefully documented article titled, Predictions of a Man-Made Sixth Mass Extinction May Be Exaggerated (Reason, August 1, 2014). For instance, a recent study by Rodolfo Dirzo et al. (Science 345, pp. 401-406, 2014) claimed that the world is “likely losing 11,000 to 58,000 species annually.” At the higher rate, something like 40 percent of all animal species will be gone by 2050. However, according to the most recent and authoritative estimate by Stuart Pimm et al. (Science 30 May 2014: Vol. 344 no. 6187), the current extinction rate of species is actually 100 out of every million species, per year – which means that if there are five to ten million species on Earth, about 500 to 1,000 species are going extinct every year. That’s about 20 to 100 times lower than Dirzo’s extravagant estimate. What’s more, very few (if any) of these extinctions can be linked to global warming.
Note the high level of variation here: Pimm estimates that the number of species going extinct each year may be as low as 500, while Dirzo claims it may be as high as 58,000. That’s a ridiculous level of scientific uncertainty…
FLAW #2: If we exclude one-off extinctions occurring on islands between 1500 and 1980, the rate of extinctions caused by human activities drops to only about 5 times higher than the background rate, not 114 times as claimed by Ceballos et al.
In their study, Ceballos et al. chose to focus on vertebrates, the best-studied group of animals, and they deliberately counted only those species of animals that were officially listed as being extinct, or that were likely to have become extinct, but not yet officially verified. Methodologically, their procedure was commendably cautious. What they overlooked, however, was that nearly all of the officially recorded extinctions during the last 500 years took place on islands (including the geographically isolated “island continent” of Australia), as a result of the introduction of alien predators and uncontrolled hunting. … If we leave out island extinctions, then the rate of man-made extinctions in the past 500 years drops dramatically to less than ten times the background rate.
FLAW #3: Even if the figures cited by Ceballos et al. were correct, it would be absurd to infer that a sixth great extinction was underway
But let’s suppose that Ceballos et al. are right after all in their estimate of the rate of man-made extinctions. They claim that it is about 100 times the natural background rate of two out of every 10,000 species per century. That would mean that 200 out of every 10,000 species, or 2% of all species on Earth, are becoming extinct every century. But at that rate, it would take more than two millennia for half of the Earth’s species to die off, in a sixth great extinction. That’s over 2,000 years.
Now, any scientist will tell you that 2,000 years is a mere eye-blink in geological terms, and that many of the previous five great extinctions took place over a considerably longer period. That may be so, but in human technological terms, 2,000 years is an eternity. (Think of how we lived 2,000 years ago: paper had only just been invented, the average lifespan was about 35 years, and our scientific knowledge was virtually nil.) My point is that even if we are killing off 2% of the Earth’s species every century, it’s highly likely that we’ll have figured out how to halt this ecological destruction by the year 2100 or 2200. After all, think of how far we’ve come in the last century: radio (1900), the airplane (1903), television (1925), the computer (1936), satellites (1957), the Internet (1969), the personal computer (1982) and the World Wide Web (1989), to name just a few inventions that have shaped our lives. What the proponents of a sixth great extinction are really saying is that 2,000 years from now, we still won’t have figured out a way to halt the environmental destruction that we are causing now. That’s absurdly pessimistic.
In other news, the global warming Website Watts Up With That? (WUWT) has recently exposed three more eco-myths that continue to be widely circulated on the Internet.
Myth #1: Polar bear numbers are declining dangerously
The first myth relates to polar bears, whose populations (it turns out) are not crashing after all. Here’s a brief excerpt from a WUWT post titled, Ten dire polar bear predictions that have failed as global population hits 20-31k (February 25, 2016) by Dr. Susan Crockford:
While polar bears may be negatively affected by declines in sea ice sometime in the future, so far there is no convincing evidence that any unnatural harm has come to them. Indeed, global population size (described by officials as a “tentative guess“) appears to have grown slightly over this time, as the maximum estimated number was 28,370 in 1993 (Wiig and colleagues 1995; range 21,470-28,370) but rose to 31,000 in 2015 (Wiig and colleagues 2015, [pdf here] aka 2015 IUCN Red List assessment; range 20,000-31,000)…
Polar bears are not fragile canaries in an Arctic climate-change coal mine but resilient and adaptable predators remarkably suited to their highly variable habitat.
Myth #2: The destruction of Easter Island was caused by the islanders chopping down all the trees
The second myth is the eco-fable that deforestation by the local inhabitants of Easter Island caused habitat destruction and led to the depopulation of the island. This eco-myth was popularized in Easter Island, Earth Island by Paul Bahn and John Flenley (1992), and in Jared Diamond’s Collapse: How Societies Choose to Fail or Succeed (2005). Here’s an excerpt from a WUWT post titled, Science debunks the fable of Easter Island, which quotes from an article by Larry Kummer, from the Fabius Maximus website:
Summary: The fast Polynesian expansion across the Pacific from Samoa to South America is one history’s greatest achievements of exploration. Conducted with primitive technology, they colonized almost every suitable island in the Pacific. Equally remarkable in a different way is how the sad story of the last and least-suitable of their settlements has been twisted into an eco-fable. Here is that story and the long effort of a few scientists to bring the truth to light…
One of the more complete tellings of the full story is The Statues that Walked: Unraveling the Mystery of Easter Island by Terry Hunt and Carl Lipo (2011). From the publisher’s summary:
“… Far from irresponsible environmental destroyers, they show, the Easter Islanders were remarkably inventive environmental stewards, devising ingenious methods to enhance the island’s agricultural capacity. They did not devastate the palm forest, and the culture did not descend into brutal violence.“Perhaps most surprising of all, the making and moving of their enormous statutes did not require a bloated population or tax their precious resources; their statue building was actually integral to their ability to achieve a delicate balance of sustainability. The Easter Islanders, it turns out, offer us an impressive record of masterful environmental management rich with lessons for confronting the daunting environmental challenges of our own time.”
The people of Easter Island, like so many others, were wrecked by the West: we gave them pandemic diseases, then depopulating slave raids and ecological devastation (conversion of the island to a sheep range, for which it was poorly suited). This eco-fable is an outrageous example of blaming the victim.
Myth #3: Ocean acidification is endangering the planet
Finally, a new post on WUWT exposes the myth that ocean acidification poses a danger to the planet:
A new paper published in the ICES Journal of Marine Science puts the issue of “ocean acidification” to the test, and finds that there has been significant exaggeration in the issue…
From an article in The Times:
An “inherent bias” in scientific journals in favour of more calamitous predictions has excluded research showing that marine creatures are not damaged by ocean acidification, which is caused by the sea absorbing carbon dioxide from the atmosphere.It has been dubbed the “evil twin of climate change” and hundreds of studies have claimed to show that it destroys coral reefs and other marine life by making it harder for them to develop shells or skeletons.
The review found that many studies had used flawed methods, subjecting marine creatures to sudden increases in carbon dioxide that would never be experienced in real life.
“In some cases it was levels far beyond what would ever be reached even if we burnt every molecule of carbon on the planet,” Howard Browman, the editor of ICES Journal of Marine Science, who oversaw the review, said. He added that this had distracted attention from more urgent threats to reefs such as agricultural pollution, overfishing and tourism…
Dr Browman invited scientists around the world to contribute studies on ocean acidification for a special edition of his journal. More than half of the 44 studies selected for publication found that raised levels of CO2 had little or no impact on marine life, including crabs, limpets, sea urchins and sponges…
In the article from the Times, the lead author [Howard Browman] also has this to say:
…He said that a handful of influential scientific journals and lobbying by international organisations had turned ocean acidification into a major issue. The bias in favour of doom-laden articles was partly the result of pressure on scientists to produce eye-catching work, he added.
Doom-and-gloom bias in the publicity-hungry science media? Who would have thought it?
Comments are welcome.