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Reality Check: Mass extinction fears ‘have little support from science’ – Claimed losses ‘are absurdly large’

About the mass extinctions supposedly occurring now

By Larry Kummer

Summary: More fears fed by activists. (See: ‘Terror being waged on wildlife’, leaders warn) As the papers cited below show, they have little support from science – but are seldom rebuked by scientists. Each round of such exaggerated claims erodes away the public’s trust. The leaders of science institutions show little interest in fixing this problem. We cannot afford to have science’s credibility squandered for short-term political gains.

The Sixth Extinction

“Biodiversity is decreasing at an alarming rate with more than 10,000 species disappearing each year.”
— Opening speech at the opening session of the 48th Plenary of the IPCC by Jian Liu (UN Environment’s Chief Scientist), 1 October 2018.

This is a bad beginning for the rollout of the IPCC’s SR15, the special report “Global Warming of 1.5 ºC.” It is a claim from leftist advocates based on zombie science (much like Zombie Economics on the Right): with mysterious origins and impossible to kill. Since the numbers are made-up, they vary widely.

“Every hour, three species disappear. Every day, up to 150 species are lost. Every year, between 18,000 and 55,000 species become extinct.  The cause: human activities. …Climate change is one of the major driving forces behind the unprecedented loss of biodiversity.“
— Speech on 21 May 2007 by Ahmed Djoghlaf, then Executive Secretary of the Convention on Biological Diversity under the United Nations Environment Programme (UNEP).

“If there are 100,000,000 different species on Earth, and the Extinction rate just is 0.01% per year, then 10,000 species go extinct every year.
— Website of the World Wildlife Federation. The WWF’s claims are uncritically repeated (a lot) by journalists (e.g., in USA Today).

Those numbers are absurdly large. Also, there are many causes of species extinction. Climate change is today a far smaller factor than habitat loss and pollution (to name just two). Three decades of exaggerations like this have eroded away much of scientists’ credibility. No matter if these are noble lies or just excess enthusiasm, they decrease our ability to prepare for the severe environmental damage almost certain as the world’s population grows to 10 billion (or more).

Here is a look at the state of the science at present. As usual, it is a debate about models — with the key facts uncertain and the key factors poorly understood.

The science

There is little support in the peer-reviewed literature for those wild numbers about current extinction rates. Let’s start with the hard facts as described by Endangered Species International — “More than 16,000 species are threatened to become extinct in the near future.” “Of the 44,838 species assessed worldwide using the IUCN Red List criteria, 905 are extinct {was 784 in 2006} and 16,928 are listed as threatened to be extinct.”

Modeling can produce far larger estimates, albeit they vary by an order of magnitude. But they have only weak empirical foundations, as they rest on poorly understood dynamics with weak estimates of key factors. Worse, they are impossible to prove or disprove today. Here are a few of the papers saying that extinction rates are high and warning about future rates of extinction. Note they discuss extinction rates in terms of multiple of the “natural” or “background” rate,  E/MSY (extinctions per million species-years), or per cent extinct at some future point. They do not give sensational numbers of “species going extinct every day.”

“Using projections of species’ distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth’s terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a power-law relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15–37% of species in our sample of regions and taxa will be ‘committed to extinction’.”
— “Extinction risk from climate change” by Chris D. Thomas et al. in Nature, 8 January 2004. Gated; open copy here. Fourteen years later, 30% of the time until their 2050 target, we see little evidence of the predicted mass extinctions.

“The consensus of scientists is that the current global rate of species extinctions is on average somewhere between 100 and 1,000 times greater than pre-human levels (the natural background extinction rate) …”
— Sustaining Life: How Human Health Depends on Biodiversity, edited by Eric Chivian and Aaron Bernstein (2008). This estimate remains the consensus ten years later.

“In sum, present extinction rates of ~100 E/MSY and the strong suspicion that these rates miss extinctions even for well-known taxa, and certainly for poorer known ones, means present extinction rates are likely a thousand times higher than the background rate of 0.1 E/MSY.
— “The biodiversity of species and their rates of extinction, distribution, and protection” by S. L. Pimm et alScience, 30 May 2014. Ungated copy.

“If we follow our current, business-as-usual trajectory [representative concentration pathway (RCP) 8.5; 4.3°C rise], climate change threatens one in six species (16%).”
— “Accelerating extinction risk from climate change” by Mark C. Urban in Science, 1 May 2015. Gated. Open copy here. That’s the high-end estimate since RCP8.5 is the worst case scenario in the IPCC’s AR5. So it is unlikely (details here).

“Even under our assumptions, which would tend to minimize evidence of an incipient mass extinction, the average rate of vertebrate species loss over the last century is up to 100 times higher than the background rate.”
— “Accelerated modern human–induced species losses: Entering the sixth mass extinction” by Gerardo Ceballos and Paul R. Ehrlich et al, Science Advances, 19 June 2015. They note that only 477 vertebrates have gone extinct since 1900.

Papers giving a more optimistic perspective

There are quite a few of these. Here are two.

Re-assessing current extinction rates” by Neil Stork in Biodiversity and Conservation, February 2010. Gated. Open copy. He cites the overwhelming peer-reviewed research evidence that claims of mass extinctions occurring today are exaggerated or false, and explains the reasons for these errors. Conclusions …

“So what can we conclude about extinction rates? First, less than 1% of all organisms are recorded to have become extinct in the last few centuries and there are almost no empirical data to support estimates of current extinctions of 100 or even one species a day.

“Second, the most frequently used predictions for global extinction rates are still largely based on the species–area relationship and the fact that large areas of forests (in particular) are being converted. As Lewis (2006) suggested these and the first models of the impacts of climate change on biodiversity, are first passes with subsequent more sophisticated analyses frequently reducing first estimates of extinction rates (see Table 1). With the increasing evidence that some species appear to survive in regrowth forests (Chazdon et al. 2009) the key question is how long are the time lags to extinction for those remaining species which are unable to survive in regrowth or fragmented forests?

“Third, the evidence is so overwhelming that extinction threats vary for different groups of organisms and different faunas and floras that it is surprising that there are still some who seek to draw conclusions on global extinction rates for all organisms based on the knowledge of just a few very highly threatened groups. …

“In contrast to the lack of evidence for mass global extinctions, there is considerable evidence for widespread loss of species at the local and regional level and I suggest that and the consequences of such losses on ecosystem function should be key foci for future research.”

Species–area relationships always overestimate extinction rates from habitat loss” by Fangliang He and Stephen P. Hubbell in Nature, 19 May 2011. Gated.

“Extinction from habitat loss is the signature conservation problem of the twenty-first century. Despite its importance, estimating extinction rates is still highly uncertain because no proven direct methods or reliable data exist for verifying extinctions.

“The most widely used indirect method is to estimate extinction rates by reversing the species–area accumulation curve, extrapolating backwards to smaller areas to calculate expected species loss. Estimates of extinction rates based on this method are almost always much higher than those actually observed. This discrepancy gave rise to the concept of an ‘extinction debt’, referring to species ‘committed to extinction’ owing to habitat loss and reduced population size but not yet extinct during a non-equilibrium period.

“Here we show that the extinction debt as currently defined is largely a sampling artefact due to an unrecognized difference between the underlying sampling problems when constructing a species–area relationship (SAR) and when extrapolating species extinction from habitat loss. The key mathematical result is that the area required to remove the last individual of a species (extinction) is larger, almost always much larger, than the sample area needed to encounter the first individual of a species, irrespective of species distribution and spatial scale. We illustrate these results with data from a global network of large, mapped forest plots and ranges of passerine bird species in the continental USA; and we show that overestimation can be greater than 160%.

“Although we conclude that extinctions caused by habitat loss require greater loss of habitat than previously thought, our results must not lead to complacency about extinction due to habitat loss, which is a real and growing threat.”

An important reminded by John C. Briggs (Prof Marine Science, U South FL) in Science, 14 November 2014.

“Most extinctions have occurred on oceanic islands or in restricted freshwater locations, with very few occurring on Earth’s continents or in the oceans.”

Dodo by Frederick William Frohawk from Waler Rothschild’s Extinct Birds.

Non-technical articles about these questions

Even the leftists at the BBC ask if “Biodiversity loss: How accurate are the numbers?” (2012).

“Current estimates of the number of species can vary from, let’s say, two million species to over 30 or even 100 million species,” says Dr Braulio Dias, executive secretary of the Convention on Biological Diversity. “So we don’t have a good estimate to an order of magnitude of precision,” he says. But if it’s really true that up to 150 species are being lost every day, shouldn’t we expect to be able to name more than 801 extinct species in 512 years?”

For a good summary of the science, see “Global Extinction Rates: Why Do Estimates Vary So Wildly?” by Fred Pearce at YaleEnvironment360, August 2015 — “Is it 150 species a day or 24 a day or far less than that? Prominent scientists cite dramatically different numbers when estimating the rate at which species are going extinct. Why is that?”

For a non-technical summary of these and actual good news about extinction rates (i.e. that the news is bad but not catastrophic) see “Rethinking Extinction” by Stewart Brand at Aeon, April 2015 – “The idea that we are edging up to a mass extinction is not just wrong – it’s a recipe for panic and paralysis.” Brand edited the Whole Earth Catalog (1968-74). Now he is president of the Long Now Foundation and co-founder of the Revive and Restore project in San Francisco. Also see his articles about de-extinction.

In their 2015 Report to the Club of Rome, On the Edge: The State and Fate of the World’s Tropical Rainforests, Claude Martin and Thomas E. Lovejoy walked back on some of the WWF’s claims. Martin is a former director of WWF International. Lovejoy is “the Godfather of Biodiversity” and a professor of environmental science at George Mason U.

“Ariel Lugo found that the massive deforestation in Puerto Rico, which lost up to 99% of the primary forest area, did not lead to the massive extinction expected by Myers et al. After 500 years of human pressure, only seven bird species became extinct, which corresponded to 11.6% of the indigenous bird fauna. Introduced species had even increased the number of species on the island.

“Similar observations were been made in El Salvador, which had lost more than 90% of its natural forest even before the war of the 1980s and since then experienced some forest resurgence. Despite massive forest cover loss, El Salvador seems to have preserved impressive levels of biodiversity …Of the 508 bird species …at the end of the 1990s those in danger of extinction numbered 117, but only 3 were then believe to be extinct.”

Who are those extinct animals? Mostly bugs.

For the most accurate list of extinct and endangered species, see the IUCN Red List of extinctions. Wikipedia posts this in a more easily viewed form.

Seldom mentioned in the alarmist articles is the big fact: most Animalia are bugs.

“There is a story, possibly apocryphal, of the distinguished British biologist, J.B.S. Haldane, who found himself in the company of a group of theologians. On being asked what one could conclude as to the nature of the Creator from a study of his creation, Haldane is said to have answered, ‘An inordinate fondness for beetles.’”
— “Homage to Santa Rosalia or Why Are There So Many Kinds of Animals?” by G. E. Hutchinson in The American Naturalist, May-June 1959. Hat tip to the Quote Investigator.

“It has been suggested that we do not know within an order of magnitude the number of all species on Earth. Roughly 1.5 million valid species of all organisms have been named and described. Given Kingdom Animalia numerically dominates this list and virtually all terrestrial vertebrates have been described, the question of how many terrestrial species exist is all but reduced to one of how many arthropod species there are. With beetles alone accounting for about 40% of all described arthropod species, the truly pertinent question is how many beetle species exist.
— “New approaches narrow global species estimates for beetles, insects, and terrestrial arthropods” by Nigel E. Stork et al. in PNAS, 16 June 2015.

Can we even count the number of animals?

Calculations of extinction rates require knowing the number of species. Estimates vary widely. But scientists are making progress. Slow progress. None of the estimates are remotely close to the WWF claim (above) that there are 100 million species.

8.7 Million: A New Estimate for All the Complex Species on Earth” by Daniel Strain, Science, 26 August 2011. Ungated copy here.

Can We Name Earth’s Species Before They Go Extinct?” by Mark J. Costello, Robert M. May, and Nigel E. Stork in Science, 25 Jan 2013. Gated. Open copy here.

“Some people despair that most species will go extinct before they are discovered. However, such worries result from overestimates of how many species may exist, beliefs that the expertise to describe species is decreasing, and alarmist estimates of extinction rates. We argue that the number of species on Earth today is 5 ± 3 million, of which 1.5 million are named. New databases show that there are more taxonomists describing species than ever before, and their number is increasing faster than the rate of species description. …Extinction rates are, however, poorly quantified, ranging from 0.01 to 1% (at most 5%) per decade.”

Despite the rebuttals, fears that “most species will go extinct before they are discovered” are still repeated, and the rebuttals ignored. As in “Species, extinct before we know them?” by Alexander C.Lees and Stuart L. Pimm in Current Biology.

Also, some scientists are skeptical about the progress: “Global species richness estimates have not converged” by M. Julian Caley et al. in Trends in Ecology and Evolution, April 2014. Gated. Open copy here. Opening …

“Our ability to estimate the total number of species that live on our planet, or in any of its major habitats, realms, or ecosystems, has immense practical and symbolic importance. Global species richness, whether estimated by taxon, habitat, ecosystem, or the entire planet, is a key metric of biodiversity. In the absence of agreed, and relatively certain, estimates of global species richness, we are unable to adequately understand the magnitude of what is at risk from global change during the Anthropocene, or our successes and failures in mitigating those risks and remediating impacts.

“{I}f our ability to estimate species richness has been improving, our estimates should be converging, and the uncertainty around them progressively decreasing. Indeed, such convergence in global species richness estimates has recently been claimed. Here we review published estimates of global species richness, but argue instead that these estimates have failed to converge over more than six decades of research.”

But there is progress on the bug front: “New approaches narrow global species estimates for beetles, insects, and terrestrial arthropods” by Nigel E. Stork et al. in PNAS, 16 June 2015.

“It has been suggested that we do not know within an order of magnitude the number of all species on Earth. Roughly 1.5 million valid species of all organisms have been named and described. Given Kingdom Animalia numerically dominates this list and virtually all terrestrial vertebrates have been described, the question of how many terrestrial species exist is all but reduced to one of how many arthropod species there are. With beetles alone accounting for about 40% of all described arthropod species, the truly pertinent question is how many beetle species exist.

“Here we present four new and independent estimates of beetle species richness, which produce a mean estimate of 1.5 million beetle species. We argue that the surprisingly narrow range (0.9–2.1 million) of these four autonomous estimates – derived from host-specificity relationships, ratios with other taxa, plant:beetle ratios, and a completely novel body-size approach – represents a major advance in honing in on the richness of this most significant taxon, and is thus of considerable importance to the debate on how many species exist.

“Using analogous approaches, we also produce independent estimates for all insects, mean: 5.5 million species (range 2.6–7.8 million), and for terrestrial arthropods, mean: 6.8 million species (range 5.9–7.8 million), which suggest that estimates for the world’s insects and their relatives are narrowing considerably.”

More bug progress: “How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth?” by Nigel E. Stork in the Annual Review of Entomology, January 2018.

“In the last decade, new methods of estimating global species richness have been developed and existing ones improved through the use of more appropriate statistical tools and new data. Taking the mean of most of these new estimates indicates that globally there are approximately 1.5 million, 5.5 million, and 7 million species of beetles, insects, and terrestrial arthropods, respectively. Previous estimates of 30 million species or more based on the host specificity of insects to plants now seem extremely unlikely. With 1 million insect species named, this suggests that 80% remain to be discovered …”

Frontiers of science


Related Links: 

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