Note by Kip Hansen — 22 February 2024 — 1600 words/8 minutes
We are constantly bombarded by news about “species” – Endangered Species, Threatened Species, Vanishing Species, Loss of Species such as “Researchers estimate that the current rate of species loss varies between 100 and 10,000 times the background extinction rate” [ source: Britannica Feb 15, 2024 ]. Let me clarify that: Britannica says that the Earth is losing species at a rate of 100 to 50,000 species per year.
How can such an impossibly wide range even be considered an “estimate”? Easy! There is no agreed upon scientific definition of what a species is – so there can be no count either of existing species nor of species loss or extinction, in the present or in the past.
There are ‘equally good’ estimates of the number of existing species: 8.7 million. “That is a new, estimated total number of species on Earth—the most precise calculation ever offered—with 6.5 million species found on land and 2.2 million dwelling in the ocean depths.” [ source ]
or
“As of 2021, we have identified and describedapproximately 2.13 million species.“ “Estimates suggest that around 20% of described species may be undiscovered synonyms [the same species under a different name]. Adjusting for this, the actual number of described species might be closer to 1.7 million.” Taking into account estimates of undiscovered or undescribed species: “The true number of species remains elusive. Estimates vary widely: 5 to 10 million eukaryotes (excluding viruses and bacteria). Numbers exceeding 100 million or as low as 3 million.” [ source ]
So, here’s the summary of exert knowledge:
Number of Species
8.7 million or maybe 2.13 million or maybe 1.7 million or maybe 100 million or maybe 3 million.
Of which we are reportedly losing between 100 to 50,000 per year.
Carl Zimmer, science writer for the New York Times, gives another view of the species issue in a recent piece “What Is a Species, Anyway? — Some of the best known species on Earth may not be what they seem”.
He touches on the number-of-species issue giving: “So far, researchers have named about 2.3 million species, but there are millions — perhaps even billions — left to be discovered.” So, to the above summary we might have to add “or maybe billions.”
Zimmer goes on to explain:
“As if this quest isn’t hard enough, biologists cannot agree on what a species is. A 2021 survey found that practicing biologists used 16 different approaches to categorizing species. Any two of the scientists picked at random were overwhelmingly likely to use different ones.
“Everyone uses the term, but no one knows what it is,” said Michal Grabowski, a biologist at the University of Lodz in Poland.
The debate over species is more than an academic pastime. In the current extinction crisis, scientists urgently need to take stock of the world’s biological diversity.” [ NY Times as above ]
[Note: I have touched on the species problem several times here at WUWT: for instance “The Gray, Gray World of Wolves” and “Darwin — We’ve Got a Problem” ]

Zimmer is not kidding about the 16 major categories of opinions that biologists hold about the definition of what constitutes a species. In Current Biology, Sean Stankowski and Mark Ravinet, wrote “Quantifying the use of species concepts” in which they describe the “species problem” this way:
“Dozens of species concepts are currently recognized, but we lack a concrete understanding of how much researchers actually disagree and the factors that cause them to think differently. To address this, we used a survey to quantify the species problem for the first time. The results indicate that the disagreement is extensive: two randomly chosen respondents will most likely disagree on the nature of species.”
Here is their chart (see the .pdf file for a better look):

Why do we even think about “what is a species?” As we started out, the world is agog about species, loss of, discovery of, rediscovery of and extinction of.
Governments, national and international, have been passing laws and signing treaties dealing with the protection of species deemed threatened by or endangered by extinction. These treaties and laws require governments to protect and save these species.
How can we determine what to save if we don’t even know what we are talking about?
In the United States, we have the famous (or infamous, opinions vary) Endangered Species Act (ESA). It is available, in all its glory, in a .pdf file available here. Hey, there’s a law and any lawyer (even a poor one) will tell you that laws are required to have clear-cut definitions of terms used in that law – least they be deemed “ambiguous” and in danger of being invalidated by the courts.
So, surely, the ESA defines species, right? Let’s see…. Section 3. Definitions — that should have it. Here are the pertinent points of Section 3:
(16) The term “species” includes any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature.
(6) The term “endangered species” means any species which is in danger of extinction throughout all or a significant portion of its range other than a species of the Class Insecta determined by the Secretary to constitute a pest whose protection under the provisions of this Act would present an overwhelming and overriding risk to man.
(20) The term “threatened species” means any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range.
Wait a minute! Surely there is a definition of “species” other than the fact that it is meant include “any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature.” We get a fine definition of “a subspecies or a distinct population” but not the primary definition of a species.
Does it matter? Don’t all those taxonomists and biologists agree, at least generally, that a species is a population “which interbreeds when mature.”
Nope again, that is just the high-school version (ask any A-non-I chat) of what it a species is. And, in the eyes of biologists, it only includes two of the 16 major divisions of species concepts according to Stankowski and Ravinet :
Biological Species Concept I (BSCI) (Mayr 1942, 1995) Species are a group of interbreeding natural populations that are reproductively isolated from other such groups
Biological Species Concept II (BSCII) (Coyne & Orr 2004) Species are groups of interbreeding natural populations that are substantially but not necessarily completely reproductively isolated from other such groups
Note that it does not include the basic Darwinian definition, which is:
Darwinian Species Concept (DSC) (Jolly 2014) A species is an evolutionary lineage, or lineage segment, that is phenotypically distinguishable from all other such units and is usefully distinguished in scientific discourse.
There are 13 others, found in Stankowski’s Supplemental Materials, for those wishing to disappear down the species rabbit hole.
I suggest reading Carl Zimmer’s piece in the NY Times (this link should be good even if you don’t subscribe to the Times) to see what all the fuss is about. The Mass Extinction types are worried about what will happen if they spend their time trying to figure out what a species really is:
“Thomas Wells, a botanist at the University of Oxford, is concerned that debates about the nature of species are slowing down the work of discovering new ones. Taxonomy is traditionally a slow process, especially for plants. It can take decades for a new species of plant to be formally named in a scientific publication after it is first discovered. That sluggish pace is unacceptable, he said, when three out of four undescribed species of plants are already threatened with extinction.” [ from NY Times – Zimmer ]
How Wells can know, absent a solid working definition of “species” how many of the millions, or perhaps billions, of not-yet discovered and not-yet described “somethings we might decide to call species” are “already threatened with extinction” is a mystery to me. I might even call that opinion unscientific.
Accounts of the misuse of the U.S.’s ESA are widely known – like protecting the Red Wolf which is a hybrid of the Gray Wolf and Coyote as a “species” by breeding captured animals that appeared to be Red Wolves to supplement the existing but shrinking population, rejecting those with too much wolf or too much coyote genes. This has been going on for 50 years. More importantly, the ESA is widely used by radical environmental groups to block development projects (like pipelines) to which they object for other unrelated reasons (see the Prebles Meadow Jumping Mouse). Readers can supply local examples.
Bottom Lines:
1. The “Species Problem” is still going strong and is unlikely to be resolved anytime soon.
2. That means that there will be those who take advantage of the ambiguity of species definitions to use the Endangered Species Act – ESA – (in the U.S.) and its international counterparts to forward other agendas.
3. The U.S. ESA is intentionally so broad that it could be conceivably be stretched to demanding protection of anthropogenically created sub-populations of rare animals and plants.
4. We need pragmatic reform of the U.S. ESA and re-evaluation of international treaties concerning endangered animals and plants.
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Author’s Comment:
We have had good coverage here at WUWT of the species problem and the so-called 6th Mass Extinction event from several authors including the Willis and Jim Steele.
Dr. Susan Crockford covered the Polar Bear portion of the Zimmer/NY Times article at “NY Times pushes an implausible story of polar bear evolution and what makes a species” which has just been re-posted here.
The Endangered Species Act is a well-meaning but poorly written and perversely implemented piece of legislation and is desperate for reform. It lacks any boundaries for biological significance and pragmatic application.
Specious means: “superficially plausible, but actually wrong.”
Thanks for reading.
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This is more of “a question” than a comment.
What is a “species” was determined based on physical differences, behavior, reproducibility, etc.; long before Man knew anything about “DNA”.
A male St. Bernard would likely have difficulty mating with a female Chihuahua, and vise/versa.
If we, today, knew nothing of either but just found fossil remains, what would be concluded?
Honestly, based on strictly examinations of the bones …
So why do they consider, say, a Suwannee Bass to be a different “species” than another type of largemouth bass? (*Or maybe even a smallmouth bass?)
I remember reading about a cross between a smallmouth and largemouth bass. It earned the name of a “Mean-mouth” bass for it’s aggressive tendencies leading it to nip at the the legs of swimmers where it was stocked.
Gunga ==> and that is precisely “The Species Problem”.
Standard practice of eco-activists is to slice and dice on geographic and political boundaries that creatures cannot understand, until finding a population small enough to claim it is threatened with extinction.
So bad/rotten that some claim every river has a different species of salmon (never mind they will move to a different river if water temperature suggests it is too shallow upstream).
Don’t forget the “Scioto Madtom”. Lot’s of other “madtoms” in other rivers.
Examine the human differences, are redhead of blonds or … skin tones something “different” than the rest of us? Based on only the Theory of Evolution, some twisted it to mean that, somehow, skin tone meant that those with darker tones were “less evolved”.
A Theory gone very wrong.
Anyone trained in biology would know that there are a variety of differences that can determine one species from another. Two major points, besides physical difference are: Genetic differences can preclude interbreeding (an easy one) or behavioral differences may prevent interbreeding (but could be produced artificially). A ring of mosquito population around the Mediterranean can interbreed but the two populations facing each other across the Strait of Gibraltar cannot (are they different species?). The same is true for some bird populations across Asia.
This brings us to the lumpers and the splitters in species studies. This argument has been going for decades and cannot be ordained away by anyone. There are no defining rules in such a subjective topic. Let it go and relax.
Finally, the claim of all the species loss is produced from tortured computer programs that produce tortured results. One is a program for determining how many species might be in a square meter of jungle (used in species studies). They then ran the program backwards, which could not predict how many species would be there, which they interpreted a species loss, huge losses. The real program starts with a full species list and works downward.
In another laughable computer program, they asked how many species might be lost before we ever identified them—it’s like they never existed. For this, you can put in any numbers you want and pretend they are real, just as they do at the EPA when guessimating the toxicity of a substance for which no studies have been made–doughnut and coffee calculations that are meaningless.