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Evidence record

Is this a mass extinction?

Every sentence on the exploration belongs to at least one claim below. Each says what kind of statement it is, what it rests on, what the evidence does not establish, and how far it was checked. Nothing here is a score, and none of it is a verdict on a belief or a theory.

Last checked 24 September 2026.

  • A judgement, not a fact: 9
  • Source checked: 38
  • Partly checked: 8

If something here is wrong, misquoted, out of date or unfair, write to support@unknownoceans.com and give the claim number, which does not change.

What the question takes for granted

A scientific question with a definition inside it. Whether the present losses are a mass extinction depends on a threshold set from the fossil record, on how a modern rate is compared with a fossil one, and on how far the well-counted groups stand for the rest of life. The page reports the measurements and the argument over what they mean.

  • A mass extinction has an agreed definition

    Contested

    The usual line, the loss of more than three quarters of species in a geologically short interval, is widely used, and described by some who use it as arbitrary or heuristic.

  • A modern extinction rate can be compared with a background rate from fossils

    Contested

    Both sides of the present argument make the comparison and disagree over what it shows. The fossil record is mostly marine invertebrates, the modern record mostly land vertebrates.

  • Recorded losses are above the fossil background rate

    Established

    Accepted on both sides of the argument over the name: the dispute is over what the elevation means and where it is heading.

How the question is labelled

Claim: The rate, not the number

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s title and its stance: the recorded count of extinctions is small (claim 3), and the case for a sixth mass extinction rests on the rate (claims 5 and 7).

Other readings

Wiens and Saban argue that a rate above background does not by itself make a mass extinction (claim 42).

Claim 1 · checked 24 September 2026 · AI-assisted audit

Claim: Extinction now

Kind
Framing. Signposting. It asserts nothing a source could check.

The question

Claim: The number of species recorded as lost is small.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Small as a share of what has been assessed. The recorded count is a floor, and some researchers argue the true figure is far larger (claim 54).

Later work looked for

Crossref, 2023 on, "sixth mass extinction": Cowie, Bouchet and Fontaine 2025 give the 2024 Red List counts used here; nothing that changes the order of magnitude.

Claim 3 · checked 24 September 2026 · AI-assisted audit

Claim: The rate at which they are being lost is the part that matters

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s stance, following Ceballos and others 2015, who make the rate against background the test.

Other readings

Wiens and Saban argue that rates can exceed background outside mass extinctions, so the rate alone does not settle the question (claim 42).

Claim 4 · checked 24 September 2026 · AI-assisted audit

Claim: and it is not small

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Vertebrates only. Invertebrates and plants were not in that analysis.

Later work looked for

Crossref, 2016 on, "sixth mass extinction" and "extinction rates": Saban and Wiens 2025 report rates rising over five centuries and generally declining over the last hundred years; the page now reports that (claim 43).

Claim 5 · checked 24 September 2026 · AI-assisted audit

Claim: Documented extinctions since 1500 are far fewer than in the five great mass extinctions.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

Documented is the operative word: the count is a floor (claims 52 to 54).

Later work looked for

Crossref, 2023 on, "sixth mass extinction": both sides of the 2025 exchange agree the threshold has not been reached.

Claim 6 · checked 24 September 2026 · AI-assisted audit

Claim: Measured as a rate against the background from the fossil record, vertebrate losses over the last century are up to a hundred times higher,

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Accelerated modern human-induced species losses: Entering the sixth mass extinctionAbstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Observational study: associations, not causes

    The source reads: 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.

What this does not establish

Up to: the hundred is amphibians on the broader count. All vertebrates together came out at 22 to 53 times (claim 15).

Later work looked for

Crossref, 2016 on, "sixth mass extinction" and "extinction rates": Saban and Wiens 2025 report rates rising over five centuries and generally declining over the last hundred years; the page now reports that (claim 43).

Corrected

24 September 2026. Previously: “Measured as a rate against the background from the fossil record, current losses are up to a hundred times higher,” The figure is for vertebrates over the last century, as the paper says. "Current losses" read as all of life.

Claim 7 · checked 24 September 2026 · AI-assisted audit

Claim: and the comparison depends on assumptions that are stated openly and argued about.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Claim 8 · checked 24 September 2026 · AI-assisted audit

Claim: A mass extinction, as palaeontology defines it, is the loss of three quarters of species in a geologically short interval.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section II, Defining the Sixth Mass Extinction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: If one considers a mass extinction event as a short period when at least 75% of species are lost

  • Context

    Has the Earth’s sixth mass extinction already arrived?abstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so.

What this does not establish

The line is a convention, and some who use it call it arbitrary (claim 26).

Later work looked for

Crossref, 2023 on, "sixth mass extinction": the 2025 exchange uses the same 75 per cent line.

Claim 9 · checked 24 September 2026 · AI-assisted audit

Claim: By that definition this is not one yet.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2023 on, "sixth mass extinction": Wiens and Saban 2025 and Cowie, Bouchet and Fontaine 2025 both say the threshold has not been reached.

Claim 10 · checked 24 September 2026 · AI-assisted audit

Claim: The useful question is whether the present rate, continued, gets there, and how quickly.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s framing, which is the framing of Barnosky and others 2011 and Cowie and others 2022.

Other readings

Saban and Wiens caution against extrapolating recent extinctions into the future, finding that past extinctions did not strongly predict current risk (claim 43).

Claim 11 · checked 24 September 2026 · AI-assisted audit

What is measured

Claim: What is measured

Kind
Framing. Signposting. It asserts nothing a source could check.

The rate is far above background

Claim: The rate is far above background

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

For vertebrates, against a background measured for mammals.

Later work looked for

Crossref, 2016 on, "sixth mass extinction" and "extinction rates": Saban and Wiens 2025 report rates rising over five centuries and generally declining over the last hundred years; the page now reports that (claim 43).

Claim 13 · checked 24 September 2026 · AI-assisted audit

Claim: A 2015 study used a deliberately conservative background rate, two extinctions per 10,000 species per hundred years, twice the figure then in wide use, and counted only extinctions recorded on the IUCN Red List.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Accelerated modern human-induced species losses: Entering the sixth mass extinctionAbstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Observational study: associations, not causes

    The source reads: we use a recent estimate of a background rate of 2 mammal extinctions per 10,000 species per 100 years (that is, 2 E/MSY), which is twice as high as widely used previous estimates

  • Supports

    Accelerated modern human-induced species losses: Entering the sixth mass extinctionMaterials and Methods

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Observational study: associations, not causes

    The source reads: we compiled data on the total number of described species and the number of extinct and possibly extinct vertebrate species from the 2014 IUCN Red List

Later work looked for

How the method works; not a finding later work revises.

Corrected

24 September 2026. Previously: “and counted only extinctions the conservation registers have recorded.” Names the one register the study used.

Claim 14 · checked 24 September 2026 · AI-assisted audit

Claim: Even so, vertebrate losses since 1900 came out 22 times the background rate counting only species verified extinct, and 53 times counting those also listed as extinct in the wild or possibly extinct.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Accelerated modern human-induced species losses: Entering the sixth mass extinctionTable 2, Vertebrates row: highly conservative and conservative, since 1500 and since 1900

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Observational study: associations, not causes

    The source reads: Vertebrates 8 22 15 53

  • Supports

    Accelerated modern human-induced species losses: Entering the sixth mass extinctionTable 1 legend

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Research in animals · Observational study: associations, not causes

    The source reads: For the highly conservative rates, only species verified as “extinct” (EX) were included; for the conservative extinction rates, species in the categories “extinct in the wild” (EW) and “possibly extinct” (PE) were also included.

What this does not establish

Against a background of 2 per 10,000 species per century, measured for mammals and assumed for other vertebrates.

Later work looked for

Crossref, 2016 on, "sixth mass extinction" and "extinction rates": Saban and Wiens 2025 report rates rising over five centuries and generally declining over the last hundred years; the page now reports that (claim 43).

Claim 15 · checked 24 September 2026 · AI-assisted audit

Claim: Amphibians reach a hundred on the second count.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2016 on, "sixth mass extinction" and "extinction rates": Saban and Wiens 2025 report rates rising over five centuries and generally declining over the last hundred years; the page now reports that (claim 43).

Claim 16 · checked 24 September 2026 · AI-assisted audit

Claim: The authors’ point was that the conclusion survives every assumption chosen against it.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Accelerated modern human-induced species losses: Entering the sixth mass extinctionDiscussion

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Observational study: associations, not causes

    The source reads: Our analysis shows that current extinction rates vastly exceed natural average background rates, even when (i) the background rate is considered to be double previous estimates and when (ii) data on modern vertebrate extinctions are treated in the most conservative plausible way.

Claim 17 · checked 24 September 2026 · AI-assisted audit

Claim: How the comparison is made

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: 2 per 10,000

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

How the method works; not a finding later work revises.

Claim 19 · checked 24 September 2026 · AI-assisted audit

Claim: Background rate used

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: Species extinctions per species per hundred years.

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

How the method works; not a finding later work revises.

Claim 21 · checked 24 September 2026 · AI-assisted audit

Claim: Measured for mammals, applied to all vertebrates, and set at twice the figure then in wide use so the result is hard to dismiss.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

How the method works; not a finding later work revises.

Claim 22 · checked 24 September 2026 · AI-assisted audit

Claim: 75%

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section II, Defining the Sixth Mass Extinction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: If one considers a mass extinction event as a short period when at least 75% of species are lost

Later work looked for

Crossref, 2023 on, "sixth mass extinction": the same line is used on both sides of the 2025 exchange.

Claim 23 · checked 24 September 2026 · AI-assisted audit

Claim: The threshold for a mass extinction

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section II, Defining the Sixth Mass Extinction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: If one considers a mass extinction event as a short period when at least 75% of species are lost

What this does not establish

A convention (claim 26).

Later work looked for

Crossref, 2023 on, "sixth mass extinction": unchanged.

Claim 24 · checked 24 September 2026 · AI-assisted audit

Claim: Species lost in a geologically short interval.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section II, Defining the Sixth Mass Extinction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: If one considers a mass extinction event as a short period when at least 75% of species are lost

  • Context

    Has the Earth’s sixth mass extinction already arrived?abstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026

    The source reads: Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so.

Later work looked for

Crossref, 2023 on, "sixth mass extinction": unchanged.

Corrected

24 September 2026. Previously: “Species lost in a geologically short interval, usually taken as under two million years.” The two-million-year figure is in the body of Barnosky and others 2011, which could not be read, and no readable source gave it.

Claim 25 · checked 24 September 2026 · AI-assisted audit

Claim: The line is a convention, which some who use it call arbitrary.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Corrected

24 September 2026. Previously: “” Added: the researchers who use the threshold describe it as arbitrary or heuristic, and a reader should know that.

Claim 26 · checked 24 September 2026 · AI-assisted audit

Claim: The end-Permian is often put at 90 to 96 per cent of marine species; a 2016 re-analysis puts it near 81.

Kind
Disputed. A contested point, where the page reports a side or the disagreement.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Estimates of the magnitudes of major marine mass extinctions in earth historyabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Measurement

    The source reads: They indicate that only ∼81% of marine species died out in the great terminal Permian crisis, whereas levels of 90–96% have frequently been quoted in the literature.

What this does not establish

Read as the abstract and significance statement only. The re-analysis is one author’s; the page reports it beside the older figure rather than replacing it.

Later work looked for

Crossref, 2017 on, "end-Permian mass extinction magnitude": no newer estimate found that supersedes it.

Corrected

24 September 2026. Previously: “The five previous events reached between 75 and 96 per cent.” The per-event range is in the body of Barnosky and others 2011, which could not be read. The top of the range is contested: Stanley 2016 re-estimates the end-Permian at about 81 per cent.

Claim 27 · checked 24 September 2026 · AI-assisted audit

Claim: 22 to 53x

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2016 on, "sixth mass extinction" and "extinction rates": Saban and Wiens 2025 report rates rising over five centuries and generally declining over the last hundred years; the page now reports that (claim 43).

Claim 28 · checked 24 September 2026 · AI-assisted audit

Claim: Vertebrate rate since 1900, against background

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: The low figure counts only species verified extinct, the high one adds those extinct in the wild or possibly extinct.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    Accelerated modern human-induced species losses: Entering the sixth mass extinctionTable 1 legend

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Observational study: associations, not causes

    The source reads: For the highly conservative rates, only species verified as “extinct” (EX) were included; for the conservative extinction rates, species in the categories “extinct in the wild” (EW) and “possibly extinct” (PE) were also included.

Later work looked for

How the method works; not a finding later work revises.

Claim 30 · checked 24 September 2026 · AI-assisted audit

Claim: Amphibians alone reach a hundred.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

On the broader count only.

Later work looked for

Crossref, 2016 on, "sixth mass extinction" and "extinction rates": Saban and Wiens 2025 report rates rising over five centuries and generally declining over the last hundred years; the page now reports that (claim 43).

Claim 31 · checked 24 September 2026 · AI-assisted audit

The comparison is harder than it looks

Claim: The comparison is harder than it looks

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

A heading for claims 33 to 44.

Claim 32 · checked 24 September 2026 · AI-assisted audit

Claim: The five earlier events are measured mostly from the fossils of marine invertebrates.

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section I, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: the previous events were mostly defined based on marine, largely invertebrate, fossils

Later work looked for

Crossref, 2023 on, "sixth mass extinction": Cowie, Bouchet and Fontaine 2025 repeat it.

Corrected

24 September 2026. Previously: “The fossil record preserves hard-bodied, widespread, marine species well and everything else poorly.” Narrowed to what a readable review says. "Widespread" and the general claim about the fossil record rested on the closed body of Barnosky and others 2011.

Claim 33 · checked 24 September 2026 · AI-assisted audit

Claim: Shells and bones last; most other animals vanish without trace.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?Summary

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: molluscs have significant advantages among invertebrates because of their shells, which remain after death as a permanent record, while most other invertebrates vanish without trace

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section III

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: For vertebrates, the bones of which may be preserved long after a species went extinct, knowledge of such species is more complete

What this does not establish

A general statement; the review notes a real body of work on fossil insects.

Claim 34 · checked 24 September 2026 · AI-assisted audit

Claim: Modern assessment runs the other way: the Red List has evaluated almost every described bird and mammal and only a minute fraction of invertebrates,

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?Abstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: the Red List is heavily biased: almost all birds and mammals but only a minute fraction of invertebrates have been evaluated against conservation criteria

  • Context

    Accelerated modern human-induced species losses: Entering the sixth mass extinctionTable 1

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: Mammals 77 35 111 69 100% (5,513) Birds 140 57 163 80 100% (10,425) Reptiles 21 8 37 24 44% (4,414)

    The 2014 figures the page used before: every described mammal and bird then evaluated.

Later work looked for

Crossref, 2020 on, "IUCN Red List" coverage: the 2020 Red List had evaluated all birds and 91 per cent of mammals (Cowie and others 2022); the 2014 reptile and fish percentages the page printed were out of date and are gone.

Corrected

24 September 2026. Previously: “Modern assessment runs the other way: every described mammal and bird has been evaluated, against 44 per cent of reptiles and 38 per cent of fishes.” The percentages were the 2014 Red List, printed in the present tense; by 2020 91 per cent of mammals were evaluated as more were described. The contrast that matters for the fossil comparison is vertebrates against invertebrates, which the 2022 review states.

Claim 35 · checked 24 September 2026 · AI-assisted audit

Claim: and the present wave of losses is largely on land and in fresh water.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2023 on: Saban and Wiens 2025 find most non-island extinctions were in fresh water, consistent with it.

Claim 36 · checked 24 September 2026 · AI-assisted audit

Claim: The two datasets are not samples of the same thing.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from claims 33 to 36: one record is mostly marine invertebrates, the other mostly land vertebrates.

Claim 37 · checked 24 September 2026 · AI-assisted audit

Claim: A 2011 analysis worked through those biases.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Has the Earth’s sixth mass extinction already arrived?abstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Texts · Review of the field

    The source reads: Here we review how differences between fossil and modern data and the addition of recently available palaeontological information influence our understanding of the current extinction crisis.

What this does not establish

Read as its abstract; the body is closed.

Claim 38 · checked 24 September 2026 · AI-assisted audit

Claim: Palaeontologists count a mass extinction as the loss of more than three quarters of species in a geologically short interval, which has happened five times in 540 million years,

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Has the Earth’s sixth mass extinction already arrived?abstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section I, Introduction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: with most authors accepting five substantial mass extinctions since the Cambrian

What this does not establish

Barnosky read as its abstract. The count of five is the common one; the 2022 review notes that some authors count as few as two or as many as 61.

Later work looked for

Crossref, 2023 on, "sixth mass extinction": unchanged.

Claim 39 · checked 24 September 2026 · AI-assisted audit

Claim: and the losses so far are well short of that while the rates are elevated.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Has the Earth’s sixth mass extinction already arrived?abstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Earth and its record · Review of the field

    The source reads: Our results confirm that current extinction rates are higher than would be expected from the fossil record

  • Supports

    Has the Earth’s sixth mass extinction already arrived?Nature editorial summary

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026

    The source reads: conclude that the recent loss of species is dramatic and serious, but not yet in the mass extinction category

What this does not establish

The abstract and the journal’s summary were read, not the paper’s body.

Claim 40 · checked 24 September 2026 · AI-assisted audit

Claim: Whether an elevated rate makes a mass extinction is itself argued.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2023 on, "sixth mass extinction": the 2025 exchange in Trends in Ecology and Evolution (Wiens and Saban; Cowie, Bouchet and Fontaine; a further reply by Wiens and Saban, read only as a record) is the newest; page updated to report it.

Corrected

24 September 2026. Previously: “” Added with claims 42 to 44: the page did not report the 2025 critique of the rate argument or the reply to it.

Claim 41 · checked 24 September 2026 · AI-assisted audit

Claim: John Wiens and Kristen Saban argued in 2025 that extinction rates can exceed background outside mass extinctions and that recent losses were mostly of island species,

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Questioning the sixth mass extinctionabstract

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026 · Texts · Review of the field

    The source reads: Some studies showed that recent extinction rates are faster than fossil background rates, but extinction rates can exceed background rates outside mass extinctions. Other studies extrapolated from recent extinctions to project 75% global species loss. But these recent extinctions were mostly of island species.

What this does not establish

Read as the abstract; the full paper was refused by the publisher here.

Later work looked for

Crossref, 2023 on, "sixth mass extinction": the 2025 exchange in Trends in Ecology and Evolution (Wiens and Saban; Cowie, Bouchet and Fontaine; a further reply by Wiens and Saban, read only as a record) is the newest; page updated to report it.

Corrected

24 September 2026. Previously: “” Added: the main published critique of the rate argument.

Claim 42 · checked 24 September 2026 · AI-assisted audit

Claim: and their own count found rates rising across five centuries but generally falling over the last hundred years.

Kind
Observation. Something measured or seen, as the named source reports it.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Read as the abstract. It covers recorded extinctions in plants and animals, and its authors caution against extrapolating them.

Other readings

Ceballos and others 2015 found vertebrate rates since 1900 higher than since 1500 (Table 2). The two analyses count different groups over different spans.

Later work looked for

Crossref, 2025 on, "extinction rates" and "sixth mass extinction": nothing later found.

Corrected

24 September 2026. Previously: “” Added: a newer analysis of recorded extinctions that bears on the trend.

Claim 43 · checked 24 September 2026 · AI-assisted audit

Claim: Robert Cowie, Philippe Bouchet and Benoît Fontaine replied that figures like these rest largely on vertebrates and plants, which are far better known than the rest of life and not representative of it.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2023 on, "sixth mass extinction": the 2025 exchange in Trends in Ecology and Evolution (Wiens and Saban; Cowie, Bouchet and Fontaine; a further reply by Wiens and Saban, read only as a record) is the newest; page updated to report it.

Corrected

24 September 2026. Previously: “” Added: the published reply, so both sides are named.

Claim 44 · checked 24 September 2026 · AI-assisted audit

What is not counted

Claim: What is not counted

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: A species can be declared extinct decades after the last one dies

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section III.2

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: the last reliable sighting dating from 1963 ... However, Butchart et al. (2018) recommended that it remain evaluated as Critically Endangered (Possibly Extinct)

    The Eskimo curlew, which the review reports was still assessed as Critically Endangered (Possibly Extinct) after a 2018 re-evaluation.

Later work looked for

How the method works; not a finding later work revises.

Corrected

24 September 2026. Previously: “A species is declared extinct decades after the last one dies” Not every declaration takes decades; the source shows that some do.

Claim 46 · checked 24 September 2026 · AI-assisted audit

Claim: which makes every count a floor

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Follows from the listing rules and the delay (claims 46 and 49), which the 2022 review draws the same conclusion from.

Claim 47 · checked 24 September 2026 · AI-assisted audit

How much is already lost

Claim: How much is already lost

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: A species is declared extinct only after exhaustive searches fail, which can take decades.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section III.2, quoting the IUCN guidelines

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: Listing of a species as Extinct requires that exhaustive surveys have been undertaken in all known or likely habitat throughout its historic range

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section III.2

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: the last reliable sighting dating from 1963 ... However, Butchart et al. (2018) recommended that it remain evaluated as Critically Endangered (Possibly Extinct)

Later work looked for

How the method works; not a finding later work revises.

Corrected

24 September 2026. Previously: “A species is declared extinct only after searches fail, which takes decades.” The IUCN rule asks for exhaustive surveys; the delay is decades in the examples the review gives, not in every case.

Claim 49 · checked 24 September 2026 · AI-assisted audit

Claim: Most described species have never been assessed,

Kind
Present-day figure. A count, survey or report finding, as the named source gives it.
Review
Source checked. The cited passage was read, and it says this.

Later work looked for

Crossref, 2023 on: the 2024 Red List counts in Cowie, Bouchet and Fontaine 2025 are the newest found; the 2022 review gives 5.6 per cent for 2020.

Claim 50 · checked 24 September 2026 · AI-assisted audit

Claim: and on the estimate now treated as the default, most species have never been described at all.

Kind
What a model says. What a theory or model predicts or describes, which is not the same as what has been observed.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    How Many Species Are There on Earth and in the Ocean?Abstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Model

    The source reads: our results suggest that some 86% of existing species on Earth and 91% of species in the ocean still await description

  • Supports

    How many species are there on Earth? Progress and problemssecond paragraph

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026

    The source reads: This paper has since become the “default” estimate of the number of living species on the plant (8.75 million), even though approximately 80% of those species are hypothetical.

What this does not establish

An estimate from a model of how higher taxa accumulate. Estimates of the total have ranged from about 2 million to trillions.

Other readings

Wiens 2023 reviews estimates from 2 million to 3 trillion; the page’s question on unnamed species covers them.

Corrected

24 September 2026. Previously: “and most species have never been described at all.” The share of undescribed species is an estimate, not a count, and is attributed as one.

24 September 2026. Previously: “and on the most cited estimate most species have never been described at all.” No source read counts citations. Wiens 2023 calls Mora and others 2011 the “default” estimate, and the sentence now says that.

Claim 51 · checked 24 September 2026 · AI-assisted audit

Claim: So the documented count is a floor by construction,

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Claim 52 · checked 24 September 2026 · AI-assisted audit

Claim: and estimates of the true figure depend on extrapolating from the groups that are well studied to the invertebrates and plants that are not.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?Abstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: Incorporating estimates of the true number of invertebrate extinctions leads to the conclusion that the rate vastly exceeds the background rate

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?Abstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: Plants face similar conservation biases as do invertebrates

Claim 53 · checked 24 September 2026 · AI-assisted audit

Claim: One such extrapolation, from a random sample of land snails, puts losses since 1500 at 7.5 to 13 per cent of all known species, against well under one per cent on the Red List;

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

What this does not establish

An extrapolation from one group to all of life. Saban and Wiens find recorded extinctions most frequent among molluscs, which would make snails a high rather than a typical case.

Later work looked for

Crossref, 2023 on, "sixth mass extinction": the 2025 exchange in Trends in Ecology and Evolution (Wiens and Saban; Cowie, Bouchet and Fontaine; a further reply by Wiens and Saban, read only as a record) is the newest; page updated to report it.

Corrected

24 September 2026. Previously: “” Added: the page said estimates depend on extrapolation without giving one.

Claim 54 · checked 24 September 2026 · AI-assisted audit

Claim: its authors call it bold.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

Claim 55 · checked 24 September 2026 · AI-assisted audit

Whether the trajectory continues

Claim: Whether the trajectory continues

Kind
Framing. Signposting. It asserts nothing a source could check.

Claim: Nature’s summary of the 2011 analysis put the direction plainly: the loss of the species now classed as critically endangered “would soon propel the world into its sixth mass extinction”.

Kind
Quotes a source. The words of a named text, checked against the source.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

  • Supports

    Has the Earth’s sixth mass extinction already arrived?Nature editorial summary, "Mass extinctions: are we there yet?"

    Cited · Link answered, 19 October 2026 · Abstract only, 24 September 2026

    The source reads: there are clear indications that the loss of species now classed as 'critically endangered' would soon propel the world into its sixth mass extinction

What this does not establish

The words are the journal’s editorial summary of the paper, read in full; the paper’s body, where the argument is made, was not read.

Corrected

24 September 2026. Previously: “The 2011 analysis put the direction plainly: the loss of the species now classed as critically endangered “would soon propel the world into its sixth mass extinction”.” The quoted words are Nature’s editorial summary, not the authors’ abstract, and are now attributed to it.

Claim 57 · checked 24 September 2026 · AI-assisted audit

Claim: A 2022 review, citing that analysis, says a mass extinction could arrive within one or a few centuries if nothing slows the loss.

Kind
What scholars argue. A report of what specialists argue, or where they disagree.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?section II, Defining the Sixth Mass Extinction

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: Indeed it could happen within just one or a few centuries if nothing is done to slow or stop the current rate of biodiversity loss

What this does not establish

A projection, not an observation, and reported at second hand: the 2011 paper’s own figures were not read.

Later work looked for

Crossref, 2023 on, "sixth mass extinction": the 2025 exchange in Trends in Ecology and Evolution (Wiens and Saban; Cowie, Bouchet and Fontaine; a further reply by Wiens and Saban, read only as a record) is the newest; page updated to report it.

Corrected

24 September 2026. Previously: “The year figures behind that sentence are in the paper’s body, which is closed, so this page does not print them.” A readable review reports the timescale, so the page gives it, attributed.

Claim 58 · checked 24 September 2026 · AI-assisted audit

Claim: The five previous events all had natural causes,

Kind
What the field holds. The settled view of a field, as a review, a consensus statement or a reference work gives it. Not one study.
Review
Source checked. The cited passage was read, and it says this.

  • Supports

    The Sixth Mass Extinction: fact, fiction or speculation?Abstract

    Cited · Link answered, 19 October 2026 · Read in full, 24 September 2026 · Texts · Review of the field

    The source reads: There have been five Mass Extinction events in the history of Earth's biodiversity, all caused by dramatic but natural phenomena.

Later work looked for

Crossref, 2015 on, Devonian causes: work continues on which natural causes, none changes that they were natural.

Corrected

24 September 2026. Previously: “The causes of the five previous events were mostly indifferent to what was alive,” States the sourced part first.

Claim 59 · checked 24 September 2026 · AI-assisted audit

Claim: mostly indifferent to what was alive, though not wholly:

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s gloss: the causes named for the five are physical events, with the Devonian hypothesis as an exception (claim 61).

Claim 60 · checked 24 September 2026 · AI-assisted audit

Claim: one hypothesis ties the Devonian crisis in part to land plants spreading, enriching the seas and drawing carbon dioxide down.

Kind
Hypothesis. A proposed explanation, not an established one.
Review
Partly checked. Only part of the source could be read. What was not read is listed.

What this does not establish

Read as the abstract. Its authors call it a model that needs further testing, and the role of anoxia in the Late Devonian is still argued.

Later work looked for

Crossref, 2015 on, "Devonian land plants weathering extinction anoxia": work continues on both sides, including a 2026 paper re-thinking anoxia as the cause; the page states it as a hypothesis.

Corrected

24 September 2026. Previously: “the Devonian is tied in part to land plants spreading and pulling carbon dioxide down.” A hypothesis stated as a finding, with no source. Now attributed as a hypothesis and cited to Algeo and Scheckler 1998.

Claim 61 · checked 24 September 2026 · AI-assisted audit

Claim: This one has a cause that can in principle stop.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

Both papers make this point about human causes.

Claim 62 · checked 24 September 2026 · AI-assisted audit

Claim: That is a genuine difference and not a reassurance: it means the outcome depends on decisions rather than on physics, which makes it unpredictable in a different way.

Kind
This page’s reading. A judgement the page makes from the evidence. Others read it differently.
Review
A judgement, not a fact. Reviewed for whether it is fairly put and follows from the checked claims. No source can confirm it.

The page’s own reading of claim 62.

Claim 63 · checked 24 September 2026 · AI-assisted audit

What was read