The Species Black List

Extinction, Then and Now

Over the last 500 years, mammals have disappeared faster than at any time in the 126,000 years before, including the great die-off of the Ice Age megafauna that took the mammoths and the giant ground sloths.

That works out to about one mammal species lost every 7 or 8 years since 1500, against one every 50 years at the prehistoric peak, 10,000 to 8,000 years ago. Fossils miss small animals, so the prehistoric rates are minimums and the real gap is somewhat smaller than 7x.

Fifty Thousand Years of Losses

Why does the rate jump when it does? North America lost most of its dated species between 15,000 and 8,000 years ago, soon after people arrived, and Madagascar lost most of its within the last 4,000 years, after people reached the island. When Andermann and colleagues tested the whole record, human population size predicted these extinctions with 96% accuracy, and past climate did no better than chance.

A last record is not an extinction date. The last fossil of a species is the last animal anyone has found, so each species outlived its record, sometimes by thousands of years.

How Do You Weigh a Lost Species?

Counting species treats a lost shrew and the last of an entire order of hoofed mammals alike. Evolutionary history does not. It is the length of the branches of the mammal family tree that only the lost species carried, measured in millions of years, and since the Late Pleistocene, about 130,000 years ago, the world has lost about 2.7 billion years of it. That is more than half the age of the Earth.

Before 1500, the largest losses of evolutionary history were in Eurasia, South America and North America, between 760 and 984 million years each. As a share of what a region had, the Caribbean lost the most, 10.6%, followed by North America at 8.2%; the world as a whole lost 5.0%, and Africa the least, 1.6%.

Since 1500 the order changes. The Caribbean has lost 507 million years, more than in all of its prehistory, among them island shrews, hutias and rice rats. Madagascar has lost 115 million years and Sahul 114 million, about 40% of Sahul's prehistoric total, with the thylacine (Thylacinus cynocephalus) among its 24 species.

Birds fall outside the mammal atlas. Cooke and colleagues estimate that at least 1,300 to 1,500 bird species have been lost since the Late Pleistocene, 61% of them in the Pacific, and describe a wave around 1300 CE as likely the largest extinction wave of vertebrates that people have caused.

Is Extinction Slowing Down?

Count the species declared extinct by the decade they were last seen, and extinction seems to have peaked in the 1970s and eased since. Saban and Wiens read the record that way across plants and animals in 2025. But declaring a species extinct takes years of searches that find nothing, so the most recent decades are still filling in.

Easing is not the same as small. Even before any correction, the Red List holds 36 to 78 amphibians, reptiles, birds and mammals declared or flagged as possibly extinct for each decade from the 1960s to the 2000s, more than in any decade from the 1900s to the 1950s (13 to 25). These animals are still being lost decade after decade, and once the lag is allowed for, the easing disappears.

A vertebrate is flagged as possibly extinct a median 17 years after it was last seen, and only about half of the flagged amphibians, reptiles, birds and mammals are declared extinct within 60 years of their last sighting. Allow for that lag and the decline disappears. The count climbed, then held: about 60 species per decade for those last seen in the 1980s, 1990s and 2000s (45 to 80), against about 17 per decade early in the twentieth century.

Species found again are not counted. Ten vertebrates still flagged in the 2024 data have since been reported alive, among them the Fernandina giant tortoise (Chelonoidis phantasticus) and De Winton's golden mole (Cryptochloris wintoni), and they are left out. The expected final count also allows for more to turn up. Of the 173 amphibians, reptiles, birds and mammals the Red List flagged as possibly extinct and has since reassessed, 46 had been found alive, and the count assumes the same share of today's flagged species will be found. Species already declared extinct turn up far less often, 5% of those reassessed.

Fishes add about 40 per decade (25 to 55), most of the 1980s from the cichlids of Lake Victoria. The 2010s are too recent to read, since most of their losses will not be flagged before the 2030s.

The line forward assumes no new disease wave and no step change in climate. Nearly all the amphibians in the 1980s to 2000s count, 123 of 133, have Red List assessments that name chytrid, the fungal disease that swept through them, so the line leaves that wave out and holds every other group to its 1980s to 2000s rate. On that line, 2020 to 2100 would add about 150 more amphibians, reptiles, birds and mammals (120 to 200), on top of those lost since 1500, and about 220 fishes, leaving out the collapse of Lake Victoria's cichlids.

A single event can change that. The amphibians whose assessments name chytrid add up to about 170 expected extinctions, so one more wave like it would roughly double the line, to about 320. At chytrid's pace all century it would be about 480. The fishes flagged after Lake Victoria's collapse, which followed the introduction of the Nile perch, add up to about 45, and one more collapse like it would take the fish line to about 265. These are straight lines, not forecasts.

The Running Total

Counting only the species on record, more than 1,200 amphibians, reptiles, birds and mammals have been lost in the last 50,000 years, as people spread across Eurasia, Australia and New Guinea and then the rest of the world. Since 1500 the expected total is about 580 (490 to 680), along with about 270 fishes. On the line forward, the total since 1500 would reach about 730 by 2100.

Lost Is Not Gone

About a third of the tetrapods ever listed as lost have turned up again: 424 of the 1,280 that Lindken and colleagues followed. Rediscoveries climbed for forty years to a peak of 150 in the 2000s. The count for the 2010s was gathered in 2020, so it is still filling in as well.

The finds keep coming, in many languages. Across the scientific literature in 15 languages, 95 papers reported a species found alive after being lost in 2020 to 2026, against 72 in all of 2010 to 2019. Another 156 reported a species found again in a country or region where it had been lost. After English, most of these were published in Spanish, German, French and Portuguese. A search like this finds a minimum, not a total. Lindken and colleagues also found that the species people went looking for were the ones most likely to be found.

Of the 2,016 species on our lost list, 1,395 have never been flagged as possibly extinct. Each one is a search that could end with a photograph.

Browse the lost species Help look for them