Extinction crisis puts 1 million species on the brink

When an animal species is lost, an entire set of traits disappears with it – genes, behaviours, activities and interactions with other plants and animals that may have taken thousands or millions – even billions – of years to develop.

Whatever role that species played in an ecosystem is also lost, whether it is pollinating certain plants, pumping nutrients into soil, fertilizing forests or keeping other animal populations in check. If that function was crucial to the health of an ecosystem, the animals’ disappearance could transform a landscape.

Lose too many species and the results can be catastrophic, leading to the collapse of an entire system.

GONE FOREVER

In the past five centuries, hundreds of unique animals have disappeared around the world, such as the flightless Dodo bird that was killed off the island of Mauritius in the late 1600s.

In many cases, humans have been blamed – first through fishing or hunting, as was the case with South Africa’s zebra subspecies Quagga, which was hunted to its death in the late 19th century – and more recently through activities that pollute wild habitats, disrupt or take over.

Before a species goes extinct, it can already be considered “functionally extinct” – with not enough individuals left to ensure that the species survives. More recent extinctions have allowed humans to interact with some species’ last known individuals, known as “finalists”. When they go, it’s the end of those evolutionary lines – as happened in these iconic cases:

* “Toughie” was the last known individual of the Rabb’s Fringe-Limbed tree frog. All but a few dozen of its species have been wiped out in the wild in Panama by chytrid fungus. In his enclosure at the Atlanta Botanical Garden, he called out in vain for a mate who did not exist. He died in 2016.

* The story of passenger pigeon “Martha” is a cautionary tale for conservation: in the 1850s there were still millions of passenger pigeons, but they were eventually hunted to extinction, as conservation measures were taken only after the species had passed the point of no return. Martha, the last, died in 1914 at the Cincinnati Zoo.

* “Lonesome George”, found in 1971, was Ecuador’s last Pinta Island tortoise. From the 17th century, around 200,000 individuals were hunted for their meat. Later, they struggled to compete for food after goats were brought to the island in the 1950s. Scientists tried to save the species through captive breeding before George died in 2012.

* “Ben” or “Benjamin” was the world’s last known thylacine, a marsupial carnivore also known as the Tasmanian tiger. The animal was given protected status only two months before Benjamin died in 1936 at the Beaumaris Zoo in Tasmania.

ON THE FIRE

There are a few species that may soon be reduced to their own endings. The world’s smallest porpoise – Mexico’s critically endangered vaquita – is down to just 18 individuals in the wild as populations have been decimated by fishing nets.

The Northern white rhino subspecies, the second largest land mammal after elephants, has no hope of recovery after the last male died in 2018. Only a female and her daughter are left.

These stories of endings matter, scientists say, precisely because so many extinctions happen out of sight.

“Somewhere at the core of our humanity, we recognize these creatures, we are touched by their story, and we feel compassion – and perhaps a moral compulsion – to help,” said Paula Ehrlich, President and CEO of the EO Wilson Biodiversity Foundation.

The Northern White Rhino is not just part of the world, she said. It is a world of its own – its own ecosystem – mowing fields by grazing, fertilizing fields where it walks, letting insects land on its skin, and then with birds that feed on those insects.

“Understanding all that an animal is and does to the world helps us understand that we are also part of nature—and we need nature to survive,” Ehrlich said.

EXTRACT WITH TIME

Unlike with the last ones, most species simply disappear into the wild without people noticing.

Scientists estimate that 881 animal species have become extinct since around 1500, dating back to the first records kept by the International Union for Conservation of Nature (IUCN) – the global scientific authority on the status of nature and wildlife. However, this is an extremely conservative estimate for species extinction over the past five centuries, as it represents only those cases that have been resolved with a high degree of certainty.

If we include animal species that scientists suspect may be extinct, that number jumps to 1,473. The bar is high to declare a species extinct—a sobering task that scientists are already reluctant to undertake.

“It’s hard to prove the negative, to prove you can’t find it,” said Sean O’Brien, an ecologist who heads the nonprofit NatureServe working to capture definitive data on North American species. set. “And it’s emotional. A botanist doesn’t want to declare it extinct because it feels like a failure.”

Among land vertebrates, or land animals with a backbone, 322 species have been declared extinct since 1500. Add the number of potentially extinct species and the number comes to 573.

For moisture-loving amphibians, vulnerable to both pollution and drought, things look particularly bleak with the extinction rate escalating over the last few decades. Only 37 species have gone extinct with a high degree of certainty since 1500. But scientists suspect more than 100 others have disappeared over the past 30-40 years, according to a 2015 study in the journal Science Advances.

Last recorded sightings increase over time, especially from the mid-19th century beginning of the Industrial Revolution. This shows that animals have increasingly fared, but also that our knowledge of nature has improved as we study and investigate more species.

There are many notable species among those that have disappeared since 1500. The dodo was last seen in 1662, within 65 years of its first being recorded. The Pinta Island tortoise was last seen in the wild in 1972.

Some disappearances have inspired public outcry, such as the 2016 extinction declaration for the tiny Christmas Island pipistrelle bat species, which was last seen in 2009. It was Australia’s first recorded mammal extinction in 50 years.

The loss of hundreds of species over 500 or so years may not seem significant when there are millions more living on the planet. But the speed at which species are now disappearing is unprecedented in the last 10 million years.

“We are now losing species faster than they can evolve,” O’Brien said.

MASS EXTRACTIONS

Many animals have become extinct naturally or due to causes unrelated to human activity. In a healthy environment, as species die off naturally, new species develop – and an evolutionary balance is maintained.

This turnover is based on what scientists consider a normal or background extinction rate.

But when the extinction rate jumps so high that more than 75% of the world’s species become extinct within the relatively short time span of less than 2 million years, it is considered a mass extinction event.

This has happened five times over the last half billion years, which we know from studying the Earth’s fossil record – with layers upon layers of sediment that buried the remains of animals over time. When a layer with a large and diverse number of animals is found, scientists can tell that a mass die-off has occurred.

Scientists warn we have entered a sixth mass extinction.

Under a normal extinction rate scenario, it would have taken at least 800 years and up to 10,000 years for the high number of vertebrate extinctions we saw in the last century, according to the 2015 paper in Science Advances.

“Despite our best efforts, the extinction rate is still estimated to be 1,000 times higher than before humans came on the scene,” Ehrlich said. “At this rate, half will be gone by the end of the century.”

UNKNOWN AND STILL THREATENED

As bad as it seems, scientists say the reality is probably even worse. Just looking at species extinctions doesn’t give the full picture, in part because scientists are so conservative about saying a species is gone. For example, even though Toughie was the last known individual of his kind, the IUCN still lists his species as “critically endangered, possibly extinct.”

More importantly, there is a vast reservoir of species that we have yet to discover. Scientists have identified about 1.2 million species in the world, but estimate there are about 8.7 million. That leaves about 7.5 million species that we think are out there but know nothing about—including whether or not they’re in trouble.

“Knowing what we’re doing about the impacts of climate change and habitat loss, it’s hard to imagine that thousands if not millions of species aren’t going extinct right now,” O’Brien said.

CONSERVATION OFFERS HOPE AS POPULATIONS DECLINE

The IUCN uses a series of categories to describe the condition of a species, as a way of identifying who is in trouble and when to help. But a species being listed as “least concern” or “near threatened” does not mean its populations are stable.

African lions, for example, have been listed as “vulnerable” for decades, but their numbers declined by 43% in 1993-2014, when the last population data was available. Dugongs, the chubby marine mammals also known as manatees, are listed as “vulnerable” worldwide, even as their declining populations in East Africa and New Caledonia were upgraded to “threatened” in December.

The decline of one or more populations of a species may indicate the beginning of a trend towards extinction.

As sobering as the situation may seem on a global scale, there are reasons for hope. The newly adopted Kunming-Montreal Global Biodiversity Framework in December will guide global conservation efforts through the decade to 2030. Among other things, the agreement intends to place 30% of the planet’s land and sea areas under protection by the end of the decade.

“It’s so overwhelming to think there are these species right on the edge,” O’Brien said. “But then the conservationists I work with remind me how many people care.”

Between 1993 and 2020, conservation measures such as habitat restoration or captive breeding helped prevent the extinction of up to 32 species of birds and as many as 16 mammals worldwide, according to conservative estimates in a 2020 study published in the journal Conservation Letters.

“Science democratizes the information for each country to know what it needs to do where,” says Ehrlich of the Wilson Foundation, which works to identify the best places in the world to protect biodiversity and prioritize nature. Before he died last year, Edward O. Wilson advocated putting half the planet under conservation and estimated that it would save 85% of the world’s species.

“We must humbly do the best we can to protect them now,” Ehrlich said. “We understand more about the intricate web of life that sustains nature—and us, as part of nature.”