Nature is in crisis, and it's only getting worse. As species vanish at a rate not seen in 10 million years, more than 1 million species are on the brink.
Scientists say that humans are driving this extinction crisis through activities that take over animal habitats, pollute nature, and fuel global warming. A new global deal to protect nature agreed on Dec. 19 has the potential to help, and scientists are urging the world’s nations to ensure the deal is a success.
When an animal species is lost, a whole set of characteristics disappears along with it - genes, behaviors, activities, and interactions with other plants and animals that may have taken thousands or millions - even billions - of years to evolve.
Whatever role that species plays within an ecosystem is lost, too, whether pollinating certain plants, churning nutrients in the soil, fertilizing forests, or keeping other animal populations in check, among other things. If that function is crucial to the health of an ecosystem, the animals' disappearance can cause a landscape to transform.
Lose too many species, and the results could be catastrophic, leading an entire system to collapse.
Gone forever
Hundreds of unique animals have vanished worldwide in the last five centuries, such as the flightless Dodo bird killed off from the island of Mauritius in the late 1600s.
In many cases, humans were to blame - first by fishing or hunting, as was the case with South Africa's zebra subspecies Quagga, hunted to its end in the late 19th century - and more recently through activities that polluted, disrupted, or took over wild habitats.
Before a species goes extinct, it may already be considered "functionally extinct" – with insufficient individuals to ensure it survives. More recent extinctions have allowed humans to interact with some species' last known individuals, "endlings." When they go, that's the end of those evolutionary lines – as occurred in these iconic cases:
"Toughie" was the last known individual of the Rabb's Fringe-Limbed tree frog. All but a few dozen of his species had been wiped out by chytrid fungus in the wild in Panama. In his enclosure at the Atlanta Botanical Garden, he was calling out vain for a mate that didn’t exist. He died in 2016.
The story of the 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 was past 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, humans hunted some 200,000 individuals for their meat. Later, they struggled to compete for food after humans brought goats 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 known as the Tasmanian tiger. The animal was given protective status only two months before Benjamin died in 1936 in the Beaumaris Zoo in Tasmania.
On the brink
Nature could soon reduce some species to their endings. The world's smallest porpoise - Mexico's critically endangered vaquita - is down to just 18 individuals in the wild as fishing nets have ravaged populations.
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 endlings matter, scientists say, precisely because so many extinctions happen out of sight.
"Somewhere in the core of our humanity, we recognize these creatures, their story touches us, and we feel compassion - and maybe also a moral compulsion - to help," said Paula Ehrlich, president and CEO of the EO Wilson Biodiversity Foundation.
She said the Northern white rhino isn't just a part of the world. It's a world unto itself - its ecosystem - mowing fields through grazing, fertilizing lands where it walks, having insects land on its skin, and then with birds feeding off those insects.
"Understanding everything an animal is and does for the world helps us understand that we, too, are a part of nature - and we need nature to survive," Ehrlich said.
Extinction over time
Unlike the endings, most species fade away in the wild without people noticing.
Scientists count 881 animal species as having gone extinct since around 1500, dating to the first records held by the International Union for Conservation of Nature (IUCN) – the global scientific authority on the status of nature and wildlife. That's an extremely conservative estimate for species extinction over the last five centuries, though, as it represents only the cases resolved with a high degree of certainty.
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