The creatures that went extinct or likely went extinct in 2019 are as follows:

1. The Hawaiian snail Achatinella apexfulva: The last known member of its species, "George" died in a tank in a Hawaiian lab on New Year's Day. The species is likely extinct, said David Sischo, the snail extinction prevention program coordinator at the Hawaii Department of Land and Natural Resources.

"I’ve been scouring the mountains trying to find more," said Sischo. "People have been looking for them for well over 20 years."

Like many native Hawaiian snails, Achatinella apexfulva died out because decades ago the Hawaii State Department of Agriculture intentionally introduced an invasive species (rosy wolfsnail) to exterminate another introduced invasive species. The plan had an unintended fallout: The out-of-control wolfsnails ate up Achatinella apexfulva.

"George." Image: HAWAII DEPARTMENT OF LAND AND NATURAL RESOURCES

2. Australia's Bramble Cay melomys, Melomys rubicola: Inhabiting a small 12-acre island north of the Australian continent, Australia's Bramble Cay melomys was a critically endangered rodent. The Australian government subtly declared the rats' extinction in February.

Rising seas — largely a consequence of rapidly melting glaciers and ice sheets — destroyed the rodent's finite, low-lying habitat.

Gone for good: a Bramble Cay melomys Image: State of Queensland

3. Sumatran Rhino, Dicerorhinus sumatrensis (regional extinction): Malaysia's last Sumatran rhino died of cancer in November.

"It's a huge shame," said Barney Long, Global Wildlife Conservation's senior director of species conservation.

Succumbing to habitat loss and poaching, fewer than 80 Sumatran rhinos now exist in the wild, scattered around Indonesia.

4. Bahama nuthatch, Sitta pusilla insularis (potentially extinct): Before Hurricane Dorian walloped the Bahamas in September, biologists estimated that just two Bahama nuthatches remained.

Then, a Category 5 hurricane hit, thrashing the animals' native home.

"When humans endanger populations, they become more susceptible to chance events," said Seabird McKeon, an ecologist at the University of Central Florida, noting the birds' potential extinction.

A Bahama nuthatch, before Dorian struck. Image: University of east anglia

Why aren't there any plants on this list?

As any biologist will tell you, it's profoundly difficult to know with certainty that any species is truly gone for good (unless they only live, or lived, on a well-scoured island).

But with plants, it's all the more challenging, explained Eimear Nic Lughadha, who leads the Conservation Assessment and Analysis team at the Royal Botanical Gardens, Kew.

First, there's the trouble of actually locating specific plant species in diverse, plant-crowded terrain. What's more, some seeds can persist in the soil for years and then sprout up. "The plants can reappear," said Nic Lughadha.

Of 1,234 plants declared extinct since Carl Linnaeus’ legendary plant species compendium, Species Plantarum, was published in 1753, about half the species were rediscovered.

"That makes us cautious," Nic Lughadha emphasized.

Still, some 571 plants have gone extinct since Linnaeus’ time. But no plant extinctions have been confirmed this year. "Nothing we assessed this year has been declared extinct," Nic Lughadha said.

What do all the extinct species this year have in common?

All these species are islanders. That makes them all the more vulnerable.

Island species have smaller habitats and relatively small populations, so they're inherently susceptible to one big storm, development, or other catastrophe, said McKeon.

The Bramble Cay melomys, for example, had its tiny home devastated, and had nowhere to flee.

But, critically, habitat destruction (often for timber or agriculture) is also making "figurative islands" around species, noted McKeon.

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This is particularly problematic because burgeoning genetic research has found that species once thought to encompass entire regions (like across the sprawling Amazon basin), are actually multiple, though similar, species.

"This means that the starting amount of habitat and population size is initially lower, and risk of being trapped on an 'island' — literal or figurative — is greater than we previously thought," said McKeon.

What endangered species are flying under the radar?

Most of them.

People love big charismatic animals. And they should. But, generally, "these small, unknown species are the ones disappearing," said Global Wildlife Conservation's Long.

Who had heard of the Hawaiian Snail Achatinella apexfulva before 2019? Here's a terrible stat: A total of 752 land snail species have been identified in Hawaii, covering a range of 10 families. But in each family, between 60 to 90 percent of the species are now extinct, said Hawaii's Sischo.

"Most of us are familiar with the Orangutan, but relatively few of us are aware of the critically endangered birds of Southeast Asia, such as Sulu Hornbill, Siau Scops-owl Otus siaoensis, Annobon Scops-owl Otus feae, Cebu Flowerpecker Dicaeum quadricolor, or Cerulean Paradise-flycatcher Eutrichomyias rowleyi, any of which could have been lost to palm oil [habitat destruction] this year," said McKeon.

"There are instances of a species seen once, and never seen again."

Some species are likely lost before scientists even have an opportunity to properly document or understand them, said Nico Arcilla, a bird biologist with the International Bird Conservation Partnership.

"There are instances of a species seen once, and never seen again," she said, noting species in centuries-old Brazillian natural history books (some of which were "big and tasty") that haven't been seen in decades, or ever.

What can we do?

A lot.

"We can’t solve every problem, but we can solve most of them," said Arcilla.

Hell, there's even a lot you can do this month. Here's a simple, immensely important one: If you own a cat, keep it inside. Domestic cats, which are excellent hunters, slaughter birds.

"We could save a huge number of birds," said Arcilla, noting that cats are either the number one or number two killer of birds in North America. "Just one person keeping their cat indoors can save hundreds, maybe thousands, of birds," she said. "That’s a no-brainer."

Have a yard? Buck the ecological disaster that are lawns. Lawns don't support diverse life. Instead, try native plants that invite life. "Habitat is crucial," said Arcilla.

Dragging back a species from near extinction is a daunting circumstance, but devoted conservation endeavors work: Look at the whooping crane, California condor, bald eagle, and elephant seal.

"The clock is ticking"

And perhaps, the same will happen for the Sumatran rhino. There are, as noted above, some 80 individuals left.

"The clock is ticking," said Long.

Conservationists have "literally five years" to save the Sumatran rhinos, Long stressed. Why? The 80 or so rhinos are geographically separated and aging. Critically, this separation means they're not breeding. "They'll soon lose their chance to reproduce [in about five years]," said Long. The large mammals must be located, moved around, and encouraged to mate.

The current situation is grim. Think of it as 80 humans locked inside 11 different rooms, explained Long. They can't meet each other. "If we have the same conversation in five years and have not got the breeding going, I'd say the species is close to functionally extinct," he said.

That means the species can no longer perpetuate itself. There will be rhinos left, but we will just watch them get old and die. Just like George, the snail.

"We know that for endangered species with low populations, each year is a roll of the dice," said McKeon. "Double sixes might be a population gain, and snake eyes could be a final extinction."