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Earth May Be in Early Days of 6th Mass Extinction

Earth may be in the early stages of a sixth mass extinction, an international team of scientists says.

Image: Neil deGrasse Tyson walks over to ‘The Halls of Extinction’ - Cosmos: A Space time Odyssey

Animals and plants are threatened. More than 320 land vertebrates have gone extinct since 1500, the researchers said. The world’s remaining animals with backbones are 25 percent less abundant than in 1500— a trend also seen in invertebrate animals, such as crustaceans, worms and butterflies, the scientists reported.

The previous mass extinction, which wiped out the dinosaurs, happened about 65 million years ago, likely from a catastrophic asteroid that collided with Earth. In contrast, the looming sixth mass extinction is linked to human activity, Rodolfo Dirzo, a professor of biology at Stanford University in California, said in a statement. Dirzo is the lead author of the new review of past research on the topic, which suggests Earth is in the early days of this sixth mass extinction.

A past study, which involved data from the fossil record and modern-day conservation biology, suggested Earth could enter such a mass extinction within the next 300 to 2,000 years. That study was detailed in the March 2, 2011, issue of the journal Nature.

Up to one-third of all vertebrates are threatened or endangered, the researchers said. Large animals — such as elephants, rhinoceroses and polar bears — have the highest rates of decline, which is a trend shared by other mass extinctions. These large animals are at particular risk because they tend to have few offspring and low population growth rates. Hunters and poachers, however, find their fur, meat, tusks or horns attractive targets.

Losing a species of large animal can have unexpected effects on the ecosystem and nearby human developments, a process known as defaunation. In one study, researchers isolated patches of land from animals, including zebra, giraffes and elephants. Without the animals, the grass and shrubs grew tall, and the soil became looser. Rodents quickly took over and doubled in numbers, eating the seeds from the plants and living in the patchy soil that was relatively predator-free.

Rodents can carry diseases and parasites that infect people, the researchers said.

"Where human density is high, you get high rates of defaunation, high incidence of rodents and thus high levels of pathogens, which increases the risks of disease transmission," Dirzo said. "Who would have thought that just defaunation would have all these dramatic consequences? But it can be a vicious circle."

The decline of big animals affects not only vegetation, but also invertebrates. In the past 50 years, the human population has doubled, and the number of invertebrate animals has dropped by 45 percent, the researchers said. Much of the loss is a result of habitat destruction and global climate disruption, the researchers said.

kqedscience:

Woolly Mammoth Fossils Raise Red Flags on the Road to Extinction

A surprising discovery in woolly mammoth fossils recovered from the North Sea off the coast of the Netherlands suggests that inbreeding and harsh conditions plagued the ice age giants near the end of their reign on Earth.

Learn more from Liza Gross at KQED Science. 

mothernaturenetwork:

Debating the dodo: Extinction date challenged by journals
The flightless bird is thought to have gone extinct by 1662, but one geologist has discovered observations that may challenge that extinction date.

Lost World Locked in Stone at Fossil Lake

With just two inhabited buildings and a population of five, Fossil, Wyo., is all but a ghost town today. But as far as ghosts go, the ones at Fossil are pretty remarkable — 50-million-year-old monitor lizards, stingrays and freakishly long-tailed turtles among them.

Fossil showed promise of becoming a train-stop city during America’s westward expansion. The town’s real golden age, however, may have been the early Eocene, when it was covered in a subtropical lake with an incredible diversity of aquatic life, surrounded by lush mountains and active volcanoes.

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Image 1: This is the most complete skeleton of a so-called dawn horse ever discovered. This specimen of Protorohippus venticolus was much more diminutive than today’s horses, standing less than two feet high at the shoulder, but its long back legs suggest it was a good jumper. Perhaps it was less skilled as a swimmer; researchers aren’t sure how the horse ended up at the bottom of the middle of Fossil Lake but they suspect it drowned, possibly trying to escape a predator. Credit: Photo by Lance Grande from The Lost World of Fossil Lake: Snapshots from Deep Time, © 2013, published by the University of Chicago Press.

Image 2: This fossil immortalizes stingray sex of the Eocene. The male and female fat-tailed stingrays (Asterotrygon maloneyi) shown here were likely mating or just about to mate when they were killed, researchers believe. Credit: Photo by Lance Grande from The Lost World of Fossil Lake: Snapshots from Deep Time, © 2013, published by the University of Chicago Press.

electricspacekoolaid:

In Earth Undergoing a 6th Mass Extinction? - 99.9% of all Past Species Extinct

Of all species that have existed on Earth, 99.9 percent are now extinct. Many of them perished in five cataclysmic events. The classical “Big Five” mass extinctions identified by Raup and Sepkoski are widely agreed upon as some of the most significant: End Ordovician, Late Devonian, End Permian, End Triassic, and End Cretaceous. According to a recent poll, seven out of ten biologists think we are currently in the throes of a sixth mass extinction. Some say it could wipe out as many as 90 percent of all species living today. Other scientists dispute such dire projections.

“If you look at the fossil record, it is just littered with dead bodies from past catastrophes,” observes University of Washington paleontologist Peter Ward. Ward says that only one extinction in Earth’s past was caused by an asteroid impact – the event 65 million years ago that ended the age of the dinosaurs. All the rest, he claims, were caused by global warming.

Ward’s study, Under a Green Sky, explores extinctions in Earth’s past and predicts extinctions to come in the future. Ward demonstrates that the ancient past is not just of academic concern. Everyone has heard about how an asteroid did in the dinosaurs, and NASA and other agencies now track Near Earth objects.

Unfortunately, we may not be protecting ourselves against the likeliest cause of our species’ demise. Ward explains how those extinctions happened, and then applies those chilling lessons to the modern day: expect drought, superstorms, poison–belching oceans, mass extinction of much life, and sickly green skies.

The significant points Ward stresses are geologically rapid climate change has been the underlying cause of most great “extinction” events. Those events have been, observed Harvard evolutionary biologist Stephen Gould, major drivers of evolution.

Drastic climate change has not always been gradual; there is solid empirical evidence of catastrophic warming events taking place in centuries, perhaps even decades. The impact of atmospheric warming is most potent in its modification of ocean chemistry and of circulating currents; warming inevitably leads to non-mixing anoxic dead seas.

We are already in the middle, not the beginning, of an anthropogenic global warming, caused by agriculture and deforestation, which began some 10,000 years ago but which is now accelerating exponentially; though the earliest wave of anthropogenic warming has been stabilizing and beneficial to human development, it appears to have the potential for catastrophic effects within a lifetime or two.

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currrentbiology:

A catastrophic mass extinction of birds in the Pacific Islands followed the arrival of the first people

Research carried out by the Zoological Society of London (ZSL) and collaborators reveals that the last region on earth to be colonised by humans (tropical Pacific Islands) was home to more than 1,000 species of birds that went extinct soon after people reached their island homes.

The paper was published March 25,2013 in the journal Proceedings of the National Academy of Sciences USA.

jtotheizzoe:

The Sticky Stick Insects of Lord Howe Island

That’s Ball’s Pyramid, a dormant volcanic spire off the coast of Australia’s Lord Howe Island, and yes, it’s a real place. It’s a starkly beautiful place, and it’s home to this enormous insect, the “tree lobster” (aptly named, because holy crap):

image

Those insects live under a single bush on the edge of a single cliff on a lonely crescent of rock in the South Pacific. How in the world did that happen?

They used to live all over Lord Howe Island, the larger neighboring land mass, until a ship ran aground there in 1918. In the process, a handful of rats swam ashore and turned the island into a stick insect-eating buffet/mating playground. In short, the tree lobster was wiped out, extinct, kaput, finished. Or so they thought …

In 2001, a team of climbers ascended the face of Ball’s Pyramid, looked in the rocky soil beneath a lonely, windswept bush, and found a couple dozen tree lobsters, alive and well! How did they get there? The best guess is that they hitched an airborne ride on some nesting material brought to the cliff faces by birds that inhabit the Pyramid. A couple of them landed beneath that bush, and the rest is history. A lonely, 80 year history.

Later this month, Bespoke Animation will be releasing a short animated film about this bug-gone-missing story titled Sticky (and they could use some help crossing over the finish line on their funding, so if you’d like to help check here). Here’s the trailer, which looks simply wonderful:

Captive breeding of the insects has commenced, and once the rat problem on Lord Howe Island is under control scientists hope to reintroduce them to their native habitat. It’s an extinction story with a happy ending! For more on Ball’s Pyramid tree lobsters, check out this Robert Krulwich story, or this feature from Becky Crew. And you definitely want to see a video of one of these guys hatching from its egg … wow!

mothernaturenetwork:

Blue iguana crawls away from extinction
Found only on Cayman Islands, blue iguana species has been updated from critically endangered to only endangered.

wespeakfortheearth:

Rhino Poaching: An Extinction Crisis

The number of rhinos being poached and killed for their horns began to climb dramatically about five years ago after several quiet decades.

At the beginning of the 20th century only a handful of rhinos were being killed each year. In 2009 122 rhinos were killed for their horns in South Africa. A year later, that number had nearly tripled to 333. It climbed again in 2011, reaching 448 animals. This year has already broken that record: as of October 15, a record 455 rhinos have already been killed in South Africa.

Although this is a worldwide problem, the best counts of rhino poaching come out of South Africa, where more than 80 percent of the world’s rhinos now live, but other countries face similar threats. At least 15 rhinos have been killed in India so far this year. The last 35 or so Javan rhinos in Indonesia are under constant guard (but still threatened). The western black rhino was poached into extinction in Cameroon around the year 2000, and the final rhino in Vietnam (a subspecies of the Javan rhino) was killed by poachers in 2010.

Although the majority of poached rhinos are southern white rhinoceri—the most populous of the five rhino species—all species are affected. For some rhinos, any loss could affect the entire future of their species.

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herplove:

U.S. researchers have identified two dozen new species of lizards on the Caribbean islands, and about half of them may be extinct or close to extinction.

alchymista:

Rhino’s end

From now on, the only place you’ll see this subspecies of black rhino from western Africa is in photographs or stuffed in museums. That’s because this year, the western black rhino (Diceros bicornis longipipes) is officially extinct, and others are clinging on by a thread. In all, the International Union for Conservation of Nature says that a quarter of all mammals are at risk of extinction. It’s not all bad news though. One of conservation’s success stories is (Ceratotherium simum simum), a subspecies of the African southern white rhino, which has soared in number from less than 100 individuals to 20,000 since the end of the 19th century. 

discoverynews:

Big Question for 2012: What Animals Could Go Extinct?

The world’s biodiversity is declining at an unprecedented rate. As a result, more extinctions than usual are predicted for the coming year.

Jennifer Viegas has a breakdown here of what animals are in peril.

(That’s a picture above of the Golden Toad which was last seen on May 15, 1989, and is presumed to be extinct.)

mothernaturenetwork:

The last documented sighting of China’s baiji dolphin, or Yantze River dolphin, was in 2002, and while the species is listed as critically endangered, scientists say it may already be extinct. In 2006, scientists from the Baiji Foundation traveled up the Yangtze River for more than 2,000 miles equipped with optical instruments and underwater microphones, but were unable to detect any surviving dolphins. The foundation published a report on the expedition and declared the animal functionally extinct, meaning too few potential breeding pairs remained to ensure the species’ survival.
10 animals presumed extinct in the last decade

Origin of Dinosaur-Killing Asteroid Is Still a Mystery

The source of the asteroid that killed off the dinosaurs 65 million years ago remains a mystery, a new study finds.

Some researchers had thought the deadly asteroid was a piece of a larger space rock called Baptistina. Baptistina broke apart after a massive in-space collision about 160 million years ago, the theory went, spawning a swarm of mountain-size chunks of rock. One of those eventually slammed into Earth, killing off the dinosaurs and many other species.

Scientists are confident that a 6-mile-wide (10-kilometer asteroid) is indeed what wiped out the dinosaurs. But new observations from NASA’s Wide-field Infrared Survey Explorer (WISE) space telescope suggest the space rock didn’t come from Baptistina.

The timing just isn’t right, according to the new study.

"As a result of the WISE science team’s investigation, the demise of the dinosaurs remains in the cold case files," said Lindley Johnson, program executive for the Near Earth Object Observation Program at NASA headquarters in Washington, in a statement.

Questioning The Theory

Baptistina first came under suspicion in some astronomers’ minds after a 2007 study. In that work, researchers used visible-light data from ground-based telescopes to estimate the size and reflectivity of the Baptistina “family” — the pieces of the broken-apart space rock.

With these estimates in hand, researchers determined that the big space rock likely broke apart about 160 million years ago. That would have given plenty of time for the Baptistina family asteroids to disperse to different and potentially dangerous orbits by the time of the dino-killing impact.

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