Mass Extinction Threat: Earth on Verge of Huge Reset Button?
By Jeremy Hsu | LiveScience.com
Mass extinctions have served as huge reset buttons that dramatically changed the diversity of species found in oceans all over the world, according to a comprehensive study of fossil records. The findings suggest humans will live in a very different future if they drive animals to extinction, because the loss of each species can alter entire ecosystems.
Some scientists have speculated that effects of humans — from hunting to climate change — are fueling another great mass extinction. A few go so far as to say we are entering a new geologic epoch, leaving the 10,000-year-old Holocene Epoch behind and entering the Anthropocene Epoch, marked by major changes to global temperatures and ocean chemistry, increased sediment erosion, and changes in biology that range from altered flowering times to shifts in migration patterns of birds and mammals and potential die-offs of tiny organisms that support the entire marine food chain.
The dodo, a flightless bird native to the Mascarene Islands in the Central Indian Ocean, became extinct around 1800. Pigs and monkeys, which destroyed dodo eggs, probably bore the greatest responsibility for the dodo’s extinction. Humans contributed to the problem by slaughtering thousands of dodos for meat.
Dodos became extinct on the island of Mauritius soon after 1680 and on the island of Reunion around 1750. They remained on the island of Rodriguez until 1800. Source
Scientists had once thought species diversity could help buffer a group of animals from such die-offs, either keeping them from heading toward extinction or helping them to bounce back. But having many diverse species also proved no guarantee of future success for any one group of animals, given that mass extinctions more or less wiped the slate clean, according to studies such as the latest one.
Then and now
Looking back in time, the diversity of large taxonomic groups (which include lots of species), such as snails or corals, mostly hovered around a certain equilibrium point that represented a diversity limit of species’ numbers. But that diversity limit also appears to have changed spontaneously throughout Earth’s history about every 200 million years.
How today’s extinction crisis — species today go extinct at a rate that may range from 10 to 100 times the so-called background extinction rate — may change the face of the planet and its species goes beyond what humans can predict, the researchers say.
"The main implication is that we’re really rolling the dice," said John Alroy, a paleobiologist at Macquarie University in Sydney, Australia. "We don’t know which groups will suffer the most, which groups will rebound the most quickly, or which ones will end up with higher or lower long-term equilibrium diversity levels."
What seems certain is that the fate of each animal group will differ greatly, Alroy said.
His analysis, detailed in the Sept. 3 issue of the journal Science, is based on almost 100,000 fossil collections in the Paleobiology Database (PaleoDB).
The findings revealed various examples of diversity shifts, including one that took place in a group of ocean bottom-dwelling bivalves called brachiopods, which are similar to clams and oysters. They dominated the Paleozoic era from 540 million to 250 million years ago, and branched out into new species during two huge adaptive spurts of growth in diversity – each time followed by a big crash.
The brachiopods then reached a low, but steady, equilibrium over the past 250 million years in which there wasn’t a surge or a crash in species’ numbers, and still live on today as a rare group of marine animals.
Counting creatures better
In the past, researchers have typically counted species in the fossil record by randomly drawing a set number of samples from each time period – a method that can leave out less common species. In fact two studies using the PaleoDB used this approach.
Instead, Alroy used a new approach called shareholder sampling, in which he tracked how frequently certain groups appeared in the fossil record, and then counted enough samples until he hit a target number representative of the proportion for each group.
"In some sense the older methods are a little like the American voting system – the first-past-the-post-winner method basically makes minority views invisible," said Charles Marshall, a paleontologist at the University of California, Berkeley, who did not take part in the study. "However, with proportional systems, minority views still get seats in parliament."
Marshall added that the study was the "most thorough quantitative analysis to date using global marine data." But he added that researchers will probably debate whether the PaleoDB data represents a complete-enough picture of the fossil record.
Nothing lasts forever
The idea that rules of diversity change should not come as a surprise for most researchers, according to Marshall.
"To me, the really interesting possibility is that some groups might not yet be close enough to their caps to have those caps be manifest yet," Marshall told LiveScience. Or "evolutionary innovation" might happen so quickly that new groups emerged to increase overall diversity, even if each sub-group reached a cap on diversity.
If anything, the record of past extinctions has shown the difficulty of predicting which groups win out in the long run. "Surviving is one thing and recovering is another," said Marshall, who wrote a Perspectives piece about the study in the same issue of Science.
One of the few consistent patterns is that growth spurts in diversity can apparently happen at any time, according to Alroy. He added that the background extinction of individual species has also remained consistent – the average species lasts just a few million years
Of course, the ongoing extinction crisis of modern times goes far beyond the background extinction rate. Alroy noted that it could not only wipe out entire branches of evolutionary history, but may also change the ecosystems shaped by each species.
That means today’s species matter for environments around the world, and so humans can’t simply expect replacements from the diverse species of the future.
"If we lose all the reef builders, we may not get back the physical reefs for millions of years no matter how fast we get back all the species diversity in a simple sense," Alroy said.
Article from: livescience.com
What Causes Mass Extinctions?
Mankind must abandon earth or face extinction: Hawking
’Extinct’ Whale Surfaces Again
The Tasmanian Tiger: Is the strange creature extinct or hiding from humans?
Human Extinction the Genetic Genocide a Call for the Survival of the Pure-Human Race
Bringing Back The Extinct Aurochs
Scientists hope to clone extinct species
Woolly-mammoth gene study changes extinction theory
Did Comets Cause Ancient American Extinctions?
Humans flirted with extinction 70,000 years ago
Medical plants ’face extinction’
Latest News from our Front Page
The Pilgrims Were Definitely Not Like Modern-Day Refugees
This upcoming Thanksgiving Day is sure to offer you and your family plenty of opportunities to argue over whether America should be welcoming Syrian refugees.
If you have any liberal relatives or friends coming over for your Thursday feast, theyâ€™re going to relish the chance to tell everyone that the Pilgrims were refugees too â€” and hope that statement decimates all ...
ISIS to France: "We will be coming. Victory has been promised to us by Allah"
Homegrown French ISIS fighters have issued a chilling threat of new attacks on France just 24 hours after the terrorist group used movie footage of the Eiffel Tower's collapse in another video.
A balaclava-clad militant is seen warning 'we will be coming, we will come to crush your country' in footage posted on Twitter earlier today.
It is unclear where the film ...
ISIS teenage 'poster girl' Samra Kesinovic 'beaten to death' as she tried to flee the group
She appeared in social media images for the group carrying a Kalashnikov and surrounded by armed men
A teenage girl who ran away from her Vienna home to join Isis in Syria has reportedly been beaten to death by the group after trying to escape.
Samra Kesinovic, 17, travelled to Syria last year with her friend Sabina Selimovic, 15.
The two became a ...
The Right Stuff's flagship podcast "The Daily Shoah" has been censored by Soundcloud
Editor's note: The PC corporate moral police strike again. Just as Radio 3Fourteen & Red Ice Radio were censored from iTunes, The Daily Shoah was pulled from Soundcloud today. As per usual, there is a double standard, they allow any kind of anti-White material:
No counter culture humor making fun of the genocidal mainstream garbage is allowed!
Soundcloud took it upon ...
Merkel Welcomes A Million More: Vows To Stand By Refugee Policy Despite Security Fears
Chancellor Angela Merkel vowed on Wednesday to stick to her open-door refugee policy, defying criticism at home and abroad which has intensified due to growing fears about a potential security risk after the Islamist attacks in Paris.
Conservative Merkel faces splits in her right-left coalition and pressure from EU states, including France, over her insistence that Germany can cope with up ...
|More News » |