Mass Extinction Threat: Earth on Verge of Huge Reset Button?
2010 09 03

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




Related Articles
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

NATO Exercise in Ukraine Coincided with MH-17 Shoot-down
2014 07 24
Rapid Trident was omitted from the flurry of coverage on the shoot-down MH-17. From the U.S. Army in Europe website: Rapid Trident supports interoperability among Ukraine, the United States, NATO and Partnership for Peace member nations. The exercise helps prepare participants to operate successfully in a joint, multinational, integrated environment with host-nation support from civil and governmental agencies. ...
Warning of ’imminent’ terror attack in Norway
2014 07 24
Norwegians were warned Thursday of the concrete possibility of a terror attack occurring in that country at the hands of people with connections to an extremist group in Syria. A press conference was called in Oslo, Norway on Thursday where an announcement was made of a "possible concrete threat" to national security in that country from terrorists related to an extremist ...
Judge says government can access everything in a Gmail account
2014 07 24
All your emails are belong to us. At least that’s what the latest court order from a judge in New York says. The warrant, granted on June 11, states that the government can access all the content and files contained in a Gmail account. Yes, this is a significant blow to privacy. The subject of this specific search relates to a money laundering ...
Scotland Yard Spied on Grieving Families: secret surveillance after police victim shot seven times in head ’by mistake’
2014 07 24
More terror from the ’anti-terror’ brigade. Undercover police gathered evidence on 18 grieving families By Rob Evans and Vikram Dodd | The Guardian Undercover police officers secretly gathered intelligence over two decades on 18 families fighting to get justice from the police, it was revealed on Thursday. The intelligence covering high-profile campaigns was collected between the mid-1980s and 2005, and affected grieving families ...
Air Algerie AH5017 with 116 onboard goes missing for hours, found crashed in Mali
2014 07 24
An Air Algerie flight carrying 110 passengers and six crew members has reportedly crashed in Mali after having disappeared from radar early on Thursday morning between Burkina Faso and Algeria. A French Ministry of Defense official told Fox News that the two French fighter jets located the wreckage of the plane, which had crashed in Mali. An airport official additionally confirmed ...
More News »