Ocean acidification triggered mass extinctions 252 million years ago
Last updated on 18 April 2015, 9:17 am
Biggest extinction known on Earth result of oceans turned acid by CO2, the main gas driving human-caused climate change
By Tim Radford
Scientists have identified the lethal agency that caused the single most catastrophic event in the history of life on Earth.
The mass extinction at the boundary of the Permian and Triassic eras 252 million years ago was caused by the acidification of the world’s oceans, as a consequence of an increase in atmospheric carbon dioxide.
The Permian Extinction – sometimes called “the Great Dying” – seemed to all but obliterate life in the oceans, and perhaps on land. More than 90% of all species disappeared, more than 80% of all genera, and more than 50% of all marine families were extinguished in one prolonged calamity.
All life on Earth today has descended from the few survivors of this far-off episode. Palaeontologists, geologists, climate scientists and astronomers have all speculated on the probable cause.
The latest and most confident analysis is based on a new study of ancient marine sediments and delivers obvious parallels with processes that are – for different reasons − occurring again today.
Report: Global coral reef survey highlights climate threat
Matthew Clarkson of the University of Edinburgh in Scotland (but now at the University of Otago in New Zealand) and colleagues report in the journal Science that they examined limestone from the United Arab Emirates and found, in the isotope ratios of the element boron, evidence of ocean acidity in carbonate rocks that were laid down as sediment at the bottom of the ocean 250 million years ago.
A change in the isotope ratios, they calculated, would have indicated a significant shift in seawater chemistry.
Over the last 40 years, researchers have introduced a whole suite of plausible triggers for the Permian extinction, but at last one team had clear evidence of increased atmospheric carbon, probably from a prolonged and convulsive series of volcanic eruptions that gave rise to vast, ancient geological formations now known as the Siberian Traps.
“Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now”, said Dr Clarkson.
“This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions.”
Report: Ocean acidification causes US$1 trillion of damage a year
There has been recent evidence that this present change in the pH of ocean waters (pH is a measure of its acidity) as a consequence of fossil fuel combustion in the last two centuries has already disturbed the behaviour of some fish species, threatened to affect oyster fisheries and coral reefs, and even to alter whole ocean ecosystems.
The changes in the Permian were not sudden: ecosystems already seriously under stress because of lack of oxygen or rising temperatures were then dramatically affected by discharges of carbon dioxide that were probably much greater than all the modern world’s existing fossil fuel reserves could deliver.
As the oceans became more acidic, many species were extinguished forever: among them the trilobites.
The whole chain of events took 60,000 years. Humans have been burning fossil fuels for only 200 years, but, the researchers point out, in the Permian crisis, carbon was probably being released into the atmosphere at the rate of about 2.4 billion tons a year.
Right now, humans are estimated to be releasing carbon from fossil fuels at the rate of 10 billion tons a year.
This article was produced by the Climate News Network
Close to half of all living species on the Earth could disappear by the end of this century, and humans will be the cause.
This is the Sixth Mass Extinction — a loss of life that could rival the die-out that caused the dinosaurs to disappear 65 millions years ago after an asteroid hit the planet.
This time, though, we’re the asteroid.
At least that's how Elizabeth Kolbert, the author of "The Sixth Extinction," sees it.
"We are deciding," Kolbert writes, "without quite meaning to, which evolutionary pathways will remain open and which will forever be closed. No other creature has ever managed this, and it will, unfortunately, be our most enduring legacy."
In "The Sixth Extinction," Kolbert traces our understanding of extinction from the first time it was proposed as a theory in the 1740s until now, with scientists mostly agreeing that humans may be causing it.
It took scientists a long time to accept that entire species could disappear
It used to be that when researchers came across old animal bones, their first goal was to identify them with a species that already existed. In 1739, for example, when a group of researchers unearthed the first Mastodon bones, they assumed they were looking at the remains of two different animals — an elephant and a hippopotamus.
It wasn't until French naturalist Georges Cuvier suggested that the bones were from "a world previous to ours" that researchers first started to consider the idea that an entire species could have existed and then disappeared.
This realization should awaken us to the idea that our impact on the planet could have serious implications.
One of the main culprits in the sixth extinction, Kolbert says, is climate change, but modern agriculture and a rapidly growing human population have contributed as well. By warming the planet, introducing invasive species to different areas, and encouraging the spread of previously contained fungi and viruses, people are killing the life around us.
"No creature has ever altered life on the planet in this way before, and yet other, comparable events have occurred. Very, very occasionally in the distant past, the planet has undergone change so wrenching that the diversity of life has plummeted. Five of these ancient events were catastrophic enough that they're put in their own category: the so-called Big Five. In what seems like a fantastic coincidence, but is probably no coincidence at all, the history of these events is recovered just as people come to realize that they are causing another one."
We know what mass extinctions look like. And a growing number of scientists have agreed that we are likely causing a new one.
Yet we are doing surprisingly little to curb the tide.
"It is estimated," Kolbert writes, "that one-third of all reef-building corals, a third of all fresh-water mollusks, a third of sharks and rays, a quarter of all mammals, a fifth of all reptiles, and a sixth of all birds are headed towards oblivion."
That adds up to between 30% and 50% of all life on Earth that could be gone by the end of the century — unless we start taking action now.
-------------------- Wise men learn more from fools than fools from the wise. Posts: 3777 | From: beautiful California | Registered: Sep 2008
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cash, WE caused isis, just like we caused the Taliban.
when Sadam invaded kuwiat, House Saud asked us to defend them- the younger sons of house Saud were insulted by their Elders. They wanted to defend the Realm instead of US. They are the ones who funded 9-11. It is known. Isis in one form or another was not only predicted right here by me, it was predicted by Elder Bush when he left sadam in power after the 1st gulf war. The power vacuum was too great. The culture there demands dictatorial presence and has for thousands of years.
Don't you find it somewhat incredible that the two longest wars we've been in (the Nam and Afgnaistan) are both high poppy production regions and after both wars got rollimg, we are flooded with heroin?
The differnce this time is that we allowed mercenary contractors to operate openly. The CIA doesn't need the cash anymore, hell they have google now. So who is operatin the drug flow systems? Look int he US Senate that's where the favors are traded. This meth and date rape drug bust in Cochranas office was caught by a postal inspector? Sheesh that's bone cancer man...
As to CO2 in the oceans? We are coming to a sort of judgement day, the die is set. Enjoy htis phase of civilisation while it's here, it can't last like this. It is known.
-------------------- Don't envy the happiness of those who live in a fool's paradise. Posts: 36378 | From: USA | Registered: Sep 2003
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