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Earth hit by mass extinctions 'every 27m years' – Telegraph

By Tom Chivers

Original Telegraph article Published: 3:30PM BST 12 Jul 2010


Postosuchus (left) and Desmatosuchus, two early reptile species that went extinct before the dinosaurs’ rule. Mass extinctions hit Earth every 27 million years, say palaeontologists.

Postosuchus (left) and Desmatosuchus, two early reptile species that went extinct before the dinosaurs’ rule. Mass extinctions hit Earth every 27 million years, say palaeontologists. Photo: REUTERS

Graph showing extinction events from the last 500 million years.

Graph showing extinction events from the last 500 million years.

An artist’s impression of an asteroid striking the Earth. Earth hit by catastrophe ‘every 27m years’

An artist’s impression of an asteroid striking the Earth. The study suggests that a celestial body is not responsible for the extinctions. Photo: REUTERS

For at least the last 500 million years, say Adrian Melott, an astrophysicist at the University of Kansas, and Richard Bambach, a palaeontologist at the Smithsonian Institute, there has been a burst of extinctions every 27 million years.

Periodic mass extinctions have been posited before, and it has been suggested that it means the Sun has a huge, dark neighbour which orbits it every 27 million years, each time knocking a shower of comets out of the Oort Cloud at the fringes of the solar system and sending them crashing into Earth. This hypothetical dark satellite was called “Nemesis”.

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But the regularity of the extinctions and the timescale they occur over – the 500 million years examined by Dr Melott and Dr Bambach is almost double that earlier studies have looked at – seem to rule that out.

This is because in the last 500 million years the Sun has had close encounters with many other, known stars. The gravitational pull of these stars would have affected the orbit of Nemesis, causing it to lose the regular 27 million year cycle. The peak should either have been slowly changed by up to 20 per cent, causing it to smear out over the aeons, or to suddenly change, giving two or more peaks on a single cycle. Instead, it is based around a regular 27 million year cycle, with a 99 per cent chance that it’s not random chance. The researchers say: “Fossil data, which motivated the idea of Nemesis, now militate against it.”

This implies that it is not a hidden celestial body, but something closer to home, since it is unlikely that anything in space would maintain such a regular heartbeat over so long a time.

The extinctions range from utter catastrophe, devastating the majority of species on Earth, to smaller ones like the most recent, which destroyed 10 per cent of known species. And while they happen once every 27 million years, they do not arrive on cue, but up to 10 million years either side of the due date.

However, there is no immediate panic. The last such event took place 10 million years ago, so there should be plenty of time to work out what is going on before the next one comes.

The paper is published in the journal Solar and Stellar Astrophysics. Story via The Register and Technology Review.

via Earth hit by mass extinctions ‘every 27m years’ – Telegraph.

Bat Caves Closed by Feds – ScienceInsider

More on the ‘White Nose Syndrome’ that is wiping out North American bat species….

Bat Caves Closed by Feds – ScienceInsider

To stop the possible western spread of white-nose syndrome, the U.S. Forest Service has issued an order to temporarily shut all caves and abandoned mines on federal lands in Colorado, Wyoming, South Dakota, Nebraska, and Kansas.

In a press release, Bat Conservation International, whose staff includes a number of respected scientists, says it supports the measure:

White-nose Syndrome is the most severe threat ever faced by North American bats. More than 1 million bats have been killed by WNS since it was found in a single New York cave in 2006. Mortality rates at some hibernation sites have reached almost 100 percent, and species extinctions are increasingly likely. Top scientists are searching desperately for solutions, but they have found no means of curing or preventing this disease or even of slowing its disastrous spread.

The one-year closure of western caves is an effort to buy time to examine all options. In this crisis, the decision is reasonable and prudent. Simply waiting for WNS to arrive before taking decisive action is far too risky.

via Bat Caves Closed by Feds – ScienceInsider.

Critical Ocean Organisms Are Disappearing – ScienceNOW

This is totally messed up! We are sooooo screwed!

Original Article form ScienceNOW

The number of marine phytoplankton, the microscopic organisms that gobble greenhouse gases and directly or indirectly feed every animal in the ocean, has been declining by about 1% per year, according to a new study. If the trend continues, it could decimate ocean food chains and accelerate global warming.

Researchers know that phytoplankton numbers have been dropping for the past 30 years. Satellite images show a decline in the concentration of chlorophyll—a green pigment that helps phytoplankton photosynthesize. But because satellites have been collecting data only since the late 1970s, scientists couldn’t determine whether this drop was a long-term trend or just a fluke.

To get a more comprehensive record of phytoplankton numbers, Boris Worm of Dalhousie University in Halifax, Canada, and colleagues dug into old shipboard records from sailors who had studied the ocean as far back as 1900. In those days, sailors used a tool called a Secchi disk to gauge how clear the ocean was. They weren’t trying to measure phytoplankton, but they inadvertently did because chlorophyll clouds the water.

When Worm and colleagues combined the satellite data, the early shipboard records, and direct measurements of chlorophyll made from the 1950s onward, they found that the recent dip in phytoplankton wasn’t a passing phase. It had been happening in most parts of the ocean for more than a century. On average, the planet has lost 1% of its phytoplankton every year since 1900, the team reports in the 29 July issue of Nature.

“You compound that over a century, this becomes a huge, huge decline,” says Paul Falkowski, an oceanographer at Rutgers University in New Brunswick, New Jersey, who was not part of the study. Indeed, Worm’s team estimates that phytoplankton numbers have plummeted 40% since 1950.

What’s more, the team found that phytoplankton numbers were more likely to dwindle in areas of the ocean that were warming, suggesting that climate change is responsible for the drop.

The loss of phytoplankton is a huge problem for marine food chains, says Worm, because every creature in the ocean either eats phytoplankton or eats other organisms that depend on it. If their numbers start to decrease, the populations of these species would drop as well. “The rest of the food web would basically contract,” he says.

Even more chilling to marine biologist Anthony Richardson of the University of Queensland in Australia is the potential impact on our atmosphere. The ocean absorbs 40% of the CO2 humans emit. Phytoplankton, in turn, convert that CO2 into oxygen or die and bury it at the bottom of the ocean. If the phytoplankton are disappearing, Richardson says, “the ocean as a carbon sink is declining, and what that means is ultimately more CO2 will stay in the atmosphere instead of being dissolved in the ocean.” That will translate into a warmer world, which will wipe out even more phytoplankton.

The study has its drawbacks. The older shipboard data weren’t collected with nearly as much regularity as the satellite data, notes marine biologist Mike Behrenfeld of Oregon State University, Corvallis. Still, marine biologist David Siegel of the University of California, Santa Barbara, says that given the sporadic records, Worm and colleagues have constructed a solid report. “They’ve squeezed as much as possibly can be squeezed out of this data set.”

via Critical Ocean Organisms Are Disappearing – ScienceNOW.