Are Honeybees Losing Their Way?

A single honeybee visits hundreds, sometimes thousands, of flowers a day in search of nectar and pollen. Then it must find its way back to the hive, navigating distances up to five miles (eight kilometers), and perform a "waggle dance" to tell the other bees where the flowers are.

A new study shows that long-term exposure to a combination of certain pesticides might impair the bee's ability to carry out its pollen mission.

"Any impairment in their ability to do this could have a strong effect on their survival," said Geraldine Wright, a neuroscientist at Newcastle University in England and co-author of a new study posted online February 7, 2013, in the Journal of Experimental Biology.

Wright's study adds to the growing body of research that shows that the honeybee's ability to thrive is being threatened. Scientists are still researching how pesticides may be contributing to colony collapse disorder (CCD), a rapid die-off seen in millions of honeybees throughout the world since 2006.

"Pesticides are very likely to be involved in CCD and also in the loss of other types of pollinators," Wright said. (See the diversity of pollinating creatures in a photo gallery from National Geographic magazine.)

Bees depend on what's called "scent memory" to find flowers teeming with nectar and pollen. Their ability to rapidly learn, remember, and communicate with each other has made them highly efficient foragers, using the waggle dance to educate others about the site of the food source.

Watch as National Geographic explains the waggle dance.

Their pollination of plants is responsible for the existence of nearly a third of the food we eat and has a similar impact on wildlife food supplies.

Previous studies have shown certain types of pesticides affect a bee's learning and memory. Wright's team wanted to investigate if the combination of different pesticides had an even greater effect on the learning and memory of honeybees.

"Honeybees learn to associate floral colors and scents with the quality of food rewards," Wright explained. "The pesticides affect the neurons involved in these behaviors. These [affected] bees are likely to have difficulty communicating with other members of the colony."

The experiment used a classic procedure with a daunting name: olfactory conditioning of the proboscis extension reflex. In layman's terms, the bee sticks out its tongue in response to odor and food rewards.

For the experiment, bees were collected from the colony entrance, placed in glass vials, and then transferred into plastic sandwich boxes. For three days the bees were fed a sucrose solution laced with sublethal doses of pesticides. The team measured short-term and long-term memory at 10-minute and 24-hour intervals respectively. (Watch of a video of a similar type of bee experiment.)

This study shows that when pesticides are combined, the impact on bees is far worse than exposure to just one pesticide. "This is particularly important because one of the pesticides we used, coumaphos, is a 'medicine' used to treat Varroa mites [pests that have been implicated in CCD] in honeybee colonies throughout the world," Wright said.

The pesticide, in addition to killing the mites, might also be making honeybees more vulnerable to poisoning and effects from other pesticides.

Stephen Buchmann of the Pollinator Partnership, who was not part of Wright's study, underscored how critical pollinators are for the world. "The main threat to pollinators is habitat destruction and alteration. We're rapidly losing pollinator habitats, natural areas, and food-producing agricultural lands that are essential for our survival and well being. Along with habitat destruction, insecticides weaken pollinators and other beneficial insects."

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'Blade Runner' Charged With Murdering Girlfriend

Oscar Pistorius, the Olympic and Paralympic athlete known as the "blade runner," was taken into custody in South Africa today and charged with the murder of his girlfriend, who was fatally shot at his home.

Police in the South African capital of Pretoria received a call around 3 a.m. today that there had been a shooting at the home of 26-year-old Pistorius, Lt. Col. Katlego Mogale told The Associated Press. When police arrived at the scene, they found paramedics trying to revive 29-year-old Reeva Steenkamp, the AP reported.

At a news conference early today, police said Pistorius was arrested and had requested that he be taken to court immediately.

PHOTOS:
Paralympic Champion Charged with Murder

Mogale said the woman died at the house, and a 9-mm pistol was recovered at the scene and a murder case opened against Pistorius, the AP reported.

Police said this morning that there were no other suspects in the shooting, and that Pistorius is at the police station.

Adrian Dennis/AFP/Getty Images; Mike Holmes/The Herald/Gallo Images/Getty Images

Oscar Pistorius: Double Amputee Going to Olympics Watch Video

Valentine's Day Is All About the Men in Japan Watch Video

The National Prosecuting Authority (NPA) said Pistorius' hearing will be Friday at 9 a.m. local time. His court hearing was originally scheduled for this afternoon but has been postponed to give forensics investigators time to carry out their work, NPA spokesman Medupe Simasiku said.

The precise circumstances surrounding the incident are unclear. Local reports say he might have mistaken her for a burglar, according to the AP.

VIDEO: Double Amputee Races to Win Olympic Gold

Police said they have heard reports of an argument or shouting at the apartment complex, and that the only two people on the premises were Steenkamp and Pistorius.

Police confirmed there have previously been incidents of a domestic nature at the home of Pistorius.

Pistorius, a sprinter, had double below-the-knee amputations and a part of his legs has been replaced with carbon fiber blades. In 2012, he became the first double-leg amputee to participate in the Olympics, competing in the men's 400-meter race.

He also competed in the Paralympics, where he won gold medals in the men's 400-meter race, in what became a Paralympics record. He also took the silver in the 200-meter race.

Steenkamp, according to her Twitter bio, is a law graduate and model. She tweeted Wednesday, "What do you have up your sleeve for your love tomorrow??? #getexcited #ValentinesDay."

Steenkamp recently appeared on the cover of FHM magazine, in commercials and was due to appear on a reality-TV show, "Tropika Island of Treasure."

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Obama urges a move away from narrow focus on politics of austerity

Just about every argument in Washington since the 2010 midterm elections, which returned control of the House to Republicans, has centered on reducing the federal deficit. On Tuesday night, President Obama leaned into his second term by declaring that a single-minded focus on deficit reduction would jeopardize the nation’s future. And he sounded an urgent call to rebuild.

Reelected by an ascendent coalition, the president spoke from a position of strength in his fourth State of the Union address. The economy is improving. The Republican Party is in disarray. The time has come, Obama indicated, to pivot away from the politics of austerity.

“Most of us agree that a plan to reduce the deficit must be part of the agenda,” he said. “But let’s be clear: Deficit reduction alone is not an economic plan. A growing economy that creates good middle-class jobs — that must be the North Star that guides our efforts.”

The president rejected the fiscal brinkmanship that defined the past two years. Instead, he framed future fiscal debates as opportunities to shape a “smarter government” — one with new investments in science and innovation, with a rising minimum wage, with tax reform that eliminates loopholes and deductions for what the president labeled “the well-off and well-connected.”

Second-term presidents have a narrow window of time to enact significant change before they become lame ducks, and Obama, while echoing campaign themes of reinforcing the middle class, made an urgent case for a more pragmatic version of populism, one that emphasizes economic prosperity as the cornerstone of a fair society.

Over and over, he noted that the time to rebuild is now.

The “Fix-It-First” program that Obama outlined to put people to work on “urgent repairs,” such as structurally deficient bridges, bore echoes of President Bill Clinton’s call in his 1999 State of the Union address to “save Social Security first.” Clinton’s was an effective line, one that stopped — at least until President George W. Bush took office two years later — a Republican drive to use the budget surplus to cut taxes.

Although Obama’s speech lacked the conciliatory notes of some of his earlier State of the Union addresses, he did make overtures to Republicans and cited Mitt Romney, his presidential challenger, by name.

He combined tough talk about securing the border, which brought Republicans to their feet, with a pledge to entertain reasonable reforms to Medicare, the federal entitlement program that fellow Democrats are fighting to protect.

“Those of us who care deeply about programs like Medicare must embrace the need for modest reforms,” he said.

Obama also pledged to cut U.S. dependence on energy imports by expanding oil and gas development. And he singled out one area where he and Romney found agreement in last year’s campaign: linking increases in the minimum wage to the cost of living.

Obama set a bipartisan tone at the start of his speech, quoting from President John F. Kennedy’s address to Congress 51 years earlier when he said, “The Constitution makes us not rivals for power, but partners for progress.”

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Olympics: Wrestlers vow to fight Olympic removal

PARIS: Wrestlers around the world on Wednesday vowed to fight to save the ancient sport's Olympic status, after the International Olympic Committee voted to drop it for the 2020 Games.

Japan and Turkey -- whose cities Tokyo and Istanbul are bidding to host the Games in seven years' time -- led the calls for the world body to reconsider, as an online petition was organised urging a rethink and gained thousands of supporters.

The president of the Turkish wrestling federation, Hamza Yerlikaya, called the decision, taken at the IOC executive board meeting in Lausanne, Switzerland, on Tuesday, "unfair" and a "mistake" that they would seek to overturn.

"To have the 2020 Olympics in Istanbul without wrestling is unthinkable," said Yerlikaya, himself a double Olympic gold medallist, three-time world champion and eight-time European champion in Greco-Roman wrestling.

"We won't allow it," he added.

In Japan, Yerlikaya's counterpart Tomiaki Fukuda said on his federation's website that he was "dissatisfied and baffled", echoing the views of the sport's world governing body, which called the decision "an aberration".

Wrestling will remain on the programme for the 2016 Olympics in Rio de Janeiro but faces a fight against seven other sports for inclusion at the Games four years later. A final decision is to be made when all IOC members meet in September.

Members are seen as unlikely to vote against the executive board, however, raising the prospect that one of the few sports that survived from the original Olympics in ancient Greece into the modern era will disappear.

Wrestling first appeared in 708 BC and has only ever been left out of the Olympic programme once before in 1900.

The International Federation of Associated Wrestling Styles (FILA) has vowed to fight the decision, while multiple medallists Russia and Iran have also said they hoped the IOC would backtrack.

"This issue will definitely be a big blow to the country's sport, as it is one of our country's most popular sports," the head of Iran's national Olympic commitee, Mohammad Aliabadi was quoted as saying in Iranian media, "I will certainly pursue the case."

IOC president Jacques Rogge meanwhile insisted on Wednesday that the vote -- by secret ballot -- was fair and said he understood the angry response from those involved in the sport.

A meeting was planned between the committee and the International Federation of Associated Wrestling Styles (FILA), to discuss the matter, he told a news conference in Lausanne.

Wrestlers have been left dismayed by the decision, with Japan's undisputed queen of the ring, Saori Yoshida, saying: "I am so devastated that I don't know what to do."

Yoshida, a 55kg-class freestyle wrestler who is the face of Tokyo's campaign for the right to host the 2020 Games, has won a record 13 straight Olympic and world championship gold medals over 10 years.

In India, Sushil Kumar, who won a bronze in Beijing and a silver in London last year, said: "I still can't get over the news that we won't be at the Olympics.

"All sportsmen look towards the Olympics as the pinnacle of excellence, everyone wants to take part in them. Now what do we do? Give up wrestling? I hope the IOC will reconsider this decision."

An online petition at change.org entitled "The International Olympic Committee: Save Wrestling as an Olympic sport #SaveOlympicWrestling" has also been mounted, urging the US Senate to take up the matter.

By late afternoon on Wednesday, it had more than 21,000 signatures.

On Twitter, one user, @WrestlersLoveUs, wrote: "Ancient Olympic wrestlers used to sometimes fight to the death. IOC better understand we're ready to do that again. #SaveOlympicWrestling."

-AFP/fl

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Afzal Guru's family lawyers quit

NEW DELHI: Citing "unseemly controversies", ND Pancholi and Nandita Haksar Wednesday quit as the family lawyers of Afzal Guru, the parliament attack convict who was hanged here Feb 9.

"There have arisen unseemly controversies and we do not wish to be part of these discussions," Pancholi and Haksar said in a statement.

The duo were representing Guru's family members who have asked Tihar jail authorities to return them Guru's body buried inside the prison premises.

Pancholi and Haksar said they did not belong to any political party. However, they believed in engagement with the institutions and were working through them because there was no alternative, the statement said.

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Obama Pledges U.S. Action on Climate, With or Without Congress

If there were anything in President Barack Obama's State of the Union to give hope to wistful environmentalists, it was the unprecedented promise to confront climate change with or without Congress, and to pursue new energy technology in the process.

Following his strong statements in his inaugural address about the ripeness of the moment to address a changing climate, Obama outlined a series of proposals to do it. Recognizing that the 12 hottest years on record all occurred in the last decade and a half, Obama said his most ambitious goal would be a "bipartisan, market-based solution," similar to the cap-and-trade system that died in Congress during his first term.(See related story: "California Tackles Climate Change, But Will Others Follow?")

But without legislative action, Obama threatened to act himself using executive authority. "I will direct my Cabinet to come up with executive actions we can take, now and in the future, to reduce pollution, prepare our communities for the consequences of climate change, and speed the transition to more sustainable sources of energy," he said. That will translate, White House officials said earlier in the week, to new regulations for existing coal-burning power plants and directives to promote energy efficiency and new technology research. (See related story: "How Bold a Path on Climate Change in Obama's State of the Union?")

The effort isn't one that can be stalled, he noted. Not just because of a warming planet, but also because of international competition from countries like China and parts of Western Europe that have gone "all in" on clean energy.

Energy experts signaled support of Obama's comments on energy security, including a plan for an Energy Security Trust to use revenue from oil and gas production on public lands to fund new energy research. "Clean energy businesses commend the president for reaffirming his commitment to reduce greenhouse gas emissions and to address the damaging and costly impacts of climate change," Lisa Jacobson, president of Business Council for Sustainable Energy, said in a statement. The influential League of Conservation Voters perked up to Obama's vow to act on climate change, even if alone.

Noticeably unmentioned in the speech was the Keystone XL pipeline that would carry oil from Canadian tar sands to the refining centers of Texas. Environmentalists have urged Obama to reject the project's application for federal approval in order to hold the line against carbon-intensive production from the oil sands. (See related blog post: "Obama and Keystone XL: The Moment of Truth?") Energy analysts believe Obama is likely to approve the project in the coming weeks, yet at the same time offer new regulations on domestic oil and natural gas development.

Other environmental analysts took Obama's remarks as simple talk, so far not backed by action. “How many times do we have to have the problem described?” David Yarnold, president of the Audubon Society said after the speech. “Smarter standards for coal-fired power plants are the quickest path to a cleaner future, and the president can make that happen right now.”

Obama's path toward accomplishing those goals will likely be lonely. In the Republican rebuttal to Obama's speech, Florida Senator Marco Rubio sidelined climate change as an issue of concern and highlighted the deep partisan distrust. "When we point out that no matter how many job-killing laws we pass, our government can’t control the weather, he accuses us of wanting dirty water and dirty air," Rubio said. He echoed the long-held Republican concern that remaking an economy may not be the wisest way to confront the problem of extreme weather.

Central to Obama's efforts will be his nominees to lead the Environmental Protection Agency and the Department of Energy in his second term. Both roles were at times attacked over his first term, notably when EPA instituted new air and water regulations and DOE was caught making a bad investment in the now-defunct solar manufacturer Solyndra. If the tone of his State of the Union offers a blueprint, he'll choose people unafraid to act.

This story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.

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Charred Human Remains Found in Burned Cabin

Investigators have located charred human remains in the burned-out cabin where they believe suspected cop killer and ex-LAPD officer Christopher Dorner was holed up as the structure burned to the ground, police said.

The human remains were found within the debris of the burned cabin and identification will be attempted through forensic means, the San Bernardino County Sheriff-Coroner Department said in a news release early this morning.

Dorner barricaded himself in the cabin in the San Bernardino Mountains near Big Bear Tuesday afternoon after engaging in a gunfight with police, killing one officer and injuring another, the San Bernardino County Sheriff's Department said.

Cindy Bachman, a spokeswoman for the department, which is the lead agency in the action, said Tuesday night investigators would remain at the site all night.

FULL COVERAGE: Christopher Dorner Manhunt

When Bachman was asked whether police thought Dorner was in the burning cabin, she said, "Right. We believe that the person that barricaded himself inside the cabin engaged in gunfire with our deputies and other law enforcement officers is still inside there, even though the building burned."

Bachman spoke shortly after the Los Angeles Police Department denied earlier reports that a body was found in the cabin, contradicting what law enforcement sources told ABC News and other news organizations.

Police around the cabin told ABC News they saw Dorner enter but never leave the building as it was consumed by flames, creating a billowing column of black smoke seen for miles.

A news conference is scheduled for later today in San Bernardino.

One sheriff's deputy was killed in a shootout with Dorner earlier Tuesday afternoon, believed to be his fourth victim after killing a Riverside police officer and two other people this month, including the daughter of a former police captain, and promising to kill many more in an online manifesto.

PHOTOS: Former LAPD Officer Suspected in Shootings

Carjacking Victim Says Christopher Dorner Was Dressed for Damage Watch Video

Christopher Dorner Manhunt: Inside the Shootout Watch Video

Chris Dorner Manhunt: Fugitive Ex-Cop in Shootout With Police Watch Video

Cops said they heard a single gunshot go off from inside the cabin just as they began to see smoke and fire. Later they heard the sound of more gunshots, which was the sound of ammunition being ignited by the heat of the blaze, law enforcement officials said.

Police did not enter the building, but shot tear gas inside.

One of the largest dragnets in recent history, which led police to follow clues across the West and into Mexico, apparently ended just miles from where Dorner's trail went cold last week.

It all began at 12:20 p.m. PT Tuesday, when a maid working at a local resort called 911, saying she and another worker had been tied up and held hostage by Dorner in a cabin, sources said.

The maid told police she was able to escape, but Dorner had stolen one of their cars, which was identified as a purple Nissan.

The San Bernardino Sheriff's Office and state Fish and Wildlife wardens spotted the stolen vehicle and engaged in a shootout with Dorner.

Officials say Dorner crashed the stolen vehicle and fled on foot only to commandeer Rick Heltebrake's white pickup truck on a nearby road a short time later.

"[Dorner] said, 'I don't want to hurt you, just get out and start walking up the road and take your dog with you.' He was calm. I was calm. I would say I was in fear for my life, there was no panic, he told me what to do and I did it," Heltebrake said.

"He was dressed in all camouflage, had a big assault sniper-type rifle. He had a vest on like a ballistic vest," Heltebrake added.

The white pickup truck bought Dorner extra time because police were still looking for the purple Nissan, California Department of Fish and Wildlife Lt. Patrick Foy told "Good Morning America" today.

"We were looking for a purple color Nissan and all of a sudden this white pickup starts coming by in the opposite direction. That's not the suspect's vehicle that we had been looking for," Foy said.

A warden with the Fish and Wildlife department noticed Dorner driving and the pursuit picked up again, Foy said.

"Ultimately, the officer who was driving that vehicle stopped and pulled out his patrol rifle and engaged probably 15 to 20 shots as Dorner was driving away," Foy said.

Dorner then ran on foot to the cabin in which he barricaded himself and got in a shootout with San Bernardino County sheriff's deputies and other officers who arrived.

The two deputies were wounded in the firefight and airlifted to a nearby hospital, where one died, police said. The second deputy was in surgery and was expected to survive, police said.

Police sealed all the roads into the area, preventing cars from entering the area and searching all of those on the way out. All schools were briefly placed on lockdown.

Believing that Dorner might have been watching reports of the standoff, authorities asked media not to broadcast images of police officers' surrounding the cabin, but sent him a message.

"If he's watching this, the message is: Enough is enough," Los Angeles Police Department spokesman Andy Smith told reporters at a news conference Tuesday. "It's time to turn yourself in. It's time to stop the bloodshed. It's time to let this event and let this incident be over."

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Tension running high in Kashmir Valley

KASHMIR VALLEY: Tension is running high in Kashmir Valley, after India's secret execution of a Kashmiri man for his involvement in an attack on parliament in 2001.

A continuous curfew has been in place for four days now, as the government attempts to prevent further outbreaks of violence.

The curfew has brought life to a standstill in the valley.

Three people have died and at least 50 others injured in protests over India's execution of a Kashmiri militant, Afzal Guru, on February 9.

Farooq Ahmed, a resident, said: "This curfew isn't right. Even if someone is sick, the police won't let them leave. Yesterday, there was some stone pelting -- if someone got injured... it's not right. The curfew is making life very difficult for people."

While the police keep a strict vigil, making sure there is no movement on the streets, opposition leaders are speaking out against such extreme measures.

Mehbooba Mufti, an opposition leader from the People's Democratic Party, said: "What has happened is very bad. The consequence of this will negatively impact the psyche of the young generation."

It could take many days before life returns to normal in the valley.

For now, the Kashmir government may succeed in containing the situation.

However, there is still a considerable chance that violence could still break out. And that is not something the state government would look forward to, especially when things were beginning to return to normal after years of conflict.

- CNA/al

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Govt shuffles key diplomatic pack

NEW DELHI: After months of administrative silence, the government has cleared key ambassadorial appointments. Ashoke Mukherji is likely to be India's next Permanent Representative (PR) to the UN, taking over from Hardeep Singh Puri, who retires in end-February after two years of steering India through a rare stint in the UN Security Council. Arun Singh is likely to take over as India's ambassador to France.

Singh has been second-in command in Washington for the past four years, overseeing crucial bilateral ties during the first Obama administration after being envoy to Israel. He will be replacing Rakesh Sood, who has been given a one-month extension to tide over the French president Francois Hollande's maiden visit to India. The bilateral and strategic relationship with France has improved significantly in recent years, with France emerging as the top supplier for nuclear reactors as well as combat aircraft. French Rafale won the contract for India's biggest ever defence deal of 126 MMRCA.

Pakistan will see a changeover, with India's High Commissioner Sharat Sabharwal making way for T C A Raghavan, currently envoy to Singapore. Raghavan has been the head of the territorial division in charge of Pakistan in the ministry of external affairs (MEA), besides serving in Islamabad. He is also known to be a trusted hand for national security advisor (NSA) Shivshankar Menon. Vijay Thakur Singh is slated to take over from Raghavan in Singapore.

Gautam Mukhopadhyay, India's envoy in Kabul, may take over an equally-sensitive portfolio as ambassador to Myanmar. Former governor of West Bengal Gopal Gandhi had reportedly written a letter to the Prime Minister requesting for the post because he had been impressed by Aung San Suu Kyi. Among the MEA mavens, there was little appetite to indulge this request because Myanmar needs skillful professional handling.

This year will also see big changes in the MEA as the ministry gets ready to shop for its next foreign secretary. The post of ambassador to the US will fall vacant soon, though there are rumours that Nirupama Rao might get an extension. London is likely to fall vacant later this year along with The Hague and Berlin. In the immediate neighborhood, the volatile Maldives will be seeing a new High Commissioner after India's controversial envoy, D N Mulay, moves to New York. Rajeev Shahare, joint secretary in the MEA, is slated to take his place. S Jaishankar, India's ambassador to China, is slated to return as well, which could see a movement in Sri Lanka or Malaysia, both of which have expert China hands heading Indian missions.

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What Killed Dinosaurs: New Ideas About the Wipeout

New insights about the asteroid thought to have killed off the dinosaurs suggest it may have just been the final blow, and that the reptiles were already suffering from a finicky climate prompted by volcanic eruptions long before the meteorite struck.

"The [asteroid] impact was the coup de grace," Paul Renne, a geologist at the University of California, Berkeley, said in a statement.

The research, detailed in the February 8 issue of the journal Science, adds to the ongoing scientific debate over what exactly killed off the dinosaurs.

That debate, which once revolved around the question of whether the culprit was an asteroid or volcano-induced climate changes, has evolved to consider the possibility that perhaps multiple environmental factors were involved.

Renne and his team recently determined the most precise date yet for the asteroid strike, which occurred in the Yucatan peninsula in what is now Mexico.

Using a high-precision dating technique on tektites—pebble-sized rocks formed during meteorite impacts—from Haiti that were created during the event, the team concluded that the impact occurred 66,038,000 years ago—slightly later than previously thought.

When error limits are taken into account, the new date is the same as the date of the extinction, the team says, making the events simultaneous.

Renne said the new findings, should lay to rest any remaining doubts about whether an asteroid was a factor in the dinosaurs' demise.

"We have shown that these events are synchronous to within a gnat's eyebrow," he said, "and therefore the impact clearly played a major role in extinctions."

That is not to say, however, that the asteroid—which carved out the so-called Chicxulub crater—was the sole cause of the dinosaurs' extinction.

Evidence now suggests massive volcanic eruptions in India that predated the asteroid strike also played a part, triggering climate changes that were already killing off some dinosaur groups.

For example, "nobody has ever found a non-avian dinosaur fossil exactly at the impact layer," Renne said in an email. "Hence, strictly speaking, the non-avian dinosaurs"—those dinosaurs unrelated to birds—"may have already gone extinct by the time of the impact."

Death From the Skies

The idea that volcanism was responsible for the dinosaurs' demise actually predates the impact theory, and it fits well with what is known about Earth's other mass extinction events.

"Many of the other mass extinctions have been found to co-occur with large-scale volcanic eruptions," said Heiko Pälike, a paleoceanographer at the University of Bremen in Germany.

But in the 1980s, father-son team Luis and Walter Alvarez, a physicist and planetary scientists, respectively, presented a bold new theory.

After discovering that a layer of clay that's found throughout the world and that coincided with the end of the Cretaceous period is enriched in iridium—an element rare on Earth but common in space rocks—they proposed that a meteorite wiped out the dinosaurs.

"As the impact theory took hold, especially with the more physical scientists ... the volcanists lost ground," Renne explained.

The impact theory gained further momentum in the 1990's, when scientists discovered a 110-mile (180-kilometer) wide impact crater in the Yucatan peninsula that dated to the boundary between the Cretaceous and Tertiary periods—the so-called KT boundary—when the dinosaurs disappeared.

The crater's size indicated that whatever created it was roughly 6 miles (10 kilometers) in diameter.

An asteroid of that size striking the Earth would have had devastating consequences, including destructive pressure waves, global wildfires, tsunamis, and a "rain" of molten rock reentering the atmosphere.

Additionally, "much additional particulate matter would have stayed afloat in the atmosphere for weeks, months, perhaps years, blocking incoming solar radiation and thus killing plant life and causing catastrophic drops in temperatures," explained Hans-Dieter Sues, a paleontologist at the Smithsonian National Museum of Natural History in Washington, D.C.

Hybrid Theory for Dinosaur Extinction

The once-abandoned volcanism theory has seen a revival of sorts in recent years, however, as a result of fresh insights about a period of sustained ancient volcanic activity in India and the discovery that dinosaur diversity may have already been declining before the asteroid strike.

The debate now is "whether the Chicxulub impact was the 'smoking gun,' as many researchers claim," Sues said, "or one of several causative factors, kind of like 'Murder on the Orient Express.'"

Renne belongs to the camp that thinks a series of volcanic eruptions in India that produced ancient lava flows known as the Deccan Traps caused dramatic climate variations, including long cold snaps, that may have already been culling the dinosaurs before the asteroid struck.

"It seems clear that volcanism alone, if on a sufficiently massive and rapid scale, can trigger extinctions," Renne said. "Thus my view that the impact was probably the final straw, but not the sole cause."

Unanswered questions

The new hybrid theory still has some major questions it must answer, however, like precisely how much the Indian volcanic eruptions affected the dinosaurs.

"Some people say if you look at the eruption of Mount Pinatubo [in 1991], it cooled the Earth for a short period of time due to the aerosol and the dust that was ejected," Pälike said.

But "others say in the long run volcanoes probably pump more carbon dioxide into the atmosphere and actually warm the planet, at least temporarily."

It's also unclear how the Deccan Traps eruptions were spread out in time. "We know that they started a few million years before the end of the Cretaceous and lasted for several million years after, extending even beyond the [asteroid impact]," Pälike said.

"However, some people have suggested that there were clusters of eruptions that happened within a span of a few tens of thousands of years."

Knowing the timing of the eruptions is important, Pälike added, because if they were happening close to the end of the Cretaceous, it's more likely they played a role in the dinosaurs' extinction than if most of the eruptions happened two million years before.

Pälike thinks that more precise dating of the volcanic ash layers in India could help answer some of the remaining questions: "That's the next step of the puzzle."

Pinning down the cause of the dinosaurs' extinction isn't just of academic interest, said Jonathan Bloch, associate curator of vertebrate paleontology at the Florida Museum of Natural History at the University of Florida.

"It's important for us to understand how ecosystems respond to big perturbations," Bloch said, "whether it's gradual climate change or a catastrophic event. These are all things we have to think about as humans on the planet today."

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