ENIGMA Molten glass being worked into an ornament. Understanding glass could lead to better products and offer headway in other scientific problems.
By Kenneth Chang, July 29, 2008, The New York Times – It is well known that panes of stained glass in old European churches are thicker at the bottom because glass is a slow-moving liquid that flows downward over centuries.
Well known, but wrong. Medieval stained glass makers were simply unable to make perfectly flat panes, and the windows were just as unevenly thick when new.
The tale contains a grain of truth about glass resembling a liquid, however. The arrangement of atoms and molecules in glass is indistinguishable from that of a liquid. But how can a liquid be as strikingly hard as glass?
“They’re the thickest and gooiest of liquids and the most disordered and structureless of rigid solids,” said Peter Harrowell, a professor of chemistry at the University of Sydney in Australia, speaking of glasses, which can be formed from different raw materials. “They sit right at this really profound sort of puzzle.”
Philip W. Anderson, a Nobel Prize-winning physicist at Princeton, wrote in 1995: “The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition.”
He added, “This could be the next breakthrough in the coming decade.”
Thirteen years later, scientists still disagree, with some vehemence, about the nature of glass.
Bloomberg News, top, and Keystone/Corbis
COMPLEX Glass in sheet and molten forms. Glass transition differs from usual phase transition.
Peter G. Wolynes, a professor of chemistry at the University of California, San Diego, thinks he essentially solved the glass problem two decades ago based on ideas of what glass would look like if cooled infinitely slowly. “I think we have a very good constructive theory of that these days,” Dr. Wolynes said. “Many people tell me this is very contentious. I disagree violently with them.”
Others, like Juan P. Garrahan, professor of physics at the University of Nottingham in England, and David Chandler, professor of chemistry at the University of California, Berkeley, have taken a different approach and are as certain that they are on the right track.
“It surprises most people that we still don’t understand this,” said David R. Reichman, a professor of chemistry at Columbia, who takes yet another approach to the glass problem. “We don’t understand why glass should be a solid and how it forms.”
Dr. Reichman said of Dr. Wolynes’s theory, “I think a lot of the elements in it are correct,” but he said it was not a complete picture. Theorists are drawn to the problem, Dr. Reichman said, “because we think it’s not solved yet — except for Peter maybe.”
Scientists are slowly accumulating more clues. A few years ago, experiments and computer simulations revealed something unexpected: as molten glass cools, the molecules do not slow down uniformly. Some areas jam rigid first while in other regions the molecules continue to skitter around in a liquid-like fashion. More strangely, the fast-moving regions look no different from the slow-moving ones.
Meanwhile, computer simulations have become sophisticated and large enough to provide additional insights, and yet more theories have been proffered to explain glasses.
David A. Weitz, a physics professor at Harvard, joked, “There are more theories of the glass transition than there are theorists who propose them.” Dr. Weitz performs experiments using tiny particles suspended in liquids to mimic the behavior of glass, and he ducks out of the theoretical battles. “It just can get so controversial and so many loud arguments, and I don’t want to get involved with that myself.”
For scientists, glass is not just the glass of windows and jars, made of silica, sodium carbonate and calcium oxide. Rather, a glass is any solid in which the molecules are jumbled randomly. Many plastics like polycarbonate are glasses, as are many ceramics.
Understanding glass would not just solve a longstanding fundamental (and arguably Nobel-worthy) problem and perhaps lead to better glasses. That knowledge might benefit drug makers, for instance. Certain drugs, if they could be made in a stable glass structure instead of a crystalline form, would dissolve more quickly, allowing them to be taken orally instead of being injected. The tools and techniques applied to glass might also provide headway on other problems, in material science, biology and other fields, that look at general properties that arise out of many disordered interactions.
“A glass is an example, probably the simplest example, of the truly complex,” Dr. Harrowell, the University of Sydney professor, said. In liquids, molecules jiggle around along random, jumbled paths. When cooled, a liquid either freezes, as water does into ice, or it does not freeze and forms a glass instead.
In freezing to a conventional solid, a liquid undergoes a so-called phase transition; the molecules line up next to and on top of one another in a simple, neat crystal pattern. When a liquid solidifies into a glass, this organized stacking is nowhere to be found. Instead, the molecules just move slower and slower and slower, until they are effectively not moving at all, trapped in a strange state between liquid and solid.
The glass transition differs from a usual phase transition in several other key ways. It takes energy, what is called latent heat, to line up the water molecules into ice. There is no latent heat in the formation of glass.
The glass transition does not occur at a single, well-defined temperature; the slower the cooling, the lower the transition temperature. Even the definition of glass is arbitrary — basically a rate of flow so slow that it is too boring and time-consuming to watch. The final structure of the glass also depends on how slowly it has been cooled.
By contrast, water, cooled quickly or cooled slowly, consistently crystallizes to the same ice structure at 32 degrees Fahrenheit.
To develop his theory, Dr. Wolynes zeroed in on an observation made decades ago, that the viscosity of a glass was related to the amount of entropy, a measure of disorder, in the glass. Further, if a glass could be formed by cooling at an infinitely slow rate, the entropy would vanish at a temperature well above absolute zero, violating the third law of thermodynamics, which states that entropy vanishes at absolute zero.
Dr. Wolynes and his collaborators came up with a mathematical model to describe this hypothetical, impossible glass, calling it an “ideal glass.” Based on this ideal glass, they said the properties of real glasses could be deduced, although exact calculations were too hard to perform. That was in the 1980s. “I thought in 1990 the problem was solved,” Dr. Wolynes said, and he moved on to other work.
Not everyone found the theory satisfying. Dr. Wolynes and his collaborators so insisted they were right that “you had the impression they were trying to sell you an old car,” said Jean-Philippe Bouchaud of the Atomic Energy Commission in France. “I think Peter is not the best advocate of his own ideas. He tends to oversell his own theory.”
Around that time, the first hints of the dichotomy of fast-moving and slow-moving regions in a solidifying glass were seen in experiments, and computer simulations predicted that this pattern, called dynamical heterogeneity, should exist.
Dr. Weitz of Harvard had been working for a couple of decades with colloids, or suspensions of plastic spheres in liquids, and he thought he could use them to study the glass transition. As the liquid is squeezed out, the colloid particles undergo the same change as a cooling glass. With the colloids, Dr. Weitz could photograph the movements of each particle in a colloidal glass and show that some chunks of particles moved quickly while most hardly moved.
“You can see them,” Dr. Weitz said. “You can see them so clearly.”
The new findings did not faze Dr. Wolynes. Around 2000, he returned to the glass problem, convinced that with techniques he had used in solving protein folding problems, he could fill in some of the computational gaps in his glass theory. Among the calculations, he found that dynamical heterogeneity was a natural consequence of the theory.
Dr. Bouchaud and a colleague, Giulio Biroli, revisited Dr. Wolynes’s theory, translating it into terms they could more easily understand and coming up with predictions that could be compared with experiments. “For a long time, I didn’t really believe in the whole story, but with time I became more and more convinced there is something very deep in the theory,” Dr. Bouchaud said. “I think these people had fantastic intuition about how the whole problem should be attacked.”
For Dr. Garrahan, the University of Nottingham scientist, and Dr. Chandler, the Berkeley scientist, the contrast between fast- and slow-moving regions was so striking compared with the other changes near the transition, they focused on these dynamics. They said that the fundamental process in the glass transition was a phase transition in the trajectories, from flowing to jammed, rather than a change in structure seen in most phase transitions. “You don’t see anything interesting in the structure of these glass formers, unless you look at space and time,” Dr. Garrahan said.
They ignore the more subtle effects related to the impossible-to-reach ideal glass state. “If I can never get there, these are metaphysical temperatures,” Dr. Chandler said.
Dr. Chandler and Dr. Garrahan have devised and solved mathematical models, but, like Dr. Wolynes, they have not yet convinced everyone of how the model is related to real glasses. The theory does not try to explain the presumed connection between entropy and viscosity, and some scientists said they found it hard to believe that the connection was just coincidence and unrelated to the glass transition.
Dr. Harrowell said that in the proposed theories so far, the theorists have had to guess about elementary atomic properties of glass not yet observed, and he wondered whether one theory could cover all glasses, since glasses are defined not by a common characteristic they possess, but rather a common characteristic they lack: order. And there could be many reasons that order is thwarted. “If I showed you a room without an elephant in the room, the question ‘why is there not an elephant in the room?’ is not a well-posed question,” Dr. Harrowell said.
New experiments and computer simulations may offer better explanations about glass. Simulations by Dr. Harrowell and his co-workers have been able to predict, based on the pattern of vibration frequencies, which areas were likely to be jammed and which were likely to continue moving. The softer places, which vibrate at lower frequencies, moved more freely.
Mark D. Ediger, a professor of chemistry at the University of Wisconsin, Madison, has found a way to make thin films of glass with the more stable structure of a glass that has been “aged” for at least 10,000 years. He hopes the films will help test Dr. Wolynes’s theory and point to what really happens as glass approaches its ideal state, since no one expects the third law of thermodynamics to fall away.
Dr. Weitz of Harvard continues to squeeze colloids, except now the particles are made of compressible gels, enabling the colloidal glasses to exhibit a wider range of glassy behavior.
“When we can say what structure is present in glasses, that will be a real bit of progress,” Dr. Harrowell said. “And hopefully something that will have broader implications than just the glass field.”
July 29, 2008
Stephen M. Meyer
Dr. Stephen M. Meyer, who died recently, was a professor of political science at MIT and the director of the MIT Project on Environmental Politics and Policy.
For the past several billion years evolution on Earth has been driven by small-scale incremental forces such as sexual selection, punctuated by cosmic-scale disruptions—plate tectonics, planetary geochemistry, global climate shifts, and even extraterrestrial asteroids. Sometime in the last century that changed. Today the guiding hand of evolution is unmistakably human, with earth-shattering consequences.
The fossil record and statistical studies suggest that the average rate of extinction over the past hundred million years has hovered at several species per year. Today the extinction rate surpasses 3,000 species per year and is accelerating rapidly—it may soon reach the tens of thousands annually. In contrast, new species are evolving at a rate of less than one per year.
Over the next 100 years or so as many as half of the Earth’s species, representing a quarter of the planet’s genetic stock, will either completely or functionally disappear. The land and the oceans will continue to teem with life, but it will be a peculiarly homogenized assemblage of organisms naturally and unnaturally selected for their compatibility with one fundamental force: us. Nothing—not national or international laws, global bioreserves, local sustainability schemes, nor even “wildlands” fantasies—can change the current course. The path for biological evolution is now set for the next million years. And in this sense “the extinction crisis”—the race to save the composition, structure, and organization of biodiversity as it exists today—is over, and we have lost. . . .
Stephen M. Meyer is a professor of political science at MIT and the director of the MIT Project on Environmental Politics and Policy.
What kind of tree should I plant in my back yard to soak up the most carbon
My husband and I intend to plant some trees on our property this spring. We’d like to do our part in the fight against climate change, so we’re looking for trees that can sequester exceptionally large amounts of carbon. Can you recommend a specific species, one that’s the acknowledged champ at reducing greenhouse gases?
By Brendan I. Koerner, January 8, 2008, SLATE.com – The Lantern wishes he could just name a single species that will meet your needs, thereby making this his easiest (and shortest) column. But alas, there’s no one-size-fits-all answer to your query; the type of tree that’s best for the environment will depend on your geographic location and its attendant climate, as well as the composition of the soil on your property. And to maximize your results, you’ll have to commit to taking extra-special care of your trees during their formative years—and consider turning them into chairs or tables before they start to decay.
The first part of the sequestration equation is a no-brainer: The bigger a tree, the more room it has to store carbon. According to the United States Forest Service, the best trees for carbon sequestration are those with large trunk diameters and dense wood. It also helps if the trees sport leaves in lieu of needles; choose a hardwood over a conifer.
Just as important as maximum size and leaf type, however, is rate of growth—the faster a tree grows, the greater the percentage of its life that’s spent as an arborous titan. According to the Energy Information Administration, a 30-year-old hardwood that’s classified as a speedy grower—a red mulberry, for example, or a laurel oak—will sequester an average of 69.5 pounds of carbon per year, versus 36.8 pounds for a hardwood whose growth rate is deemed only moderate, and a measly 16.8 pounds for a true slowpoke.
Unfortunately, bigger hardwoods often grow at a snail’s pace, especially in northern climes where there’s a dearth of sunlight and chilly winters to contend with. As such, the conventional wisdom has long been that trees planted in equatorial rainforests are much better at stemming global warming than those planted in, say, Alberta or Vermont—the logic being that warm temperatures and heavy rainfall will result in faster average growth.
But North American trees can be goosed to grow more rapidly, a task usually accomplished through the careful application of nitrogen-based fertilizers. The downside to this method, however, is that the use of such fertilizers results in increased emissions of nitrous oxide, a potent greenhouse gas. A cleaner approach may be to plant a mix of trees—some that are good at sequestering carbon, others that enrich the soil by depositing nitrogen. Studies (PDF) on eucalyptus plantations, for example, have shown that more carbon is sequestered overall when nitrogen-fixing mimosa trees are added to the land.
If you’re planting a non-native species, your rate of growth may be lackluster no matter how much nitrogen you add to the soil. Do some research and find out which large, leafy, fast-growing hardwoods are native to your area. Native trees are also more likely to reach maturity and thrive for years.
Yet even the hardiest native trees are doomed to die someday, and in doing so, spew their carbon back into the atmosphere. (That’s particularly bad news when the trees are killed as part of a timber company’s clear-cutting efforts, since no young trees are left behind to help mitigate the losses.) If you’re around to witness your trees’ twilight years, consider keeping the carbon in place by turning them into furniture or building lumber, rather than letting them go gently into that good night.
OK, so let’s say you don’t have the inclination to research the perfect tree for your locale, nor the time to spend ensuring that your soil is suitably flush with nitrogen. If that’s the case with you and your husband, you probably can’t go too terribly wrong with a few of the following trees: yellow poplars, scarlet oaks, London planes, or American sweetgums. All are fast-growing hardwoods that require little maintenance (and thus little use of gas-guzzling equipment), and have proved to be solid carbon absorbers in tests. According to a 2002 survey of several hundred New York City trees, a yellow poplar (also known as the tulip tree) was the carbon sequestration champion, socking away an impressive 137.26 pounds of carbon. (The runner-up, strangely, was a European beech, at 112.39 pounds.)
The Lantern’s answer might be different a few years hence, thanks to a recent wave of research on hybrid trees. Scientists in Asia and the United States are all working to breed trees that are far better at absorbing carbon than their predecessors; this past October, for example, Japanese researchers announced they’d developed a hybrid larch that fixes 30 percent more carbon than normal larches.
How might planting, say, a half-dozen such supertrees on your property affect your household’s annual carbon footprint? Let’s say that a hybrid yellow poplar can be engineered to sequester 30 percent more carbon than the regular variety, for a grand total of 178.44 pounds per year. Multiply that by six trees, and you’ve offset 1,071 pounds of carbon. That, in turn, translates into 3,931 pounds of carbon dioxide, or 1.78 metric tons. Estimates vary widely, but the average American household’s annual carbon footprint is around 22 metric tons.
Of course, if you have enough property to plant six yellow poplars in the first place, your carbon footprint may be a lot higher than that.
Is there an environmental quandary that’s been keeping you up at night? Send it to email@example.com, and check this space every Tuesday.
Silicon Oxide structure created using selective HF etching, by Yumin Shen, graduate student in Physics at The UO. 436X Magnification
SILVER NANOPARTICLES COATING SILICA SPHERES, BY MOLLY EMMONS, GRADUATE STUDENT IN CHEMISTRY AT THE UO. 7,550X MAGNIFICATION
On his way to class last spring, Jim Hutchison pauses to gaze at a huge hole in the ground. To most passersby on the University of Oregon campus, this rain-filled pit is an eyesore surrounded by a chainlink fence. But to Hutchison, a chemistry professor, it’s the foundation of what will be home to an exciting new field—nanotechnology, the science of the very, very small. When it officially opens in early 2008, the underground Lorry I. Lokey Laboratories (carved deep into the bedrock to isolate delicate instruments from the vibrations of passing vehicles) will establish solidly the University of Oregon as a leading center for this nascent science.
Nanotechnology’s proponents say its promised breakthroughs will change the world: from ultraefficient photovoltaic cells that turn sunlight into electricity to carbon nanowires 100 times stronger than steel; from “quantum dots”—exotic light-emitting crystals used to detect and treat diseases—to wastewater technologies that extract toxic metals from groundwater. Nanotechnology products are already hitting the market.
But some environmental organizations, such as the international Erosion, Technology, and Concentration (ETC) group, claim that nanotechnology “poses enormous environmentaland social risks and must not proceed—even in the laboratory— in the absence of broad societal understanding and assessment.” Such environmental groups warn that these ultrasmall materials might escape into the environment or sneak into the human body with unknown consequences.
Although Hutchison does not share the views of ETC, he is also concerned about the effects of new technologies—and is doing something about it. He is well known in scientific circles for his pioneering work as a “green chemist,” committed to enhancing product safety and promoting sustainable manufacturing practices. Back in his cluttered office in Onyx Bridge, the Luke Skywalkerish–looking Hutchison says he wants materials scientists to learn from chemistry’s past mistakes and make this new science green. “Society has an incredible amount to gain from nanotech,” he says. “If we do it right, almost every area of life will be affected.” But if scientists fail to examine potential risks as well as benefits, says Hutchison, the new science may run into opposition that could thwart its enormous promise.
SYDNEY (Thomson Financial) – China supports APEC moves to tackle climate change but the ‘main channel’ for international agreement on the global problem should be the United Nations, President Hu Jintao said Thursday.
Australian Prime Minister John Howard has made climate change a key item at the Asia-Pacific Economic Cooperation (APEC) summit and hopes to push leaders towards a declaration here which would set goals on energy efficiency.
But the 21 member economies remain sharply divided over the issue and will not accept Australia’s current draft, which urges developing nations to do more to tackle the problem.
Hu said China took the issue of climate change very seriously and was happy it was being brought up here, but said discussions on a solution needed to be led by the United Nations.
He said he hoped a Sydney declaration ‘will give full expression to the position that the UN Framework Convention on Climate Change should remain the main channel for the international effort to tackle climate change.’
‘And it should also give full expression to the principles set in the convention in the problem of the differentiated responsibilities.’
Some developing economies have said they are opposed to binding targets which would hamper their economic development.
Howard would not comment on reports that the 21 APEC economies remained so divided on the issue.
‘I will wait for the meeting to hear the views of the other economies,’ he said.
JERUSALEM (AP) — Archaeologists digging in northern Israel have discovered evidence of a 3,000-year-old beekeeping industry, including remnants of ancient honeycombs, beeswax and what they believe are the oldest intact beehives ever found.
One of the ancient beehives found at Tel Rehov in Israel.
The findings in the ruins of the city of Rehov this summer include 30 intact hives dating to around 900 B.C., archaeologist Amihai Mazar of Jerusalem’s Hebrew University told The Associated Press. He said it offers unique evidence that an advanced honey industry existed in the Holy Land at the time of the Bible.
Beekeeping was widely practiced in the ancient world, where honey was used for medicinal and religious purposes as well as for food, and beeswax was used to make molds for metal and to create surfaces to write on. While bees and beekeeping are depicted in ancient artwork, nothing similar to the Rehov hives has been found before, Mazar said.
The beehives, made of straw and unbaked clay, have a hole at one end to allow the bees in and out and a lid on the other end to allow beekeepers access to the honeycombs inside. They were found in orderly rows, three high, in a room that could have accommodated around 100 hives, Mazar said.
The Bible repeatedly refers to Israel as a “land of milk and honey,” but that’s believed to refer to honey made from dates and figs — there is no mention of honeybee cultivation. But the new find shows that the Holy Land was home to a highly developed beekeeping industry nearly 3,000 years ago.
“You can tell that this was an organized industry, part of an organized economy, in an ultra-organized city,” Mazar said.
At the time the beehives were in use, Mazar believes Rehov had around 2,000 residents, a mix of Israelites, Canaanites and others.
Ezra Marcus, an expert on the ancient Mediterranean world at Haifa University, said Tuesday the finding was a unique glimpse into ancient beekeeping. Marcus was not involved in the Rehov excavation.
“We have seen depictions of beekeeping in texts and ancient art from the Near East, but this is the first time we’ve been able to actually feel and see the industry,” Marcus said.
The finding is especially unique, Marcus said, because of its location in the middle of a thriving city — a strange place for thousands of bees.
This might have been because the city’s ruler wanted the industry under his control, Marcus said, or because the beekeeping industry was linked to residents’ religious practices, as might be indicated by an altar decorated with fertility figurines that archaeologists found alongside the hives.
(CNN) — A virus found in healthy Australian honey bees may be playing a role in the collapse of honey bee colonies across the United States, researchers reported Thursday.
Honey bees walk on a moveable comb hive at the Bee Research Laboratory, in Beltsville, Maryland.
Colony collapse disorder has killed millions of bees — up to 90 percent of colonies in some U.S. beekeeping operations — imperiling the crops largely dependent upon bees for pollination, such as oranges, blueberries, apples and almonds.
The U.S. Department of Agriculture says honey bees are responsible for pollinating $15 billion worth of crops each year in the United States. More than 90 fruits and vegetables worldwide depend on them for pollination.
Signs of colony collapse disorder were first reported in the United States in 2004, the same year American beekeepers started importing bees from Australia.
The disorder is marked by hives left with a queen, a few newly hatched adults and plenty of food, but the worker bees responsible for pollination gone.
The virus identified in the healthy Australian bees is Israeli Acute Paralysis Virus (IAPV) — named that because it was discovered by Hebrew University researchers.
Although worker bees in colony collapse disorder vanish, bees infected with IAPV die close to the hive, after developing shivering wings and paralysis. For some reason, the Australian bees seem to be resistant to IAPV and do not come down with symptoms.
Scientists used genetic analyses of bees collected over the past three years and found that IAPV was present in bees that had come from colony collapse disorder hives 96 percent of the time.
But the study released Thursday on the Science Express Web site, operated by the journal Science, cautioned that collapse disorder is likely caused by several factors.
“This research give us a very good lead to follow, but we do not believe IAPV is acting alone,” said Jeffery S. Pettis of the U.S. Department of Agriculture’s Bee Research Laboratory and a co-author of the study. “Other stressors on the colony are likely involved.”
This could explain why bees in Australia may be resistant to colony collapse.
“There are no cases … in Australia at all,” entomologist Dave Britton of the Australian Museum told the Sydney Morning Herald last month. “It is a Northern Hemisphere phenomenon.”
Bee ecology expert and University of Florida professor Jamie Ellis said earlier this year that genetic weakness bred into bees over time, pathogens spread by parasites and the effects of pesticides and pollutants might be other factors.
Researchers also say varroa mites affect all hives on the U.S. mainland but are not found in Australia.
University of Georgia bee researcher Keith S. Delaplane said Thursday the study offers a warning — and hope.
“One nagging problem has been a general inability to treat or vaccinate bees against viruses of any kind,” said Delaplane, who has been trying to breed bees resistant to the varroa mite.
“But in the case of IAPV, there is evidence that some bees carry genetic resistance to the disorder. This is yet one more argument for beekeepers to use honey bee stocks that are genetically disease- and pest-resistant.”
Bee researchers will now look for stresses that may combine to kill bees.
“The next step is to ascertain whether IAPV, alone or in concert with other factors, can induce CCD [colony collapse disorder] in healthy bees,” said Ian Lipkin, director of the Center for Infection and Immunity at Columbia University Mailman School of Public Health.
Besides the Columbia and USDA researchers, others involved in the study released Thursday include researchers from Pennsylvania State University, the Pennsylvania Department of Agriculture, the University of Arizona and 454 Life Sciences.
by Bijal Trivedi
September 01, 2007 – New Scientist.com news service – TODAY, and every day, you can expect to be exposed to some 75,000 artificial chemicals. All day long you will be breathing them in, absorbing them through your skin and swallowing them in your food. Throughout the night they will seep out of carpets, pillows and curtains, and drift into your lungs. Living in this chemical soup is an inescapable side effect of 21st-century living. The question is: is it doing us any harm?
There are good reasons to think that it might be. Not because of the action of any one chemical but because of the way the effects of different components combine once they are inside the body. As evidence stacks up that this “cocktail effect” is real, regulators around the world are rethinking the way we measure the effects of synthetic mixtures on health.
Environmentalists have long warned of this danger, but until recently there was no solid evidence to confirm their fears – nor any to allay them. Most toxicity testing has been done on a chemical-by-chemical basis, often by exposing rats to a range of concentrations to find the maximum dose that causes no harm. It’s a long way from gauging the effects of the complex mixtures we experience in everyday life, and that could be a dangerous omission.
“When you get a prescription the doctor will ask what else you are taking, because they are concerned about drug interactions, which everyone knows can be quite devastating,” says Shanna Swan, director of the Center for Reproductive Epidemiology at the University of Rochester in New York. This also happens with chemicals like pesticides and endocrine disrupters, she adds. “You have to consider their interactions, and we are just starting to do that.”
To assess the risk posed by such mixtures, a small number of scientists in Europe and the US are now testing chemical brews on yeast, fish and rats. The effects could be additive, or they might be synergistic – that is, greater than the sum of the parts. They could even cancel each other out. Finding out is important, because we don’t have enough data on many compounds to anticipate how they will interact when mixed. Other researchers are probing for associations between disease in humans and past exposure to groups of chemicals.
Andreas Kortenkamp, an environmental toxicologist at the School of Pharmacy, University of London, and his colleagues developed an interest in these mixture effects after they noticed a rise in endocrine disorders, suggesting that the body’s hormonal systems may have been disrupted. In men there were increases in congenital malformations like hypospadia – in which the urethra is on the wrong side of the penis – and cryptorchidism, a condition in which the testes fail to descend into the scrotum. There was also a rise in testicular cancer and lower sperm counts. In women there were more breast cancers and polycystic ovaries.
These increases posed a conundrum for the researchers. When they examined people who had these disorders, and their mothers, they found they had only very low levels of the chemicals that are known to cause the disorders; in the lab, only much higher concentrations of these individual compounds have be found to produce the same effects. This led Kortenkamp to suspect that mixtures were the missing link. He wondered if the effects of different chemicals, acting through the same biochemical pathway, could add up.
Kortenkamp’s group focused on groups of chemicals called xenoestrogens, compounds that disrupt the activity of the hormone oestrogen and induce the development of female sexual characteristics. High levels of xenoestrogens in the environment have been shown to feminise male fish, and have even driven one species in an isolated experimental lake in Canada almost to extinction.
In 2002 Kortenkamp and his colleagues tested a mix of eight xenoestrogens on yeast. These included chemicals used as plasticisers, sunscreen ingredients and others found in cooling and insulating fluids. In the mixture, each was below the level that toxicologists call the “no-observed-effect concentration” – the level that should be safe. Sure enough, the combination triggered unusual effects in the yeast. Kortenkamp and his colleagues dubbed the mixture effect “something from nothing” (see Diagram).
Kortenkamp and his colleagues found that if the doses of all eight chemicals were simply added together, after adjusting for the varying potencies, this new cumulative dose could be used to predict the effect – a principle called “dose addition”. “This result was to be expected, but it had never been shown with endocrine disrupters until our work,” says Kortenkamp. Intuitively this makes sense, he says: “Every mixture component contributes to the effect, no matter how small.”
Since then the effect has been shown with other species, too. Kortenkamp and his colleagues now report that mixtures of xenoestrogens feminised males to varying degrees even though the individual components should have been harmless. In July this year the team showed that a blend of anti-androgens – chemicals that block the effect of male sex hormones – can work in the same way. They exposed pregnant rats to two common fungicides, vinclozolin and procymidone, and the prostate cancer drug flutamide, and then screened the male offspring for reproductive deformities. At higher doses, each of these three chemicals wreaks havoc with sex hormones, and they all do it via the same mechanism: they disrupt male development by blocking androgen receptors and so prevent natural hormones from binding. The researchers found that even when the chemicals were used in doses that had no effect when given individually to pregnant rats, a mixture of them disrupted the sexual development of male fetuses.
Earl Gray, an ecotoxicologist at the reproductive toxicology division of the US Environmental Protection Agency’s Health and Environmental Effects Research Laboratory (HEERL) in Research Triangle, North Carolina, and his team also tried exposing pregnant rats to vinclozolin and procymidone. When they exposed the animals to the compounds individually, they too saw no effect. But when they combined the two, half of the males were born with hypospadia. Gray calls this phenomenon “the new math – zero plus zero equals something”.
Gray then tried the same experiment with phthalates – the ubiquitous compounds that are used to soften plastics and thicken lotions, and are found in everything from shampoo to vinyl flooring and flexible medical tubing. They also disrupt male development, in this case by stopping the fetus from making testosterone. The mix of two phthalates that Gray used caused many of the same effects on male rat fetuses as a mixture of vinclozolin and procymidone.
It makes sense that chemicals targeting the same pathway would have an additive effect. But what about mixtures of chemicals that work via different mechanisms? Surely the individual doses of such chemicals would not be additive in the same way.
“The mixture of different chemicals shouldn’t have had any effect. But it did”
In 2004, Gray and his team put this to the test by mixing procymidone with a phthalate at levels that, on their own, would produce no effect. Because the chemicals work via different routes, he expected that the combination wouldn’t have any effect either. But they did. Then the team mixed seven compounds – with four independent routes of action – each at a level that did not produce an effect. “We expected nothing to happen, but when we give all [the compounds] together, all the animals are malformed,” Gray says. “We disrupted the androgen receptor signalling pathway by several different mechanisms. It seems the tissue can’t tell the difference and is responding in an additive fashion.”
All of this is throwing up problems for regulatory agencies around the world. Governments generally don’t take into account the additive effects of different chemicals, with the exception of dioxins – which accumulate to dangerous levels and disrupt hormones in the body – and some pesticides. For the most part, risk assessments are done one chemical at a time.
Even then, regulation is no simple issue. First you need to know a chemical’s potency, identify which tissues it harms and determine whether a certain population might be exposed to other chemicals that might damage the same tissue. Add in the cocktail effect and it gets harder still. “It is a pretty difficult regulatory scenario,” admits Gray. “At this point the science is easier than implementing the regulatory framework.”
Mixed up inside
For one thing, with many mixtures it’s almost impossible to work out how much we’re getting. The endocrine disrupter diethyl phthalate, for example, easily escapes from plastics and is in so many different products – from toothbrushes to toys, and packaging to cosmetics and drugs – that it would be difficult to work out the aggregate exposure from all sources, says Gray. This also makes it tricky to investigate possible links between chemical mixtures and disease. “Everyone has exposure to chemicals, even people living in the Arctic,” says John Sumpter, an ecotoxicologist at Brunel University in London. “We can’t go to a group with a mixture of nasty chemicals and then go to another who have had no exposure and compare their rate of breast cancer risk or sperm count. We are doing a scientific experiment by letting these chemicals accumulate in our bodies, blood and wildlife.”
That’s why some researchers are suggesting new ways to gauge the effects of chemical mixtures on the body. For example, rather than trying to identify levels of individual xenoestrogens in a patient’s blood, it may be more efficient to take a serum sample and determine the “oestrogenic burden” being imposed on their body from a variety of different sources by testing the sample on oestrogen-sensitive cells in the lab. “It might work well as a screening tool to identify people with potential problems,” says Linda Birnbaum, director of the experimental toxicology division at HEERL. Then, for example, you could make cocktails of foods, water and other products from the person’s life to try to identify the source of the chemicals.
Nicolás Olea, a doctor and oncologist at the University of Granada, Spain, is already trying this kind of approach. He is exploring whether exposure to chemicals with oestrogenic activity leads to genital malformations like cryptorchidism and hypospadia in men, and breast cancer in women. He and his colleagues took samples from various tissues and measured the ability of the environmental contaminants in them to trigger the proliferation of lab-cultured oestrogen-sensitive cells. Because it is difficult to predict from a compound’s structure whether it might have oestrogenic effects, a cell-based assay like this is a cheap way to screen potentially harmful chemicals. They found that the higher this “total effective xenoestrogen burden” the greater the chance the contaminants could disrupt oestrogen-dependent processes.
Others are cautiously optimistic about Olea’s approach. “The concept is correct, I cannot comment on how well the cell effect tracks a cancer effect,” says James Pirkle, deputy director of the US Centers for Disease Control’s Environmental Health Laboratory in Atlanta, Georgia.
Shanna Swan is doing something similar. In a study published in 2005 she showed that boys whose mothers had had higher levels of five phthalates while their babies were in the womb had a shorter distance between the anus and genitals – a marker of feminising activity. They also had higher rates of cryptorchidism compared to sons of mothers with lower phthalate levels. Swan devised a cumulative score to reflect exposure levels to all five phthalates and found that score was “very predictive of ano-genital distance”.
The method is still expensive, and a regular “phthalate scan” isn’t on the cards just yet. A potentially less costly approach, says Pirkle, is regular biomonitoring of subsets of the population to measure the levels of dangerous chemicals in blood and urine, and link particular chemicals to specific health effects. Every two years since 2001, the US Centers for Disease Control has published data on the US population’s exposure to a range of potentially harmful chemicals. In 2005 the agency released data for 148 chemicals; next year it plans to release a report covering 275. While that number falls far short of the number of new chemicals entering the fray each year, Pirkle says that technology is making it ever easier to monitor new substances. The reports do not consider specific mixtures but include exposure data for each individual chemical to make it easier to calculate the likely effects of mixtures.
The European Union, meanwhile, is taking steps to control the number of chemicals being released in the first place. On 1 June its REACH (registration, evaluation, authorisation and restriction of chemical substances) regulations became law. The aim is to cut health risks associated with everyday chemicals by forcing chemical manufacturers and importers to register their compounds and provide safety information to the new European Chemicals Agency, based in Helsinki, Finland. This information must be provided before the chemicals are sold. The new law shifts the burden of responsibility for the health effects of chemicals from government to industry and is also intended to encourage the use of less harmful alternatives for the more toxic chemicals.
Not everyone is so worried about the cocktail effect. Some researchers even find it reassuring – or at least not as bad as it could be. Kevin Crofton, a neurotoxicologist at the EPA, explored how a mixture of 18 polyhalogenated aromatic hydrocarbons found in electrical equipment, flame retardants and paints could disrupt thyroid hormone levels in rats. At the lowest doses of the mixture the effect on the levels of the thyroid T4 hormone was what you would expect from the principle of dose addition; at the highest doses the effect was twice that. “Some people would call that synergy,” says Crofton, “but it is not a very big synergistic effect. It was a twofold difference.”
He adds: “These results are quite reassuring because EPA’s default to calculate the cumulative risk of mixtures is dose addition.” Only recently, however, have scientists like Crofton been able to prove that this default is correct. “If it had been a 20-fold difference I would have said, ‘Boy, the agency needs to look into how it is doing things.'”
Kortenkamp says that regulatory bodies seem to be starting to acknowledge that chemical-by-chemical risk assessment provides a false sense of security. In November last year around 100 scientists and EU policy-makers at the “Weybridge +10” workshop held in Helsinki concluded that mixture effects must be considered during risk assessment and regulation. The European Commission plans to spend more on probing the effects of environmental chemicals on human health.
For now, though, chemicals are an inescapable part of life. And while high-profile campaigns by pressure groups like WWF seek to alert us to what they see as the dangers of artificial chemicals, some toxicologists warn that they may be overstating the case. “I think you need to be careful about hyping the risk,” says Crofton, referring to stories in which individuals have been screened for several hundred chemicals. “When you say I have 145 chemicals in my body, that in itself does not translate into a hazard. You have to know something about the dose, the hazard and how all these chemicals can add up.” Olea, however, suggest that it is sensible to be cautious. “If you don’t know it is good, assume it is bad,” he says.
Like it or not, the chemicals are with us. “People can’t keep phthalates [or other chemicals] out of their air, water or food,” says Swan. “Most people don’t have the information or money to do these things.” A more productive approach might be to tell people how to limit exposure to harmful substances and request better labelling from manufacturers. “We need to put a lot of money into figuring out what these things do in real-world scenarios and take regulatory action,” she says. “Just like we limited cigarette smoke exposure, we’ll have to limit other exposures.”
Bijal Trivedi is a freelance science writer based in Washington DC
From issue 2619 of New Scientist magazine, 01 September 2007, page 44-47
By David Stipp, Fortune
The mysterious disappearance of millions of bees is fueling fears of an agricultural disaster, writes Fortune’s David Stipp.
Pennsylvania apiarist Dennis vanEngelsdorp helped form a group trying to crack the case of the vanishing insects.
A frame removed from a hive afflicted by colony collapse disorder (CCD). The ‘smoker’ on top is used to sedate the bees.
David Hackenberg sounded the alarm about collapsing colonies.
(Fortune Magazine) — It’s a sweet time for honeybees in the rolling hills of eastern Pennsylvania, and the ones humming around Dennis vanEngelsdorp seem too preoccupied by the blooming knapweed nearby to sting him as he carefully lifts the top off their hive. VanEngelsdorp, Pennsylvania’s state apiarist, spots signs of plenty within: honeycomb stocked with yellow pollen, neat rows of wax hexagons housing larval bees, and a fertile queen churning out eggs.
But something has gone terribly wrong in this little utopia in a box. “There should be a lot more workers than there are,” he says. “This colony is in trouble.”
That pattern — worker bees playing Amelia Earhart — has become dismayingly familiar to the nation’s beekeepers over the past year, as well as to growers whose crops are pollinated by honeybees. A third of our food, from apples to zucchinis, begins with floral sex acts abetted by honeybees trucked around the country on 18-wheelers.
The mysterious deaths of the honeybees
We wouldn’t starve if the mysterious disappearance of bees, dubbed colony collapse disorder, or CCD, decimated hives worldwide. For one thing, wheat, corn, and other grains don’t depend on insect pollination.
But in a honeybee-less world, almonds, blueberries, melons, cranberries, peaches, pumpkins, onions, squash, cucumbers, and scores of other fruits and vegetables would become as pricey as sumptuous old wine. Honeybees also pollinate alfalfa used to feed livestock, so meat and milk would get dearer as well. Ditto for farmed catfish, which are fed alfalfa too.
And jars of honey, of course, would become golden heirlooms to pass along to the grandkids. (Used for millennia as a wound dressing, honey contains potent antimicrobial compounds that enable it to last for decades in sealed containers.)
In late June, U.S. Agriculture Secretary Mike Johanns starkly warned that “if left unchecked, CCD has the potential to cause a $15 billion direct loss of crop production and $75 billion in indirect losses.”
$9.3 billion worth of endangered crops
Late last year vanEngelsdorp, a strapping, 37-year-old Netherlands native with a thatch of blond hair and a close-cropped goatee, helped organize a group of bee experts to identify the killer. In recent months he’s acted as the team’s gumshoe, driving thousands of miles to collect bees and honeycomb samples from CCD-afflicted hives to analyze for clues.
Meanwhile, Pennsylvania State University entomologist Diana Cox-Foster has scoured bees from collapsed colonies for signs of disease-causing microbes. She’s shown that the insects are chock-full of them, as if their immune systems are suppressed.
Now the entomologists, aided by Ian Lipkin, a Columbia University scientist known for cracking the case of the West Nile virus (he identified the mosquito-transmitted killer of birds and sometimes people), are closing in on possible culprits and reportedly have submitted a study identifying a virus associated with CCD to a scientific journal. The bug may have been introduced into the U.S. via imported bees or bee-related products, say researchers familiar with the study.
“If I were a betting man,” says Dewey Caron, a University of Delaware entomologist who co-authored a recent report on CCD’s toll, “I’d bet it’s a virus that’s fairly new or one that’s mutated to become more virulent.” Other pathogens, such as fungi, may have combined forces with the virus, he adds.
But merely showing that germs selectively turn up in cases of CCD, he cautions, won’t necessarily nail the culprit, for it will leave a key question unanswered: Are such microbes the main killers, or has something else stomped bees’ immune systems, making them vulnerable to the infections?
After all, the first report on AIDS focused on a strange outbreak of rare fungal pneumonia, “opportunistic” infections whose root cause was later identified as HIV, the human immunodeficiency virus.
A fight about fish farms
Fortunately, a bee apocalypse seems unlikely at this point. Beekeepers have recovered from CCD-like hits in the past — major bee die-offs seem to occur about once a decade. Most beekeepers recently contacted by Fortune say hives generally appear normal of late.
Still, ominous reports of worker-scarce hives like the one vanEngelsdorp recently examined suggest that whatever causes CCD is still in circulation and may well decimate hives again when bees’ floral support system drops away this fall.
If that happens, “it will be a lot worse than the first time, because [commercial beekeepers] have already spent a lot of their money” replacing lost bees, says Richard Adee, head of the country’s largest beekeeping operation, Adee Honey Farms of Bruce, S.D., which, despite its name, is largely a pollination business.
The losses weren’t insured, he adds: Because of all the unpredictable things that can kill bees, from mites to droughts, insurers have long refused to cover them. “We’ll see a lot of guys just hang it up.”
So that’s the thing to worry about: While CCD isn’t likely to obliterate honeybees, it may wipe out enough migratory beekeepers to precipitate a pollination crisis.
They’re already thin on the ground — a rare breed of truck drivers who also happen to be applied entomologists, amateur botanists, skilled nursemaids of cussed old machines, traveling salesmen, and Job-like nurturers of finicky, stinging insects that, when they’re not mysteriously dying off, can suddenly swarm on you like something out of Hitchcock.
Commercial beekeepers make up only about 1% of the 135,000 owners of hives in the U.S., but they manage over 80% of the nation’s 2.4 million honeybee colonies. If the waning number of hives in the U.S. is any indication, commercial beekeeping was already in a long-term decline before CCD struck — in 1960 there were about five million hives, more than twice as many as there are today.
Meanwhile, demand for pollination services is growing, largely because of our love affair with the almond — it’s increasingly seen as a health food, and the FDA acknowledged in 2004 that there are data “suggesting” a daily dose of 1.5 ounces of almonds or other nuts, along with a low-fat diet, may lower the risk of heart disease. By 2012 nearly 90% of the hives now estimated to exist in the U.S. will be needed to pollinate California’s almond groves each spring, according to the Almond Board of California.
10 crops most at risk
Commercial beekeeping has a lot in common with the disappearing family farm. The typical bee rancher is a salt-of-the-earth, 50-something, strong-armed guy who often sweats through the night forklifting hives filled with seriously annoyed bees onto a flatbed semi in order to rush them to his next customer’s field 500 miles away, which just may be near a crop sprayed with insecticides that will kill 15% of his livestock as they wing around the area.
Cheap honey imported from China and Argentina has clobbered his profits, forcing him to work his bees ever harder as migratory pollinators. He loses lots of bees to “vampire” mites, hive-busting bears, human vandals, and sometimes to beekeepers gone bad, who steal hives by night and pollinate by day. His kids can see that there are much easier ways to make a living.
But for all that, he’s never lost the sense of wonder that came over him the first time he heard the piping of a queen — a kind of battle cry that newly emerged honeybee queens make before fighting to the death for hive supremacy. From outside a hive, it sounds like a child wistfully tooting a toy trumpet in a distant room.
If CCD flares up again, one of the casualties may be the Paul Revere of colony collapse, a lanky, 58-year-old beekeeper named David Hackenberg. The story of the disappearing bees began one afternoon last October when he and his son Davey pulled into one of their “bee yards” near Tampa to check on 400 hives they had placed there three weeks earlier.
The Hackenbergs’ main center of operations is a farm near Lewisburg, Pa., but like most migratory beekeepers, they move their bees south each winter for a few months of R&R (rest and reproduction) before the rigors of spring pollination.
Hackenberg, a gregarious raconteur with a Walter Brennan voice, says the first sign of trouble was that “there were hardly any bees flying around the hives. It was kind of a weird sensation, no bees in the air. We got out our smokers” — bellows grafted to tin cans that beekeepers use to waft bee-sedating smoke into hives before opening them – “and smoked a few hives, and suddenly I thought, ‘Wait a minute, what are we smoking?’
“Next thing, I started jerking covers off hives … It was like somebody took a sweeper and swept the bees right out of the boxes. I set there a minute scratching my head, then I literally got down on my hands and knees and started looking for dead bees. But there weren’t any.”
Attack of the mutant rice
Hackenberg spread the word about his vanished bees. Within days other beekeepers began reporting similar cases. Penn State’s Cox-Foster, vanEngelsdorp, and other bee experts launched an investigation. After turning up more than a dozen cases of collapsing colonies across the country, the team issued a report in mid-December telling of beekeepers who’d lost up to 90% of their bees.
The “unprecedented losses,” according to the report, had many keepers “openly wondering if the industry can survive.”
By late spring CCD had made headlines around the world. Assorted phobia purveyors vied to adopt the die-off as a poster child for everything from cellphone emanations to God’s Just Wrath. Internet bloggers thrilled themselves silly bandying about a sentence from Albert Einstein, which the great physicist apparently tossed off about 40 years after his death to the public-relations department of a French beekeeping group: “If the bee disappears from the surface of the earth, man will have no more than four years to live.”
A survey sponsored by Bee Alert Technology, a Missoula, Mont., firm that sells hive-tracking devices and other bee wares, turned up reports of CCD in 35 states and Puerto Rico by early June.
Despite the widespread impression that CCD started with Hackenberg’s losses last October in Florida, says Bee Alert CEO Jerry Bromenshenk, “our survey shows that it probably first began to show up the previous spring in Michigan, Wisconsin, and Iowa. By midsummer [last year] it was moving through the heartland,” hitting hives in the Dakotas, then appearing widely a few months later in the South and on both coasts.
A survey led by vanEngelsdorp and Florida apiary inspector Jerry Hayes suggests that a quarter of U.S. beekeepers were struck by CCD between September 2006 and March 2007. Those hit by mysterious die-offs lost, on average, 45% of their hives.
The surveys failed to show patterns suggesting CCD’s cause. But they provided alibis for some prime suspects, such as beekeeper enemy No. 1: blood-sucking Varroa destructor mites. (Picture a tick as big as a Frisbee glommed onto your back — that’s what Varroa is like for a bee.) Varroa both transmits harmful viruses to bees and suppresses their immune systems.
But CCD has been reported in many hives without significant mite problems, says Jeff Pettis, an entomologist at the U.S. Department of Agriculture’s Bee Research Laboratory in Beltsville, Md.
Sugar cane ethanol’s not-so-sweet future
Another leading suspect — stress on bees due to migratory pollination — hasn’t gotten off the hook so easily. Low honey prices coupled with rising pollination fees for certain crops have prompted migratory beekeepers to put their bees on the road more than ever during the past few years.
Some now truck hives coast to coast, beginning in February with California almonds, then moving on to crops in the East, such as Maine blueberries. That potentially exposes bees to ever more diseases and insecticides. And many of the crops, such as cranberries, don’t provide adequate bee nutrition.
The insects aren’t very good travelers either. When a truck carrying bees gets caught in a summer traffic jam, for instance, hives quickly overheat, despite the fact that the millions of workers inside them furiously fan their wings in an attempt to prevent it, says Wes Card, a beekeeper whose Merrimack Valley Apiaries in Billerica, Mass., pollinates crops from California to Maine.
“Then every minute counts,” he adds, for unless the driver can quickly find a way to pull off the road and hose down the hives with cooling water, desperately hot queens emerge from their inner sanctums and typically wind up venturing into nearby colonies on the truck, where they are perceived as alien invaders and promptly killed. (Ironically, worker bees typically execute a condemned monarch by clustering around her and vibrating their wing muscles to generate heat, fatally raising her temperature — beekeepers call it “balling the queen” because the executioners form a ball of bees.) A hot day can turn a load of hives into a costly mess within minutes.
Stress probably isn’t the main culprit, though. In fact, the biggest commercial beekeepers — those with over 500 hives, most of whom are migratory pollinators — lost a smaller percentage of their hives when hit by CCD last winter than did hobbyist beekeepers, according to the survey co-authored by vanEngelsdorp.
Further, there’s some evidence that CCD may antedate the modern stresses put on bees. Large numbers of honeybees have mysteriously vanished a number of times since the mid-19th century, suggesting that CCD may be just the latest episode in a “cycle of disappearance” caused by a mystery disease that periodically flares up like a deadly worldwide flu epidemic.
Still, entomologists who have personally observed the effects of CCD insist that it is unlike any bee die-off they’ve seen. The University of Delaware’s Caron, one of the bee world’s biggest names, says he was stunned when 11 of 12 hives in the school’s apiary collapsed last winter, apparently because of CCD.
“Never in 40 years had I witnessed the symptoms I was seeing,” he says.
Winning in the wine biz
One of CCD’s strangest symptoms, say bee experts, is a phenomenon that might be called the madness of the nurses. Nurse bees are workers that nurture a hive’s preadult bees, called brood. Workers begin their adult lives as nurses, and only during the final third or so of their six-week lives do they become foragers, venturing outside the hive to collect nectar and pollen.
Researchers have discovered that the young nurses are maintained in a kind of immature, thickheaded state by chemical signals emanating from the queen. Nurses aren’t supposed to leave the hive. They’re not ready to cope with the big outside world, which requires a mature bee’s smarts. Besides, with nurses on leave, the all-important brood would wither.
Yet empty hives struck by CCD are often found with intact brood, which means nurses were on the job shortly before all the bees flew off forever. Beekeepers find this gross dereliction of duty much weirder than the disappearance of foragers, which essentially work themselves to death and often die outside the hive.
Says Hackenberg: “Basically, I’ve never seen bees go off and leave brood. That’s the real kicker.”
To explain the psychotic behavior, some beekeepers, including Hackenberg, point the finger at an increasingly popular class of insecticides called neonicotinoids. The chemicals are widely used by farmers on fruits and vegetables that bees pollinate, as well as on corn and other crops often grown nearby.
Soon after Bayer (Charts), the German drug and chemicals concern, first put the products on the market in the early 1990s, they were implicated in a bee die-off in France, where their use was then sharply restricted. Since 2000, studies by French and Italian researchers have suggested that low, “sublethal” doses of the chemicals — which bees might get from lingering traces of the insecticides in fields — can mess up the insects’ memories and navigational abilities, potentially making them get lost. Bayer has countered with its own studies, which it asserts demonstrate that the products, when properly used, don’t pose significant risks.
Honeybees’ exposure to trace amounts of neonicotinoids can’t be ruled out, says Chris Mullin, a Penn State University entomologist investigating whether pesticides are involved in CCD.
But he and other CCD investigators doubt that neonicotinoids will turn out to be the primary culprits. For one thing, many other chemicals to which bees are exposed are nerve toxins that can make them act strange at low doses. And it’s hard to reconcile the rapid, widespread appearance of CCD last year with the fact that numerous such chemicals have long been widely used.
Could infectious microbes induce the nurses’ insanity?
The great corn gold rush
Maybe. Young workers with a disease caused by “sacbrood” virus tend to start foraging abnormally early in life, when their healthy peers are still nursing. And as if discombobulated in their new roles, they fail to collect pollen.
Although sacbrood virus has been detected in bees from some hives with CCD symptoms, as have a number of other viruses, it doesn’t appear to be closely associated with the disorder. But its ability to warp young bees’ behavior suggests that viruses may well induce nurses to do the unthinkable.
Another explanation may make more sense, though: Perhaps the nurses aren’t really acting crazy when they fly away. Instead, their strange behavior may represent a perfectly natural attempt by doomed workers to protect their sisters from killer microbes.
After all, a hive’s workers represent a famously close-knit sorority, geared by evolution to act strictly in the best interests of their colonies. (Male “drones” don’t work, by the way. They loaf about the hive most of their lives, zip out about noon every day in hopes of mating on the wing with young queens, then immediately die after copulating, presumably happy.) Beekeepers have long known that sick bees generally leave the hive to die, minimizing the risk that they will infect others.
In his seminal 1879 tome The A B C of Bee Culture, Amos Ives Root, an early giant of U.S. beekeeping, marveled that “when a bee is crippled or diseased from any cause, he [sic] crawls away … out of the hive, and rids the community of his presence as speedily as possible. If bees could reason, we would call this a lesson of heroic self-sacrifice for the good of the community.”
Might a fast-spreading, immune-suppressing disease be making nurses so sick that their urge to stay put is overruled by the altruistic impetus to depart?
The organic milk price war
The effort to answer such questions has entered a new phase with the recent linking of specific infectious agents to CCD (the ones whose identities are expected to be disclosed soon in a scientific journal). Now Cox-Foster says she and colleagues are trying to reproduce CCD’s effects on bee colonies by seeding healthy hives with the agents — the biomedical equivalent of getting a killer to confess.
Meanwhile, scattered reports over the summer of hives with abnormally few workers and little stored honey have many bee people worried. A few beekeepers, frazzled by earlier heavy losses and worried that truly ruinous ones are on the way, have already bailed out.
CCD 2 would probably be a lot uglier for growers — and for us fruit and veggie eaters — than version one was. In fact, we got lucky the first time it hit: “A lot of the bees brought to California this year were total junk,” their hives sparsely populated because of CCD and other problems, says Lyle Johnston, a Rocky Ford, Colo., beekeeper who arranges the placement of 50,000 hives owned by other keepers in almond groves each spring. “But we had the most perfect weather during the almond bloom that I can recall. It saved our butts,” by enabling bees to take to the air more often than they usually do.
“We dodged the bullet with fruit, too, this year,” says the University of Delaware’s Caron. “We had weak bees, but the weather was exceptional during the apple, blueberry, and cranberry blooms.”
Unfortunately, Caron and others note, by keeping crop prices low, the good weather may have actually discouraged legislators from funding studies on CCD. To beekeepers’ dismay, the farm bill recently passed by the U.S. House of Representatives, which calls for $286 billion to be spent over the next five years on everything from school snacks to biofuels, earmarked no funds specifically for CCD research.
And the lucky run of weather probably won’t last much longer. Extraordinarily dry weather through spring and early summer in California and the Southeast has stressed bees in those regions, potentially setting up many hives for collapse later in the year.
Despite making some progress, cash-strapped scientists looking into CCD aren’t likely to identify what causes it — and ways to fend it off — before the high-risk season for bee die-offs arrives with the onset of cold weather.
So what to do in light of this new, unsolved, and probably ongoing threat to our food supply? Don’t panic. But do take time to slowly savor your next sweet, spicy slice of cantaloupe, watermelon, apple, peach, or pear.
The pure pleasure of it may get a lot rarer.
by Fred Pearce, New Scientist.com, August 16, 2007, SOME climate tipping points may already have been passed, and others may be closer than we thought, it emerged this week. Runaway loss of Arctic sea ice may now be inevitable. Even more worrying, and very likely, is the collapse of the giant Greenland ice sheet. So said Tim Lenton of the University of East Anglia, UK, speaking on Monday at a meeting on complexity in nature, organised by the British Antarctic Survey in Cambridge.
Lenton warned the meeting that global warming might trigger tipping points that could cause runaway warming or catastrophic sea-level rise. The risks are far greater than suggested in the current IPCC report, he says.
Yet climate modellers are in a quandary. As models get better and forecasts more alarming, their confidence in the detail of their predictions is evaporating.
The IPCC says the Greenland ice sheet will take at least 1000 years to melt. But Lenton’s group – whose members include John Schellnhuber, the chief scientist on climate change at the recent G8 meeting in Germany – says the sheet could break up within 300 years, raising sea levels by 7 metres. This would flood hundreds of millions of people or more out of their homes. “We are close to being committed to a collapse of the Greenland ice sheet,” Lenton says. “But we don’t think we have passed the tipping point yet.” The calculations show the Greenland collapse could be triggered by temperatures 1 °C warmer than today’s, of which 0.7 °C is already “in the pipeline”, held up by time lags in the system.
Lenton’s study has identified eight dangerous tipping points that could be passed this century. Several could have a cascade effect, with each triggering the next, he says.
The tipping points include a collapse of a global ocean circulation system known as the thermohaline circulation. Besides shutting down the Gulf Stream, this could also “switch off” the Asian monsoon and warm the Southern Ocean, perhaps destabilising the West Antarctica ice sheet. This would cause a further 7-metre rise in sea levels. Likewise, warming may cause a near-permanent El Niño in the Pacific, which would hasten a runaway burning of the Amazon rainforest and its disappearance by mid-century.
The existence of potential climate-change tipping points should dramatically alter economists’ assessments of how much climate change we should prevent, said Lenton. The trouble is, the discovery of tipping points has also unmasked growing uncertainty about the reliability of conventional climate models.
At the Cambridge meeting Lenny Smith, a statistician at the London School of Economics, warned about the “naive realism” of current climate modelling. “Our models are being over-interpreted and misinterpreted,” he said. “They are getting better; I don’t want to trash them per se. But as we change our predictions, how do we maintain the credibility of the science?” Over-interpretation of models is already leading to poor financial decision-making, Smith says. “We need to drop the pretence that they are nearly perfect.”
He singled out for criticism the British government’s UK Climate Impacts Programme and Met Office. He accused both of making detailed climate projections for regions of the UK when global climate models disagree strongly about how climate change will affect the British Isles.
Smith is co-author, with Dave Stainforth of the Tyndall Centre for Climate Change Research in Oxford, of a paper published this week on confidence and uncertainty in climate predictions (Philosophical Transactions of the Royal Society A, DOI: 10.1098/rsta.2007.2074). It is one of several papers on the shortfalls of current climate models.
Some authors say modellers should drop single predictions and instead offer probabilities of different climate futures. But Smith and Stainforth say this approach could be “misleading to the users of climate science in wider society”. Borrowing a phrase from former US defence secretary Donald Rumsfeld, Smith told his Cambridge audience that there were “too many unknown unknowns” for such probabilities to be useful.
Policy-makers, he said, “think we know much more than we actually know. We need to be more open about our uncertainties.” Meanwhile, the tipping points loom.