TUESDAY, DECEMBER 21, 2010 SCIENCE NEWS


KLMNO THEGREENLANTERN All dead cows are not created equal BY BRIAN PALMER Grass-fed beef is all the rage


these days. Everyone says it tastes better and the technique is more humane for the cattle. But what about the environ- ment? IspasturingEarth-friend- ly or just cow-friendly? Nomatter howyou slice it, eat-


ALAMY


Soot, which comes from diesel engines and the burning of biomass, accounts for 1.5 million deaths per year globally.


Clean-air rules on diesel trucks may be helping California keep its cool Newdatashowthat twodecadesofair-pollutionregulationsin


California for trucks running on diesel fuel have cut levels of black carbon, themain component of soot, in half. Andmodels suggest that the soot reduction may also have cut into the warming of the state’s climate inanunexpectedly bigway. Soot comes mainly from diesel engines and the burning of


wood, charcoal or other biomass. In recent years, scientists have learned that black carbon,which traps both direct sunlight and heat reflected from the ground, has powerful warming effects: Methane, ozone in the lower atmosphere and particulate black carbontogetherwarmtheplanetasmuchas carbondioxide.And asmuchashalfof thelossof snowandiceintheArcticmaybedue to black carbon. Breathing black carbon also harms people’s health: The


United Nations blames soot on 1.5 million deaths per year globally. Research published in the journalAtmospheric Environment


by atmospheric scientist V. Ramanathan of the Scripps Institu- tionofOceanography andcolleagues analyzedhowblackcarbon levels in California fluctuated from 1988 to 2008. During that period, laws requiring cleaner-burning fuels and catalytic con- vertersledtodieselenginesthatpollutedless.Blackcarbonlevels were slashed in half even though diesel fuel consumption in the state rose steadily. More unexpected is the effect on the climate. Globally, green-


house gases produce warming by trapping two to four watts of power from heat given off by the planet per square meter of Earth’s surface.Ramanathan’s groupcalculatedthat,onaverage, the removalof theblackcarbonpreventedanestimated1.4watts per squaremeter of heating, which they say presumably would have added to greenhouse-gas warming in California. Ramana- than called that amount “surprising” and said that it shows how powerful a tool controls onblack carboncouldbe. Controllingdieselemissionsandmakingcleaner-burningcook


stoves,hesays,couldhelplimitwarmingof theplanet if scaledup. Becauseblackcarbonsettlesoutof theatmosphereinafewweeks, instead of the centuries for which carbon dioxide persists in the air, cutting soot emissions could quickly put the brakes on warmingwhilenations revupefforts to cutCO2


emissions. —EliKintisch


This articlewas produced by ScienceNOW, the daily online news service of the journal Science, and can be read online atwww.sciencemag.com.


ing beefwillnever be the greenest thing you do in a day. Scientists at Japan’sNational Institute of Live- stock and Grassland Science esti- mate that producing a kilogram (about 2.2 pounds) of beef emits moregreenhousegas thandriving 155miles.SincetheaverageAmer- ican covers 32 miles to and from work, your eight-ounce steak at dinnermight contribute to global warming as much as your daily commute. Wouldn’t itbenice if carnivores


could minimize their environ- mental impact just by switching from one dead-cow product to another? Unfortunately, both grass-fed and corn-fed beef are bad for theEarth—but each inits ownway. First, a little background on


how a calf becomes a meal. Whether destined for the high- dollar, natural-market butcher or for the convenient-mart freezer case, beef cattle must drink milk and eat grass during their youth. It’s the laterperiodthat cattlemen call “finishing” — the final two months to one year before slaugh- ter — when their diets might di- verge. UnderUSDAregulations, cattle


bearing the “grass-fed” label can eat only foods known as forage once they have beenweaned. For- age includes grass, hay, brassicas (a group of plants that includes turnips,kaleandcabbage)andthe leaves and tender stems of young trees and shrubs. The cattlemust have access to pasture.Unless the beef is labeled organic, they may receive antibiotics andhormones. As Michael Pollan has de-


SUBHANKAR BANERJEE/ASSOCIATED PRESS


Scientists have been warning that the melting of sea ice where polar bears hunt was jeopardizing their existence.


Polar bears can be saved, report says, if carbon dioxide levels are stabilized Significant cuts in projected greenhouse-gas emissions over


thenext twodecades couldgivepolarbears a chanceof surviving over the long termby preserving theArctic sea ice onwhichthey depend, according to a study published online last week in the journalNature. Scientistshavebeenwarningfor sometimethat themeltingof


sea icewhere polar bears huntwas jeopardizing their existence. In2007 a groupof federal scientists ledby StevenC.Amstrup, an emeritus researcher with the U.S. Geological Survey, projected that if greenhouse gas emissions continued to rise as projected, only one-third of theworld’s 22,000 polar bearsmight be left by 2050, andall of themcouldbe gone by the endof the century. Amstrup,who is the lead author of theNature article, said the


analysis he and six other U.S. researchers have just completed suggests that ifpolicymakers cancurbgreenhousegas emissions enough to stabilize atmospheric concentrations of carbon diox- ideatorbelow450partspermillion, enoughArctic ice is likely to remain during the late summer and early autumn to allowpolar bears to survive.Current carbondioxide concentrations arenow at roughly 390partspermillion. “Conserving polar bears appears to be largely a matter of


curbing temperature rise,”Amstrupsaid. “We alsodo realize this will take some considerable effort todo so.” Tomeet the target these scientists have identified, industrial-


izedanddevelopingnationswillhave to increase their reduction targets by asmuchas 50percent inthe comingdecades. Still,Amstrupsaid,hewantedthepublictoknowthat the2007


USGS projections were based on a “business as usual” scenario thatdidnot incorporate steepemissions cuts. “If people and leaders think there’s nothing to do, theywill do


nothing,” saidAmstrup,whonowservesasasenior scientistwith theMontana-basedconservationgroupPolarBears Internation- al. “We have now shown there is something that can be done to savepolar bears.Thisproblemisnot irreversible.”


—JulietEilperin SCIENCE SCAN CAREERCHOICES Next step for Redskins cheerleader


SCIENCECHEERLEADER.COM Give me an S-C-I-E-N-C-E! ScienceCheerleader.com is a blog


about professional cheerleaders who are pursuing careers in science, technology, engineering and math. The founder of the blog is Darlene Cavalier, a former Philadelphia 76ers cheerlead- er who worked at Discover magazine for 10 years and advocates for citizen science, encouraging people to learn about and participate in science through recreational activities and formal research. One of the blog’s top 10 posts of 2010 featured Rachel, a former Redskins cheerleaderwhoenlisted in theNavy and is studying to become an anesthetist. She tried to keep her previous life under wraps, but her Navy co-workers let it slip and it proved to be “a great morale booster in the end” for her patients. They loved talking football with her and finding out what it was like to be an NFL cheerleader.


—Rachel Saslow


scribed over and over and (over) again, the feedlot life differs enor- mously from the idyllic, sun- drenched wonderland of the pas- ture.Whenconventional cows are ready for fattening, they typically moveintoapenwith10to14other animals. Each cow, measuring around five feet long and two feet wide, gets a 16-by-16-foot space, onaverage.Afterabrief transition period, the rancher begins to in- troduce grain into the cow’s diet. While corn-finished cattle don’t only eat corn — they might also consume straw, alfalfa, soy and fruit — the grain can make up as muchas90percentof theirdiet.A feed truck dumps their rations in a trough three times daily, with a side of hormones and antibiotics. From an environmental per-


spective, concentrated animal- feeding operations — CAFOs, as they’re known in the industry —


The Green Lantern is a weekly environmental column from Slate. Read previous columns at www.slate.com/greenlantern.


aren’t great.Putting 1,000pounds of weight on an animal in a few months requires a staggering amountofgrain.Duringits finish- ing period, the average beef cow eats 2,800 pounds of corn. In fact, more of our grain crop goes to feeding animals than humans, and it requires lots of energy to growand transport that feed. Nevertheless, someresearchers


argue that cattle fattened at a CAFOarebetter for theEarththan their free-ranging cousins. JudeCapper, a professor of ani-


mal science at Washington State University, recently compared the energy input for the two kinds of beef. She concluded that grass- finished cattle require about 21/2 times asmuch energy to produce as grass-fed ones. A couple of big caveats: Capper co-authored the paperwithanemployeeofElanco, a company that supplies food and medicinetoCAFOs.Thepaperhas not been published in a peer-re- viewed journal butwas presented at an annual meeting of animal- science associations, of which


MICHAEL SLOAN FOR THE WASHINGTON POST


EZ EE


Science


E3


Elanco happened to be a “plati- numsponsor.” By Capper’s estimation, cows


that live shoulder to shoulder are just like humans crammed into urban spaces: Transporting food to the animals, and the animals to the slaughterhouse, requires less energy. In addition, cows that are hopped up on hormones and eat- ing calorie-dense grain grow two to three times faster, enabling ranchers to crank out more beef with fewer resources. And while finishing a 1,200-pound corn-fed cow requires three acres of land, finishing a grass-fed cowrequires nine acres. Not everyone buys these num-


bers.RancherswiththeAmerican Grassfed Association insist that they use no synthetic fertilizers, contrarytoCapper’sassumptions. There are a host of other farmers claiming their operations are car- bon-negative, and the USDA has gotten behind them. Still, with so little rigorous researchpublished, it’s hard to tellwhich side is right. The numbers depend on a range of variables — such as how much fertilizer a rancher uses to grow grass — for which data simply aren’t available. There’s also a disagreement on


methane, the powerful green- house gas that cows belch (and, to a lesser extent, excrete). Capper believes that a corn diet and a shorter life spanresults inaCAFO cow’s having one-third the meth- ane output of a grass-fed cow. Other researchers, however, have


HOW & WHY how from E1


volves two skills thatmachines are bad at: perceiving their environment and usefully incorporating past experiences into their knowledge base. Think, for aminute, about


what it takes to recognize a canof soda sitting inyour refrigerator. The photons bouncing off the scene inyour refrigerator are recorded onyour retina.The opticnerve translates the image into electrical signals and carries themto your brain. So far, so good for themachines.Digital cameras have long beenable to capture photons and store themas transmittable electrical signals. Thenext step, though, is a


bridge too far formost robots. Your brainmanages to pick out the canfromthe rest of the scene, eventhoughevery time you see a soda can, it looks a little bit different.Your brainhaswhat researchers call aninternal representationof a soda can, so evenif the lighting is different or the background changes or the canis a slightly different size, you still recognize it. It takes an incredible amount of computing power, plus the ability to filter out extraneous details, tomake this happen. Computers are slowly


acquiring the skill.Google, for example, isworking onan “omnivorous searchbox” that can recognize images and sounds recorded ona smartphone.But the technology remains inits infancy. Building a knowledge base is


evenmore difficult for amachine. JohnLaird, a professor of computer science and engineeringwho studies artificial intelligence at theUniversity of Michigan, analogizes computers to themaincharacter inthe 2000 film“Memento,”who cannot makememories ashe tries to


make nifty chess moves


Intelligent robots must do more than


learnexactlywhat ithad to do withinthe course until five minutes before the greenflag. DARPAalso clogged the course upwith30human-drivenFord Tauruses. Six of the 11 teamsmanaged to


complete theirmissions, althougha fewhadminor scrapes. Inspired by thatAI feat, Googlehas entered into a collaborationwithSebastian Thurnof Stanford,whowona previousDARPAchallenge and came insecond inthis one, to develop robotic cars. While robots areworking in


OLIVER BURSTON FOR THE WASHINGTON POST


figure outwhomurderedhiswife. “MostAI systems,” saysLaird,


“donothave episodicmemories. They don’tmake continuous records of their pasts.”Like the lead character in“Memento,” they arewhatLaird calls “cognitive cripples.”While they canstore information, they can’t learnthe way ahumandoes. Evenifwe could construct


computerswithenoughmemory to store decades’worthof conversations,novels,meals and lectures,no onehas figured out howto teachamachine to catalogue and access those memories quickly. For anexample ofhowdata


management is every bit as important as rawcomputing power, considerDeepBlue, the computer that in1997 defeated grandmasterGarryKasparov. Intheory, a computerwith


enoughcomputing capacity should be able to beat ahumanin


chess. It could play out every possible sequence ofmoves and alwaysmake the best choice.But no computer cando those computations fast enough.Deep Blue saved time andRAMby making decisions aboutwhich moveswereworthconsidering andwhichcould be ignored. In otherwords,DeepBlue used a formof reason, andnot just superior processing speed, to beat Kasparov. The field boasts other recent


accomplishments.ThePentagon’s DefenseAdvancedResearch ProjectsAgency, orDARPA, offered a$2millionprize in2007 for a robotically drivencar that couldmerge, park and pass in traffic aswell as ahumandriver could. (Or,hopefully, better, given theway some people drive onthe Beltway.)While the teams competing for the prizewere giventhemap of the urbancourse inadvance, their robots didn’t


Iraq andAfghanistan,most of themare remotely operated by humans.TheDepartment of Defense isworkingwithLaird on a robot that canenter ahouse before soldiers ormonitor a perimeterwhilehumans are inside.Humanswill trainthe robots ahead of time bywalking themthroughmodel buildings. The robotwill projectwhat it sees onto a tablet computer, and trainers canpoint to objects on the screenand give the robot such simple commands as “open.”On the battlefield, soldierswould be able to turnthe robot loose and let itwork. Of course,Laird’s proposed


robots are a far cry fromJames Cameron’sTerminator, and Thrun’swinning robo-vehicle is a longway fromKit of “Knight Rider” fame. It’s going to be decades before a robot passes the Turing test.Engineers suchas VictorZue ofMITareworking on startlingly lifelike digitalhuman images thatwill tell people that their flight is delayed.But there’s nothing of general applicability out there. So don’t expect to be employing your ownrobotic housemaid anytime soon. health-science@washpost.com


Palmer, a freelancewriter based in NewYork, alsowrites for Slate.com.


suggested that grass’s ability to sequester carbon may compen- sate for the difference. Even if Capper is correct on all


counts, it isn’t a TKO for the CA- FOs.There’smore to environmen- talismthangreenhousegases.CA- FOs produce 300 million tons of manureperyear, twicethevolume of human feces. Even if it were spread out, that would be a lot of bull-you-know-what. But it’s par- ticularly bad when concentrated on small patches of land. CAFOs usually capture their waste in la- goonsbeforesprayingitbackonto the fields as fertilizer, but these storage units sometimes fail and can leak into nearby water sourc- es. Large volumes of manure can kill aquatic plant life, the base of the marine food chain. Massive dead zones fromCAFO runoff ex- ist in the Gulf of Mexico and the Chesapeake Bay. Based on some estimates,we spendmore than$4 billionannually trying to cleanup CAFOmanure runoff. Inaddition, the long-term, low-dose antibiot- ics that CAFOs give livestock can lead to antibiotic-resistant bacte- ria, further undermining our sup- ply of usefulmedicines. May the Lantern make a hum-


ble suggestion? Stop eating so much beef. Whether grass- or corn-fed, it’s pretty bad for the environment, and it’s not that great for your body, either.


Is there an environmental quandary that’s been keeping you up at night? Send it to ask.the.lantern@gmail.com.


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