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WorthlessWatersBy midcentury, seas’value may be drained

The biological riches of the oceans will bespent within decades if current trends con-tinue. A global analysis of marine ecologypredicts that wild seafood will effectivelydisappear by midcentury.

“People have fished for as long as we’vedwelled on the planet,” says study leaderBoris Worm. “Within our lifetime, it’s goingto be over.”

Worm, a marine biologist at DalhousieUniversity in Halifax, Nova Scotia, and aninternational team of scientists examineddata from dozens of localized studies ofchanges in marine biodiversity. In aggre-gate, the studies offer a panoramic view of

how ecosystems respond to species deple-tion. The researchers also consideredwhether species have recovered in placeswhere people discontinued fishing.

In one data set after another, the re-searchers found that each loss of bio-diversity—for example, the disappearancesof gray whales, dolphins, and salmon fromthe North Sea, or the collapse of cod pop-ulations in Massachusetts Bay—increasedthe likelihood of subsequent losses and cutthe odds of ecological recovery.

Possible countermeasures to fish declinesinclude setting off new areas as marinereserves and altering management of unsus-tainable fisheries and destructive coastalactivities. Marine reserves and fisheries clo-sures increase species diversity by an aver-age of 23 percent, Worm and his team find.

The researchers report their findings inthe Nov. 3 Science.

Projected into the future, the trends sug-gest that by 2048, catches of all marineorganisms will fall to less than 10 percentof their historic highs.

Worm says that he came up with thatestimate by crunching data on his laptopcomputer as he proctored a student exam-ination at his university. He was stunned.Disbelieving his computer, he redid themath by hand and confirmed the result.

“Those students I was overseeing … they’llsee the end of seafood,” says Worm.

The year 2048, he says, offers “a very tan-gible deadline of when we’re going to hitthe bottom of the barrel.”

“My guess is it will happen sooner thanthat,” says Elliott A. Norse, president of

the Marine Conservation Biology Insti-tute in Bellevue, Wash. By relying on sim-ple extrapolation, the new study hasunderestimated the immediacy of thethreat, he says. It doesn’t account forChina’s exploding demand for seafood, forexample, or for the impact of climatechange on oceans.

The new study is still impressive, Norsesays, because it “carefully quantifies andconfirms what a lot of smart people … havebeen saying for a long time.”

The oceans provide valuable “ecosystemservices” other than food, says JaneLubchenco, a marine ecologist at OregonState University in Corvallis. These includerecycling sewage into usable nutrients andfostering marine ecotourism. Moreover,coral reefs, mangroves, and other featuresof healthy oceans and coasts protect peo-ple from tsunamis and hurricanes.

“Loss of species diversity is detrimental to[those] human interests,” Lubchenco says.

Despite the bleak new finding, saysNorse, “there is an uplifting message here:If we exercise restraint … and start treatingour Earth as if our lives depend on it, we’regoing to be OK. It is not 2048 or 2040. Westill have some time.” —B. HARDER

A Swarm ofUmbrellas vs.Global WarmingAstronomer thinks small to save Earth

Some wives ask their husbands to take outthe garbage. Roger Angel’s wife asked himto get rid of global warming.

Prompted by her plea, Angel, an astron-omer and acclaimed telescope-mirror de-signer at the University of Arizona in Tucson,began pursuing a space-based solution.

In the plan he came up with, a trillionminiature spacecraft, each about a gram inmass and carrying a half-meter-diametersunshade, would shield Earth.

This cloud of sun-orbiting flyers, about1.5 million kilometers from Earth andstretching over a distance of about100,000 km, would act as a mostly trans-parent umbrella for the entire planet.

The cloud would reduce by 1.8 percent theamount of sunlight reaching Earth, and thatshading would significantly cut global warm-ing, Angel calculates. He describes his ambi-tious plan, which he says could be deployedin about 25 years at a cost of several trilliondollars, in an upcoming Proceedings of theNational Academy of Sciences.

Previous schemes to reduce the sunlightreaching Earth had required far heaviercraft with larger shades. Such vehicles

CODE ORANGE People will soon extract the final drops of biological value from the oceans.A study predicts that wild seafood will drop off the menu by 2048.

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would have to be built in space from lunarmaterial or asteroids.

In contrast, Angel’s proposed flyers,which include shades made of transparentfilm and riddled with holes, can be builtand assembled on Earth, he asserts.

Rather than requiring rocket fuel, whichcould further contribute to global warm-ing, the flyers would be accelerated intospace by a large magnetic field appliedalong 2,000-m-long tracks. With each suchlaunch sending out 800,000 flyers, theproject would require 20 million launchesover a decade.

The flyers would rely on ion propulsion toreach their destination—a position betweenthe sun and Earth in which the craft wouldtake the same amount of time to orbit thesun as Earth does. They would then main-tain a fixed position relative to Earth andshade it for about 50 years.

The flyers would need to continuouslymodify their trajectories. The pressure ofsunlight on a trio of tiltable solar reflectors,embedded with electronics, would auto-matically redirect each craft, keeping thecloud intact or dispersing it as needed.

Several scientists say that there are less-expensive and easier ways to reduce globalwarming. Aluminized Mylar stretchedacross the ground or white paint coveringlarge areas to reflect visible light from Earth

into space “would be vastly cheaper,” saysastronomer Webster Cash of the Univer-sity of Colorado at Boulder.

“It makes much more economic sense tofind ways to address the climate problemdirectly by reducing the pollution thatcauses it,” says climatologist James Hansen,director of NASA’s Goddard Institute forSpace Studies in New York City.

No word has come yet on what Angel’swife thinks. —R. COWEN

Helping HandsBrief rehab method aidsarm activity after stroke

Stroke survivors who have difficulty usingan arm or a hand experience lasting mobil-ity gains after completing an unusual 2-weekrehabilitation program, a newstudy finds.

Constraint-induced move-ment therapy (CIMT) exer-cises a weakened limb repeti-tively while restraining thebetter-functioning limb witheither a sling or a mitt formuch of the day.

Among patients who hadhad strokes within the previ-ous 3 to 9 months, 2 weeks ofclinician-supervised CIMTproduced more mobility in their stroke-weakened arms over the ensuing year thanstandard rehabilitation approaches did,reports a team led by neuroscientist StevenL. Wolf of Emory University School of Med-icine in Atlanta. Wolf and his coworkerspresent their findings in the Nov. 1 Journalof the American Medical Association.

“CIMT should be considered as a valu-able form of rehabilitation for strokepatients who have lost arm function,” Wolfsays. He estimates that as many as 30 per-cent of stroke survivors can benefit fromthis intervention.

In the United States each year, about566,000 people experience arm or handimpairments due to stroke-related braindamage. For most, these mobility difficul-ties last at least 3 months.

The researchers randomly assigned 222stroke patients, recruited from seven hos-pitals across the country, to receive eitherCIMT or standard care, which ranged fromno treatment to various occupational andphysical therapies.

Over 2 weeks, each CIMT participantwore a mitt on his or her less-affected handfor most waking hours. On each weekday,the person received up to 6 hours of train-ing in using the stroke-impaired hand andarm to perform basic tasks, such as writ-ing and eating.

Wolf ’s team evaluated each patient

immediately after the assigned treatment,and again 4, 8, and 12 months later. Dur-ing those assessments, patients performedtasks designed to measure arm and handdexterity and described how well and howoften they used their impaired limbs in dailyactivities. Of the initial participants, 169 completed 12-month evaluations.

Mobility in the affected arm and handimproved for both groups. However, theCIMT participants displayed substantiallygreater advances immediately after treat-ment than the standard-care group did,the scientists say. Mobility advantages forthe CIMT group over the other participantsincreased steadily during the next year.

Study coauthor Edward Taub of the Uni-versity of Alabama in Birmingham had pre-viously directed brain-imaging studies insmall groups of stroke patients and in mon-keys with experimentally severed armnerves. The findings indicated that CIMT

stimulates brain reorganizationthat fosters arm rehabilitation.In the 1980s, animal rightsactivists succeeded in haltingTaub’s work with monkeys.

The new investigationunderscores the value of theinitial monkey research, saysneurologist John R. Marler ofthe National Institute of Neu-rological Disorders and Strokein Bethesda, Md. Wolf ’s study“shows that it’s possible to har-

ness the remarkable plasticity in the brainto improve the lives of stroke patients,”Marler remarks. —B. BOWER

Dribble QuibbleExperiments find thatnew basketball gets slick

A dispute in professional basketball abouta new ball has bounced its way into a physicslab. A study launched last month at the Uni-versity of Texas at Arlington compares a con-troversial plastic ball introduced in presea-son games this summer by the NationalBasketball Association (NBA) with the pre-vious standard—a leather-covered ball. Theofficial basketball season, the first in whichthe new ball will be used, began this week.

So far, the Texas experiments indicatethat the new ball bounces less elastically,veers more when it bounces, and becomesmore slippery when damp than does theofficial leather ball of the past 35 years.

Many NBA players have griped about thenew ball since teams began using it.

“The most significant finding is theslickness of the ball,” says University ofTexas physicist James L. Horwitz. He,physicist Kaushik De, and their colleaguesgauged friction for both new and old balls

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COOLING CONCEPT Miniature flyers madeof transparent film would deflect sunlightfrom Earth. Three solar-reflecting tabs oneach flyer direct its course. This illustrationshows background starlight blurred intodoughnuts by the film.

566,000Yearly numberof U.S. strokepatients wholose arm orhand mobility

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