SCIENCE

Harry Potter's Protection Spell

It's not wizardry, but Harry Potter apparently protects his legions of youthful fans from injuries, at least during the weekends his newest books keep them huddled indoors on reading marathons, British researchers said.

Stephen Gwilym of the John Radcliffe Hospital in Oxford and his colleagues counted how many 7-to-15-year-old children came to the emergency department on the weekends when J.K. Rowling's two most recent tomes were released and compared them with other summer weekends from 2003 to 2005.

The number of children brought in with injuries during the weekends "The Order of the Phoenix" and "The Half-Blood Prince" were released was about half the usual -- lower than any other weekend in the three-year period, the researchers found. There was nothing else unusual about those weekends, such as odd weather, that could explain the findings, they added.

"Harry Potter books seem to protect children from traumatic injuries," the researchers wrote in the British Medical Journal.

"It may therefore be hypothesized that there is a place for a committee of safety-conscious writers who could produce high quality books for the purpose of injury prevention," they wrote, noting, however, that "potential problems with this project would include an unpredictable increase in childhood obesity, rickets, and loss of cardiovascular fitness."

-- Rob Stein

Problems With Planting Forests

Many policymakers have embraced planting forests as one way to combat the buildup of carbon dioxide in the atmosphere, but a new study suggests this may be a poor strategy for minimizing greenhouse gases because fast-growing trees such as evergreens take a high toll on water and soil resources.

The international team of researchers, who examined more than two dozen plantations in Brazil, Belgium, South Africa, the United States and elsewhere, concluded that planting forests sometimes harmed local streams and damaged the soil. Thirteen percent of the streams they examined dried up completely for at least one year after plantations, many of which featured evergreens, had grown five to 10 years in the area.

"Trees use more water than just about anything else -- grasslands, croplands, shrub lands," said Robert B. Johnson, a Duke University biology professor at the Nicholas School of the Environment, one of the authors of the paper in Friday's issue of journal Science.

The trees they studied -- especially pine and eucalyptus -- also changed the acidity and salinity of the soil by soaking up calcium, nitrogen and potassium while releasing sodium, Johnson said in an interview last week.

The findings raise questions about the wisdom of planting trees to soak up carbon dioxide emissions from cars, power plants and other industrial sources, he said: "It's not a single good-bad story. We have policies that focus strictly on carbon. That's something we should reconsider, the other effects on the environment that putting on these carbon binders have."

-- Juliet Eilperin

A 'Mirror' in Elephant Mating

Mirrors have always played a role in romance. The primping and preening. The practiced puckers. Now science has found a link between mirror images and lust -- or, more precisely, between mirror images and "musth," the state of sexual arousal in animals.

New research shows that a chemical secreted from a gland in aroused male Asian elephants comes in two mirror-image forms. A few atoms poke out in one direction in one form and in the opposite direction in the other form, like two hands with opposing thumbs. One form tells females that the male secreting it is young, of low status and perhaps not worth dating, the research shows, while the other form signifies high social rank and sexual appeal.

The chemical, known as frontalin, is an odor molecule first isolated from a beetle that uses it to signal others at a distance. In recent years male Asian elephants have been found to exude the stuff, too, suggesting it may play a colognelike role in males looking for mates.

In the new work, led by L. Elizabeth L. Rasmussen of Oregon Health & Sciences University in Portland, scientists tested the response of male and female elephants to whiffs of frontalin's two mirror image forms, or enantiomers, that had been swabbed from forehead glands of male elephants.

The form secreted by young males left females cold. But secretions from older males, which consist of an approximately 50-50 mix of the two enantiomers, proved highly attractive to females in the fertile phase of their reproductive cycle. That blend repulsed females who were not in heat, however.

The work indicates that even some of the biggest animals can detect subtle differences in the molecular configurations of tiny airborne molecules, the team reported in the Dec. 22 issue of Nature.

-- Rick Weiss