Letters

Turn on the bubble machine

Regarding "Besieged tadpoles send chemical alert" (SN: 6/12/99, p. 375), how can two chambers separated by a screen that allows water to pass freely be acoustically separated? Since water conducts sound about 4 times better than air, I presume the tadpoles could hear each other quite well. Even something as subtle as a slightly elevated heart rate could be enough to alarm other members of a group. Ammonium in the water might be a byproduct of a fear reaction. Many species, including humans, will eliminate waste in extreme situations.

Charles McAlexander
New York, N.Y.

Study author Joseph Kiesecker says that during the trials, all tanks had active airstones that would have made it highly unlikely that any sound produced by the tadpoles could have exceeded the background level. "Our conclusion that the signal is chemical in nature is further supported by the results of experiment two and experiment three," he adds. "Experiment two clearly shows that tadpoles release ammonium when disturbed, and experiment three shows that receiver tadpoles respond to ammonium with antipredator behavior." —S. Carpenter

Give germs their due

The article "Lead and bad diet give a kick in the teeth" (SN: 6/26/99, p. 405) doesn't acknowledge the real pathology at the root of dental caries, a bacterial disease. Streptococcus mutans species have been shown to be the commonest etiologic agents of caries. The article implies that lead alone could be the cause of decay. The study really focuses on a way to modify the host response to resist the pathological process, which will occur despite the elimination of lead's effect.

Thomas W. Ruprecht
Marquette, Mich.

Gas pains

I was disgusted by the thumbs-up attitude in "Good-bye to a greenhouse gas" (SN: 6/19/99, p. 392). Haven't we learned by now that these quick fixes usually come back to haunt us? What a change it would be if we put $29 million toward solutions that have a chance of working: reforestation, mass transit systems, reduced dependency on fossil-fuel industries. The only thing this project will preserve is the status quo for industries at the expense of the taxpayers. As usual, the environment will be the ultimate loser.

Kristina Van Wert
Arcata, Calif.

The article provides the politically correct impression that global warming is a threat and that every effort must be made to prevent it. Please inform your readers that all geological, historical, and scientific evidence to date strongly supports the premise that a warmer climate is much more favorable to humankind than a colder climate.

Charles R. Hosler
Fearrington Village, N.C.

While we must commend efforts to deal with the symptom of increasing carbon-dioxide levels in the atmosphere, we cannot let the cause remain neglected. As we approach Y2K, we also approach Y6B (the year the population reaches 6 billion). In the long run, we will have to achieve a stable population that is compatible with a high quality of life for humans and that does not wreak havoc with global ecosystems.

Diane W. Young
Opelika, Ala.

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