Letters from the August 6, 2005, issue of Science News

Empty threat?

“Empty Nets: Fisheries may be crippling themselves by targeting the big ones” (SN: 6/4/05, p. 360) reads as if there is something to be alarmed about. By selectively catching large fish, we have reduced “the mean size [of food fish to] one-fifth of what it was.” This is not cause for alarm. It is cause for a decision: What do we want, small fish or large fish? Humans are the only creatures on the planet who care about fish size, and the only ones empowered to change it.

Peter Wilson
Simi Valley, Calif.

What wavelengths?

The article “Icy Heat: Satellites look at heat flow through Antarctica’s crust” (SN: 6/11/05, p. 373) refers to the Earth’s magnetic field only at very long wavelengths. In over 70 years’ exposure to science, I have never heard of our magnetic field having wavelengths. Please elaborate.

Kenneth E. Stone
Cherryvale, Kan.

Looking at Earth’s magnetic field at long wavelengths is analogous to looking at a picture in low resolution, says Cathrine Fox Maule of the Center for Planetary Science in Copenhagen. Small variations in the field due to local anomalies in the crust disappear, leaving only regional variations, which scientists can interpret as differences in heat flow through the crust.—S. Perkins

Fungus fallacy

“Farmers without Fungus: How to store peanuts to reduce toxins” (SN: 6/11/05, p. 374) made the minimization of aflatoxins in peanuts sound beneficial until the recommendation to treat the ground beneath the peanut pallets with insecticides. This will induce harm to the soil wildlife on which African farmers and villagers are dependent and to any nearby water sources. It will also add a toxic substance to the peanuts.

Darlene Schanfald
Sequim, Wash.