Letters from the March 31, 2007, issue of Science News

On the hoof

Do cows and other domestic-herd animals really emit more methane than bison and other wild-herd animals emitted before people came along? Do grass, alfalfa, and other pasture plants remove less carbon dioxide than do forests? There were open grasslands before pastures replaced some forests. I hope the people who are researching these things (“Big footprints,” SN: 1/13/07, p.