Several key ideas seem missing from “Life on the edge”: 1) the fundamental nature of overpopulation and how it combines with technology to drive mass extinction; 2) the concept of functional extinction, an example being the decimated numbers and diminished range of elephants; and 3) a reasonable extrapolation of human technology. The statement that our species “is likely to stick around for the next 100 million years” is absurd. Russ Agreen
Denton, Md.