We learned in school that ultimately we are reliant on the sun for our food—that plants use light energy to manufacture food by photosynthesis from carbon dioxide and water. And, of course, that animals get their food by eating plants or eating animals that eat plants. For some of us, the story stops there, but to understand the impact of ourselves and other animals on the biological system, we need to look further.
The ugly truth is that a pound of plant matter isn't equal to a
pound of animal matter. An herbivore needs roughly 10 pounds of plant-derived energy to
build 1 pound of animal body. At every conversion, as when we eat an herbivore such as
a cow, another factor of about 10 comes into play. Thus 1 pound of you equals 10 pounds
of steak and 100 pounds of grass. Very, very rough figures, but indicative of the
comparative impact that our hamburger society has compared to people dependent largely
on plant products. And, of course, we continue eating long after reaching adult
size.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.