Venture out into the desert in the spring of an average year, or after the start of the summer rains, and the signs of new life are everywhere. Carpets of roadside green (unfortunately, turning out to be young tumbleweeds by the thousands), choruses of toads, young grasshoppers munching happily away, exuberant new life!
Yet, return a year later, and little has changed. The desert reveals what could be the same patches of tumbleweeds, the same choruses of toads, even the same grasshoppers. With that bountiful crop of newly sprouted and hatched organisms a year ago, why isn't the whole countryside now overrun with tumbleweeds, toads, and grasshoppers? Welcome to the harsh reality of nature! Most of those fresh, new tumbleweeds, toads, and grasshoppers never made it to adulthood, taken by drought, predators, accident, and disease.
Only by the production of what seems to be excessive numbers of
offspring do animals and plants manage to just replace themselves—if they're lucky.
Those that fall even slightly short year after year are on the road to
extinction.
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.
Strickberger, M. W. 2000. Evolution. 3rd ed, Jones and Bartlett, Publishers, Sudbury, MA. 722 pp.