Despite the warnings of evolution and history, much agriculture continues to depend on genetically uniform crops. The widespread planting of a single corn variety contributed to the loss of over a billion dollars worth of corn in 1970, when the U.S. crop was overwhelmed by a fungus. And in the 1980s, dependence upon a single type of grapevine root forced California grape growers to replant approximately two million acres of vines when a new race of the pest insect, grape phylloxera (Daktulosphaira vitifoliae, shown at right) attacked in the 1980s.
Although planting a single, genetically uniform crop might increase
short term yields, evolutionary theory and the lessons of history highlight
an undesirable side effect. Planting
genetically uniform crops increases the risk of losing it all when
environmental variables change: for example, if a new pest is introduced
or rainfall levels drop.