National Geographic : 1991 Apr
the International Maize and Wheat Improve ment Center in El Batan, Mexico, who has introduced improved, high-yield seeds from India to Egypt. "Problem is," he adds, "the old varieties are disappearing as farmers take up modern ones." Modern farmers prefer the modern variet ies, the plants redesigned by genetic scientists who borrow the best attributes from various seeds and blend them into new ones to increase productivity, to meet the taste of consumers, and to provide maximum protein, among other reasons. But there is a trade-off. By relying on a few crop strains instead of many, farmers open themselves to disaster. In the U. S., for in stance, billions of rows of essentially identical corn are planted each year, making the entire crop vulnerable to a single pest or disease. United States farmers learned that the hard way in 1970, when an unexpected epidemic of corn leaf blight wounded the pride of the world's most agriculturally advanced nation. A virulent new strain of fungus appeared in south Florida that win ter and raced north like a killer flu. Since each ear of corn was a copy of every other, there was no margin of safety. The fungus destroyed half the crop from Florida to Texas. Nationwide losses amounted to 15 percent, at a cost of per haps one billion dollars. Such disasters are nothing new. Through out history the sowing of uniform crops has led to A SCIENTISTON A U. S.- SO VIET PLANT EXPEDITIONCOLLECTS a harvest of tragedy. A SIBERIANFORAGEGRASS, o CHAMPSA CAEPTOSA. The collapse of Clas sic Maya civilization around A.D. 900, some anthropologists specu late, resulted from farmers' planting a mere handful of maize varieties, which were destroyed by a virus. Ireland's infamous potato famine of 1845 started with a fungus accidentally introduced from Mexico. That scourge, spreading through millions of geneti cally similar spuds, left the Irish without their main food source, and nearly a million people starved to death. A few decades later a fungus wiped out the homogeneous coffee plantations SWEET POTATO Tomato Bean Squash La Molina, Pen POTATO SOUTHAMERICA Clearing of rain forest, a e..... nt oftraditional crop vi andpoliticalconflictendai SouthAmerica's genetic re MAJOR FOOD CROPS Today's top 12 crops, in total annualproduction by weight, areshown incapital letters. ® Areas of documented ancestral wild species SLikely reservoirs of wild relatives The race against genetic erosion "Thediversity of our genetic resources stands between us and starvation on a scale we can not imagine," warns leading plant geneticist Jack Harlan. Preventing such catastrophe requires tracking down the wild relatives of modern crops in habitats thought to favor their survival (green on map)-then preserving theirgerm plasm in a worldwide network of gene banks and protected naturalsettings. As population growth continues to degrade the environment, preserving the world's biological diversity is crucial to futurefood production.