There's good news on the agricultural front: Plants grown as food crops on small farms show a surprising amount of biodiversity worldwide, an international team has found. The findings bode well for efforts to preserve diversity as a hedge against plant diseases, insect pests, and global climate change.
Biodiversity is the great bulwark against crop loss. If a certain kind of plant becomes vulnerable to a particular disease, plant breeders can work with related varieties to develop a hardier strain. The more varieties there are to choose from, the greater the chances scientists have of strengthening a crop's defenses. But as family farms are replaced by large agricultural businesses, which cultivate less diverse crops, scientists have become concerned that the trend endangers agricultural biodiversity.
To gauge the importance of family farms, botanist Devra Jarvis of Bioversity International in Rome and colleagues examined 27 agricultural crops on more than 2000 small farms on five continents. In all, the study took nearly 10 years and covered 63,600 hectares. To the team's surprise, every farmer grew more than one crop variety, and in some cases, such as rice farms in Vietnam and cassava farms in Peru, they grew more than 60 varieties side by side. "There still is a lot of diversity left in farmers' fields," says Jarvis, whose team reports its findings online this week in the Proceedings of the National Academy of Sciences.
The research is important because it presents "the overall message that [small] farms of the world continue to maintain a considerable crop genetic diversity," says plant geneticist Jean-Louis Pham of the Institute of Research for Development in Montpellier, France. The paper's relatively simple data required painstaking efforts to obtain, he says, and no doubt the results will be widely used as a reference, "providing us with a kind of state of the world of crop diversity at the beginning of the 21st century."