from the Environment News Service: http://ens-news.com/ Industrial Farming Causes Trouble for Bees PRINCETON, New Jersey, December 20, 2002 (ENS) - Intensive, industrial scale farming may be damaging one of the very natural resources that successful crops require: pollinating bees. A study by scientists at Princeton University found that native bee populations plummet as agricultural intensity goes up. In farms studied in and around the Sacramento Valley in California, concentrated farming appeared to reduce bee populations by eliminating natural habitats and poisoning them with pesticides, the researchers reported. U.S. farmers may not have noticed this effect because they achieve much of their harvests with the help of imported bees rented from beekeepers. These rented bees, however, are in decline because of disease and heavy pesticide use. The study, to be published this week in an online edition of the "Proceedings of the National Academy of Sciences," found that native bees are capable of doing a lot more pollinating than previously believed. But it would take careful land use to take advantage of that capacity, the researchers concluded, because current high density, pesticide dependent agriculture cannot support native bees. "This is a valuable service that we may actually be destroying through our own land management practices," said Princeton ecologist Claire Kremen, who co-wrote the study with Neal Williams, a postdoctoral researcher, and Robbin Thorp of the University of California-Davis. Suppressing the many species of native bees and relying on just a few species of imported ones may be risky, said Kremen. Farmers who use managed bee populations - that is, most commercial farmers - depend on fewer than 11 species out of the 20,000 to 30,000 bee species worldwide. Other researchers have estimated that $5 billion to $14 billion worth of U.S. crops are pollinated by a single species of bee, the European honey bee. "Right now we are really very dependent on that species," said Kremen. "If something happened to that species and we haven't developed other avenues, we could really be in great difficulty." The researchers spent two years examining watermelon farms located at varying distances from oak woodlands and chaparral habitats that are native to the Sacramento Valley. They also looked at land that was farmed with pesticides and without pesticides. They focused on watermelon because it requires a lot of pollen and multiple bee visits to produce marketable fruit. They found that native bee visits dropped off in the farms that were distant from natural habitats and that used pesticides. "We could then multiply the number of visits by the number of [pollen] grains deposited per visit and sum that up for all the species and figure out how much pollen the watermelon plants were receiving," said Kremen. "We found that, where it still flourished, the native bee community could be sufficient to provide the pollination service for the watermelon." One interesting finding, said Kremen, was that the mix of native bees providing the pollination was very different in the two years of the study. In one year, a few strong pollinators accounted for most of it, while in the other, many species contributed. "That says something about the need for long term studies and also argues for the need to maintain diversity," said Kremen.