DAVID GREENE, HOST:
And now let's hear why vegetable farms are becoming scenes of confrontation, pitting humans against wildlife. Some farmers have been wiping out trees and clearing the land around their fields. They're hoping to keep mice and other animals out of their crops. It's an effort to make food safer. But critics have pointed out something important - none of this seems to be working. Here's NPR's Dan Charles.
DAN CHARLES, BYLINE: This battle started nine years ago when disease-causing E. coli bacteria got into bags of spinach from a farm in California and made 200 people sick. Three of them died. Investigators went looking for the source of the contamination. Daniel Karp a biologist at the University of California, Berkeley says the investigators found matching bacteria in cattle living a mile or so from the farm. And matching bacteria also turned up in some wild pigs living right nearby.
DANIEL KARP: And the wild pigs were sort of the kicker because that led industry to suspect that wildlife were playing a major role of bringing these pathogens onto the farm field.
CHARLES: Ever since then, farmers have been getting rid of places where wildlife might hide. They've torn out trees, cleared stream banks, created wide strips of bare earth all around their fields. Environmentalists have been complaining that all this habitat destruction is based on fear, not scientific evidence of any risk to food safety. So Daniel Karp and a group of colleagues decided to look at the evidence. They analyzed thousands of test results from fresh produce from dozens of farms. And Karp says vegetables that grew near wildlife habitat were not more likely to be contaminated with disease-causing bacteria.
KARP: And in fact, you see no relationship. You do not see that the farms that are more near a habitat have any elevated levels of these pathogens.
CHARLES: Actually, he says, as some farms cleared away wildlife habitat, contamination with E. coli became more common.
KARP: So not only was it not working, it in fact to looked like it was making food less safe.
CHARLES: His study was just published in the proceedings of the National Academy of Sciences. Trevor Suslow, a food safety expert at the University of California, Davis, says quite a few researchers are coming to similar conclusions, and the industry is reacting. Practices are changing.
TREVOR SUSLOW: There's a lot more emphasis on actual visual evidence of animal intrusion into a field, as opposed to the presence of animals surrounding that field.
CHARLES: But this is a really tough problem to solve. No matter what they do, cases of contamination, though rare, keep happening. Dan Charles, NPR News.
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