After an E. coli outbreak in bagged spinach in 2006, growers in California’s Central Coast were pressured to remove vegetation that bordered their fields as a way to keep out wildlife and prevent food contamination by pathogens. A study by the University of California says it didn’t work – E. coli contamination “in fresh produce increased by more than an order of magnitude from 2007 to 2013 despite extensive vegetation clearing at farm field margins.” In fact, vegetation clearing was associated with increased pathogen prevalence over time and pathogens were more common in fields close to grazing land.
“These findings contradict widespread food safety reforms that champion vegetation clearing as a pathogen mitigation strategy,” say the scientists. “More generally, our work indicates that achieving food safety and nature conservation goals in produce-growing landscapes is possible.” Claire Kremen, the senior author of the study, said there is strong evidence that natural habitats around fields help pollinating insects, and that studies suggest “a landscape with diverse plant life can filter out agri-chemical runoff and even bacteria. Changing this dynamic shouldn’t be taken lightly.”
While the outbreak was traced to a farm in the Central Coast, a region that grows 70 percent of salad vegetables in the country, the cause of the outbreak was not officially determined. Wildlife was blamed and removal of habitat was expected to deter the animals. Analysis of 250,000 tests of produce, irrigation water and rodents found no benefit from the costly and labor-intensive clearing of land. The correlation of pathogen levels and proximity to grazing land prompted the scientists to suggest ways that farming and ranching can co-exist.
Those steps include leaving strips of vegetation between grazed areas and fields growing fresh produce; fencing waterways so cattle waste is not washed downstream toward produce fields; and planting crops that are cooked before being eaten, such as corn or artichokes, between grazing areas and fields of fresh produce. Federal law is putting new emphasis on prevention of foodborne illness. “There is this misguided idea that agricultural fields should be a sanitized, sterilized environment, like a hospital, but nature doesn’t work that way,” said Daniel Karp, lead author of the study.