In the wake of a 2006 outbreak of E. coli -- spread via packaged spinach harvested on a farm in Central California -- farmers began clearing wild vegetation around growing fields.

Investigations weren't able to pinpoint the source of the outbreak, but many placed the blame of wildlife. But new research suggests restructuring the agricultural landscape to minimize wildlife is inadvisable and has no effect on the presence of pathogens like E. coli.

"Wildlife took much of the blame for that outbreak, even though rates of E. coli in wildlife are generally very low," Daniel Karp, a research fellow at the University of California, Berkeley, said in a press release. "Now, growers are pressured by buyers to implement practices meant to discourage wildlife from approaching fields of produce. This includes clearing bushes, plants and trees that might serve as habitat or food sources for wild animals. Our study found that this practice has not led to the reductions in E. coli and Salmonella that people were hoping for."

In a new paper in the journal PNAS, Karp and his colleagues posit that wildlife clearing may negatively affect farmland. Research has shown that natural vegetation can help sustain bee populations, vital for pollinating flowering crops.

"There have also been studies that suggest that a landscape with diverse plant life can filter out agrichemical runoff and even bacteria," said Claire Kremen, a Berkeley professor of environmental science, policy and management. "Changing this dynamic shouldn't be taken lightly."

Researchers arrived at their conclusions after analyzing more than 250,000 surveys of of crops, irrigation water and local rodents, in which samples were tested for pathogens. The scientists compared test results with land use maps, and found no correlation between pathogens and the presence of wild vegetation.

"Clearing surrounding vegetation is a costly, labor-intensive practice that threatens wildlife habitat," said Karp. "Since it does not improve food safety, there is no reason to continue this practice."