In California, Sonoma County voters appear to have banned genetically modified crops in unincorporated areas of the county, approving Measure M by a margin of 56-44 percent in unofficial results.

The results reflect a significant change in public sentiment. Sonoma voters shot down a similar measure in 2005 by a 5 percent margin.

Sonoma County joins five other California counties that have already passed bans on transgenic crops: Mendocino, Marin, Trinity, Humboldt and Santa Cruz.

Proponents say the ban is necessary to protect the county’s organic fields from cross-pollination.

Under U.S. law, says Karen Hudson, head of the campaign for the measure, if 1 percent of a farmer’s crop is contaminated by genetically engineered pollen, it becomes illegal for that farmer to use the seeds for the following year.

Hudson also worries about increased use of herbicides in GMO plants. Many of them are engineered to resist herbicides like Roundup.

Under the measure, farmers could not plant any GMO seeds or grow GMO crops in unincorporated areas, which includes the majority of vineyards, dairies and farms in the county.

Measure M allows a transition period so that growers could continue cultivating existing GMO crops until the plants mature.

Farmers who have GMO seeds in their possession would have to plant them in the growing season after the ordinance goes into effect. After that season, the GMO seeds would have to be destroyed or removed from the county.

The chemical companies Monsanto, Syngenta, Bayer, BASF, and DuPont funded the No campaign on Measure M.

“The growing method is considered safe and very effective,” says Dave Kranz from the California Farm Bureau. “You don’t know what may be coming when you impose a blanket ban.”

Kranz uses the example of transgenic papayas in Hawaii to make his point. When the ringspot virus almost annihilated the fruit in the 1990s, the rainbow papaya saved the day. The genetically modified fruit rejected the pathogen.

Earlier this year the National Academy of Sciences released a report concluding that genetically engineered foods are safe to eat.

“In some cases technology is a perfectly appropriate solution,” says Kranz.

He highlights the fact that Sonoma County is a grape-growing region that may need biotech to help vines weather severe droughts.

The ordinance would take effect as soon as election results are finalized, which is expected in early December.