Across the United States, wild canola grows in asphalt cracks and along roadways; it’s been found that this weedy plant often survives herbicide applications. Scientists at the University of Arkansas recently discovered why: About 83 percent of the weedy canola they tested contained herbicide resistance genes from genetically modified (GM), cultivated canola. Globally, canola can interbreed with 40 different weed species, 25 percent of which are found in the United States.

The findings raise questions about the regulation of herbicide- and pesticide-resistant weeds and about how these plants might compete with others in the wild. Nature reports that GM crops have spread beyond cultivated land in several countries, including Canada, Japan, the UK and the United States.