Government agencies in the U.S., Canada and Mexico can’t say for sure whether the herbicides they spray on pubic lands to control invasive species are doing more harm than good, according to a new study by researchers at the University of Montana and their Canadian colleagues. The huge amount of herbicides applied by land managers every year—largely glyphosate (the key ingredient in Monsanto’s Roundup)—may in fact prevent native species from germinating.
“In 2010, 1.2 million acres of U.S. federal and tribal wildlands—an area the size of 930,630 football fields—was sprayed with 200 tons of herbicide,” says The Missoulian. The study, which was published in the Journal of Applied Ecology, found that neither Canada nor Mexico maintain records of herbicide use in invasive-plant management. In the U.S., only five of seven agencies did, and only four of them—the Bureau of Indian Affairs, the Bureau of Land Management, the Fish and Wildlife Service and the National Park Service—agreed to share those records. The U.S. Forest Service, which maintains more than a quarter of all the country’s public lands, refused to make its records public, citing concerns over the quality of its data.
Cara Nelson, one of the UM researchers on the study, believes that herbicides have their place in the effort to control invasive species. But “if native plants don’t establish after spraying, there is a high probability that undesirable plants will colonize and these so-called ‘secondary invaders’ can have even more detrimental impacts than the plant that was the initial target for control,” she said.