Monsanto Roundup Is Used on Wildlands, but No One Knows How Much
As I write this, I’m looking out at a salt marsh that requires regular spraying with the herbicide glyphosate (sold by Monsanto as Roundup) to keep it from being smothered under dense, eight-foot-high stands of an invasive grass called phragmites. At a nearby lake where I’m a member of a rowing club, the aquatic vegetation is now so dense that it’s being treated with another herbicide called flumioxazin. And along the roads back and forth, even more herbicides get applied, to keep down weedy vegetation along the edges.
More than 50 years after Rachel Carson’s Silent Spring first raised the alarm about their uncontrolled use, herbicides are everywhere in North American life. Use of glyphosate alone has increased 15-fold since the introduction of genetically modified Roundup Ready crops in the 1990s. In 2014, that worked out to 250 million pounds of the stuff—eight-tenths of a pound for every acre of U.S. cropland. And it’s not just about agriculture.
A new study in the Journal of Applied Ecology attempts for the first time to add up herbicide use on North American wildlands. “The numbers are much less than those for croplands, but they are astonishing,” said lead author Viktoria Wagner, a plant ecologist at Masaryk University in the Czech Republic. She and her coauthors found reliable information on just 1.2 million acres of wildlands, a fraction of the U.S. government’s 640 million acres of parks, forests, refuges, and rangelands. But in a single year, that sample was sprayed with a total of 443,000 pounds of herbicides—equal, said Wagner, to “the weight of 13 school buses.”
The new study isn’t necessarily aimed at stopping herbicide use. Land managers have an obligation to take action against invasive species that would otherwise devastate native ecosystems, said Cara R. Nelson, a coauthor and a restoration ecologist at the University of Montana.
For instance, cheat grass, an Old World species that has run wild across the American West, destroys the food value of rangelands for wildlife, particularly dwindling populations of greater sage grouse. It also causes big, hot wildfires that kill off sagebrush, depriving the sage grouse of shelter. Fast-growing kudzu, “the vine that ate the South,” smothers native plant species and pulls down trees. Water hyacinth chokes ponds and lakes everywhere. Ending herbicide use would just speed up the pace of destruction.
What worries the team of coauthors, including researchers from Mexico, the United States, and Canada, is the almost complete lack of record keeping in those three countries detailing where herbicides are being used on wildlands, in what quantities, at what cost—and to what effect. So there’s no way to tell if herbicides are doing the job—or if they are incidentally damaging native species. “The point of our paper,” said Nelson, “is that we’re using a very large amount of herbicide” on wildlands in an attempt to restore native species, “but we know almost nothing about effects on native plants”—or, for that matter, on pollinators and other native wildlife.
The experience in agriculture suggests this could pose a significant risk: Intensive use of glyphosate on farms has, for instance, incidentally destroyed tens of millions of acres of native milkweed. To farmers, it’s just another weed, as the name suggests. But it’s an essential food source for monarch caterpillars, and loss of that habitat appears to be a major factor in the dramatic decline of the butterfly species.
Glyphosate is also the herbicide of choice on wildlands, a surprise, said Wagner, because it’s “a nonselective herbicide that harms grasses and herbs alike and thus has a higher potential to negatively affect desired native plants.” When she and Nelson made a separate study of two other commonly used herbicides, they found that both inhibited germination of native and invasive plant seeds alike.
“That’s important,” said Nelson, because spraying herbicides to remove invasive species “opens up ecological niches” for other plants—and restoration ecologists generally aim to fill those niches by planting seeds of native species. The United States spends billions of dollars on such ecological restorations every year. But right now, we are spending that money blind.
Both the U.S. Forest Service and the Bureau of Land Management, the two largest land managers in the country, are working to change that. The BLM last year launched its National Invasive Species Information Management System, an attempt to standardize collection of data on invasive species treatments.
But my guess is that Rachel Carson would say this is too little, too late, and that we need to be think much harder about what that 13-school-bus load of herbicides—multiplied across hundreds of millions of acres of North American wildlands—is really doing to our native species.