The threat to public lands posed by invasive plant species is increasing by about ten million acres each year, and conservationists fear they will lose their best tool to combat it.
That’s according to data from the Bureau of Land Management (BLM) which manages 245 million acres of public land—about one in every 10 U.S. acres.
As pressure from invasive plants grows, conservation groups and land managers worry that glyphosate, the active ingredient in Roundup, might soon be off limits or severely curtailed.
“As it stands, glyphosate is really the best tool we have for fighting invasive plants,” said Brendan Quirion, an invasive species specialist with The Nature Conservancy, the largest conservation advocacy group in the world.
The safety of glyphosate, developed by Monsanto, which is now owned by Bayer AG, has been disputed by scientists and regulatory bodies.
Across the six-million-acre Adirondack Park in Upstate New York where Quirion is based, The Nature Conservancy has removed over 1,000 infestations of invasive plants such as phragmites and Japanese knotweed, he said.
According to one report, the annual cost of controlling Japanese knotweed in the U.K. alone costs their economy around $214 million.
Bans and Restrictions
Farmers have been spraying glyphosate on their fields for decades, thanks to its low cost and effectiveness. But it has been dogged by emerging fears that at sufficient exposure levels, it may cause cancer.
The European Union came close to banning glyphosate in 2018 but opted instead to grant a five-year extension for the use of the product. A number of European countries including France, Belgium, Germany, Sweden, and the Netherlands have all passed their own restrictions.
In 2018, glyphosate was added to California’s official list of chemicals known to cause cancer. That move has since prompted dozens of local governments to ban glyphosate spraying in public school districts, parks, and gardens, and in some cases, private property.
California’s warning followed a similar one by the World Health Organization in 2015, which found that glyphosate was “probably carcinogenic to humans.”
Despite the more recent concerns, most of the world’s top regulatory agencies have found it to be among the safest herbicides on the market—a fact that Bayer officials continue to emphasize.
More Invasive Weeds
In recent years, California has been fighting a raging battle with non-native aquatic weeds, which now cover one-third of the Sacramento-San Joaquin Delta, the nexus of California’s statewide water system.
“Back in 2014-2015 we really had a crisis on our hands with water hyacinth,” said John Madsen, a California-based weed scientist with the U.S. Department of Agriculture.
Madsen said water hyacinth—along with several other aquatic invasives—have been choking harbors, snarling boat propellers, and contributing to declines in fish populations in the delta.
“If we don’t have glyphosate available, we’ll either have to switch to newer herbicides that are much more expensive, which means less acres controlled, or we’ll have to go with chemicals that are more concerning from a toxicological standpoint,” he said.
Spurred on by a number of factors including increased global trade and climate change, invasive species have emerged as a growing threat to human livelihoods and biodiversity generally.
“In 2000 we inventoried the presence of invasive and noxious weeds on 35 million acres of BLM land,” said Gina Ramos, a senior weeds specialist with Bureau of Land Management.
“When we updated the inventory in 2014 the number went up to 79 million acres,” or more than double the acreage, she told Bloomberg Environment.
The bureau’s integrated pest management program employs a three-pronged approach to pesticide use, together with mechanical and biological methods of weed control, such as introducing species that feed on invasive plants.
But unlike other herbicides, Ramos said, glyphosate works well on almost any plant and has the added benefit of killing them at the root level, eliminating the need and cost of going back to apply more chemicals.
Divisions in Conservation Community
The public row over glyphosate also has brought out divisions within the conservation community between those who want to preserve access to the chemical for habitat restoration and preservation, and anti-GMO activists and pesticide protection groups.
“We know that glyphosate is a probably carcinogen and a chemical that harms soil health,” said Marcia Ishii-Eiteman, a senior scientist at the Pesticide Action Network.
In an emailed statement, Ishii-Eiteman pointed to new evidence of the emergence of glyphosate-resistant superweeds.
“Rather than relying on a harmful, likely carcinogenic, and increasingly ineffective herbicide that poses a serious threat to public and ecosystem health, we need to ground efforts to restore habitat and manage invasive plants firmly in an ecological approach to plant pest management,” she said.
But others maintain that the limited application of glyphosate to control invasive species on public lands has little connection with broader concerns such as its use in agriculture.
“I think we need to fully consider both the ecological and societal impacts of not having this tool,” said The Nature Conservancy’s Quirion. “And then compare the risks of using a small amount of herbicide, versus the much greater impacts of having invasive species spread across the landscape.”
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