Painted signs began appearing along Sir Francis Drake Boulevard in Inverness this month: “No poison in our watershed.”
Then came an online petition, which, as of Wednesday morning, has gathered more than 1,100 signatures. And, last Sunday, at the annual Western Weekend parade, a man dressed as a sea otter sauntered down Main Street, lofting a sign emblazoned with “No Roundup.”
The alarm was triggered by a California State Parks wildfire-mitigation effort that could allow a toxic weedkiller that has been linked to cancer to be used near Tomales Bay and within parts of its watershed.
The plan, about seven years in the making, calls for a combination of manual removal, mechanical excavation, prescribed burns, and herbicide application across portions of Tomales Bay State Park’s 2,400 acres, which contain one of the world’s most extensive bishop pine forests. Herbicide use would be limited to fewer than six acres across the project area and applied by ground-based methods, such as backpack sprayers and cut-stump application.
But the plan’s mere mention of glyphosate—the active ingredient in what Monsanto first sold in 1974 under the brand name Roundup—is a cause of consternation in West Marin.
For now, the plan has no implementation date. It’s tied up in appellate court.
In 2024, two groups, Tomales Bay Forest Keepers and the California Chaparral Institute, sued State Parks in an effort to halt the project. They argued that the agency had failed to adequately assess the project’s impacts by relying on a statewide environmental review for wildfire-prevention projects, rather than preparing a site-specific environmental impact report.
In November, Marin Superior Court Judge Andrew Sweet denied the groups’ petition. They appealed this winter.
“It’s not only that glyphosate is toxic and should be used nowhere ever, but I don’t accept the diagnosis that this is anything but a really healthy, dense coastal forest,” said Jack Gescheidt, an animal rights activist who lives in San Rafael and is the sole named member of the Tomales Bay Forest Keepers. He contends that the plan would devastate the forest while offering negligible fire-safety benefits.
State Parks officials see a different forest. They say it’s plagued by an understory thick with dead trees, fallen branches, and dense mounds of dried needles. After decades of fire suppression, bark beetle infestation, and drought, old trees are failing and young trees are not growing up to replace them. Bishop pines regenerate through fire; heat melts the resin sealing their cones, which then crack open and scatter seeds across the forest floor.
State Parks officials declined to be interviewed, but they defended the agency’s vegetation management practices in a written statement.
“State Parks carefully considers and strategically deploys a variety of treatment options to manage vegetation—including combating invasive weeds that are highly detrimental to native ecosystems and creating defensible space between facilities and potential wildfires—while taking into account the unique environmental characteristics of each park within the nation’s largest and most biologically diverse state park system,” a statement sent to the Light said.
The Tomales Bay State Park Forest Health and Wildfire Resilience Project allows for the use of glyphosate, clopyralid, imazapyr, and triclopyr—herbicides that differ in plant selectivity and how they disrupt plant growth—to control invasive species such as jubata grass, cape ivy, eucalyptus, French broom, and acacia. The plan describes herbicides as a tool of last resort, to be avoided “to the maximum extent feasible” and used only “when other methods are not feasible due to their cost, effectiveness or environmental impact.”
The plan also bars herbicide near streams that support fish, drinking water, or other aquatic life, with no-spray zones ranging from 50 to 150 feet, depending on the particularities of the stream and the steepness of its banks.
The chemicals would also be prohibited within 50 feet of endangered or threatened plant species, and within 100 meters of northern spotted owl nests during nesting season. Application must stop if sustained winds exceed seven miles per hour, and it cannot occur during rain or within 24 hours of forecast precipitation. Signs listing the product name, active ingredient and application dates must be posted at treatment areas and trail intersections for at least three days after treatment ends.
Still, opponents say those guardrails do not go far enough, particularly in a park that drains into Tomales Bay and the Inverness watershed. They worry the chemicals could contaminate the community’s water source and the beaches where residents swim, and could move through the food web, harming wildlife.
The recent outcry began after Kristin Lawless, an Inverness-based journalist, read through the plan and was disturbed to find a section on herbicide use. She said she contacted State Parks but felt her concerns were brushed aside. Then she read a Mother Jones investigation about the wholesale use of Roundup by the U.S. Forest Service and CalFire in post-fire recovery areas.
“I realized this was a nationwide phenomenon where they are spraying forests with glyphosate,” she said. “It prompted me to dig a little more into what was happening locally. These are big problems, and what’s happening here is a small battle in a larger war.”
Ms. Lawless wrote an impassioned Substack post about the issue. After her friend Nichole Zlatunich, a 43-year-old painter who lives in Inverness Park, read it, she launched the Change.org petition.
“Releasing poison into our environment, where people are swimming and drinking water, is just absolutely crazy,” Ms. Zlatunich said. “We don’t want this here.”
The safety of glyphosate has been hotly debated for decades. A growing body of research suggests the chemical may play an insidious role in cancer and chronic disease, though the science remains far from settled.
The World Health Organization’s cancer agency classified it in 2015 as “probably carcinogenic to humans.” A few years later, the Environmental Protection Agency concluded it was not likely to cause cancer when used according to the label. (The E.P.A. faces a deadline this year to reconsider the safety of the weedkiller after legal action brought by environmental and farmworker advocacy groups. But any reassessment will unfold against the backdrop of a February executive order from President Trump compelling the domestic production of glyphosate and declaring it “critical to the national defense.”)
The same year as the W.H.O. determination, Marin County banned glyphosate on county-maintained parks, playgrounds, walkways, and parking areas. In 2018, Point Reyes Station’s Building Supply Center stopped carrying products that contained the chemical.
The National Park Service, meanwhile, has used herbicides, including diluted glyphosate, for decades at the Point Reyes National Seashore to control invasive plants. “Herbicide application is part of regular work conducted within the Seashore and many units of the National Park Service,” park spokesman Earl Perez-Foust wrote in an email to the Light.
Glyphosate, which kills weeds by inhibiting an enzyme that is essential for plant growth, is the most widely used herbicide on earth. In 2024, more than 280 million pounds were sprayed on American farmlands, according to the U.S. Geological Survey. Non-agricultural applications by homeowners, parks, schools, and forest and range managers increased 43-fold between 1974 and 2014, as the chemical became a blockbuster product.
Tens of thousands of plaintiffs, including farmers and gardeners diagnosed with non-Hodgkin lymphoma, have sued Monsanto alleging that Roundup caused their cancer. In an early case, in 2018, a jury awarded $289 million to Dewayne Johnson, a Bay Area school groundskeeper, after concluding that glyphosate had caused his cancer. Monsanto, jurors said, had failed to warn consumers of the risk.
Bayer, the pharmaceutical and agrochemicals giant that acquired Monsanto in 2018, has paid more than $12 billion to settle roughly 100,000 Roundup claims. The settlements have not included admissions of liability or wrongdoing, and Bayer continues to sell the product.
Dr. Andrea Gore, a professor of pharmacology and toxicology at the University of Texas at Austin, said cancer concerns are generally associated with higher exposures, such as those experienced by agricultural workers and people who live near heavily treated fields. Lower-dose exposures raise different questions, particularly around hormone disruption.
“We think that glyphosate is an endocrine-disrupting chemical,” Dr. Gore said. Endocrine disruptors can interfere with the hormones that regulate fertility, metabolism, and brain development, raising a myriad of health concerns.
She said much of the public debate over glyphosate’s safety stems from the fact that manufacturers have relied on internal laboratory tests and studies by their own scientists to support claims that the chemical is safe. In her view, that has created a false impression of scientific disagreement.
“That’s the fox guarding the henhouse,” Dr. Gore said. “As a consumer, I would prefer to have an independent body determine whether a chemical is safe before it’s introduced into the environment and the food supply.”