The latest environmental controversy in Tahoe isn’t a development project, a wildfire, or a fight over lake clarity.

It’s a weed killer.

A proposal to use glyphosate in portions of the Caldor Fire burn scar has triggered mounting concern among residents and environmental advocates, opening a broader conversation about the herbicide’s health risks, ecological impacts, and growing presence throughout the region.

It all started with nonprofit news outlet Mother Jones’ yearlong investigation into the expanding use of herbicides in California forests. Released in May, the article dove deep into the worlds of wildfire management and recovery, industrial pesticide production, and complex federal bureaucracy. Among other projects, the article highlighted Forest Service plans to use herbicide as a vegetation management tool in the burn scar of the 2021 Caldor wildfire.

The final environmental assessment and decision notice for the Caldor Fire Restoration Project — to be spearheaded by the Forest Service’s Lake Tahoe Basin Management Unit (LTBMU) — was released in March of this year. The project will thin tree stands in and around the burn area, remove damaged trees, and reforest burned areas, all within an approximately 11,700-acre project footprint.

Part of that preparation and reforestation is slated to include potential herbicide treatment. In the environmental assessment, LTBMU notes that “herbicides may be used to aid site preparation before tree planting and to manage competing vegetation after planting when manual treatments are ineffective or expected to be insufficient.”

At the top of the list of intended herbicides? Glyphosate.

Public reaction to the Caldor Restoration Project

The Mother Jones investigation analyzed more than 5 million California pesticide-use records, finding that approximately 266,000 pounds of glyphosate were applied in California forests in 2023 — nearly five times the amount used two decades earlier. The article characterized forest applications as the fastest-growing use of glyphosate in the state.

Public opposition to the use of the chemical in and around the Lake Tahoe Basin has quickly mounted, and pressure is on for local agencies.

In response to public outcry around the use of glyphosate in the Caldor Fire Restoration Project, a change.org petition began to circulate. It quickly garnered well over 22,000 signatures by the time this article was written, with public comments and support pouring in from across the country. Conspicuously absent from the body of this petition, however, are any concrete demands to address the titular demand, “Stop glyphosate spraying in the Tahoe Basin.”

This missing piece may be a reflection of the confusing decision-making associated with this project — in this particular instance, it seems few people know exactly how to effect change within our local bureaucracy.

Frustrated, concerned, and confused, the public has swarmed to social media and rallied at Tahoe Regional Planning Agency (TRPA) governance meetings to demand regulatory change. But that’s just not how it works, Jeff Cowen, public information officer at TRPA explained to me. At least, not anymore.

To understand the decision-making process behind environmental projects like this one, one must go back to the start. In 1969, TRPA was formed to help manage the two states, five counties, and three national forests that all wanted decision-making power over Lake Tahoe. Soon after, LTBMU was formed to consolidate national forest management in the region.

“It’s … been a partnership from the start,” Cowen said of the relationship between TRPA and LTBMU. But with 79% of land in the Basin owned and managed by the Forest Service, there are limitations on TRPA’s influence.

Those limitations have shifted over time, perhaps the most notable of which came as a result of the 2007 Angora wildfire. Inefficiencies, silos, and redundant regulatory procedures, Cowen explained, were identified as sticking points in the fire’s cause and magnitude. To address these hindrances, about 20 agencies came together to streamline environmental decision-making in the Basin.

Among the outcomes of this streamlining was an expanded memorandum of understanding between TRPA and LTBMU. For major projects like the Caldor Fire Restoration Project, TRPA is no longer a permitting authority, but instead an advisor to the decision-making process.

Cowen emphasized the efficacy of this decision, sharing that he feels that a “regulatory framework is really ineffective and not needed,” between the two agencies. “Because the Forest Service has very similar goals … they basically get to the point where they’re just adopting [our] goals and implementing them through their own plans.”

Together, the agencies have treated 80,000 acres across the Basin for wildfire prevention in the past two decades. But he also acknowledged there are “big, federal, overarching principles and direction that they also have to follow.”

As of late, these overarching principles seem somewhat murky.

How we got here: A noxious government love affair

In February of this year, the Trump administration made a sweeping move with the issuance of an Executive Order unambiguously named “Promoting the National Defense by Ensuring an Adequate Supply of Elemental Phosphorous and Glyphosate-Based Herbicides.”

This explicit prioritization of glyphosate production and use by the executive branch is a conveniently-timed declaration of support for the lawsuit-ridden Bayer company — and it’s no mystery as to why, Nathan Donley from the Center for Biological Diversity explained.

Our government has and continues to validate the use of glyphosate and other pesticides — despite the widely documented risks — because of the immense lobbying power of agricultural and agrochemical industries, Donley said. And it is far from isolated to the Trump administration.

“It’s been an absolute full court press from Bayer on all levels of government,” he explained. “Not just the executive and legislative branches. I mean, Clarence Thomas was a former Monsanto employee.”

And he’s not the only agrichemical-employee-turned-political-appointee. As of President Trump’s first year in office, all four of the top positions in the EPA’s Office of Chemical Safety and Pollution Prevention — the Principal Deputy Assistant Administrator, Assistant Administrator, Deputy Assistant Administrator for New Chemicals, and Deputy Assistant Administrator for Pesticides — have been filled by former executives or lobbyists of chemical and agricultural companies. The EPA and most other pesticide regulatory agencies continue to assert that glyphosate does not pose a health risk when used according to its label.

As Donley said, “the tendrils run deep … in the levels of influence that this company, Bayer, has in our government.”

Just how deep they run on initiatives like the Caldor Fire Restoration Project remains somewhat opaque. In the project’s environmental assessment, the herbicide use is identified as a way to expedite reforestation and “achieve silvicultural objectives.” These objectives? Conifer stands.

The assessment names three target species that, if not for herbicide use, could otherwise outcompete reforested conifers: western whitethorn, greenleaf manzanita, and ceanothus, or California lilac.

These native, fire-adapted species are known as pioneer species, meaning they are often the first to appear after wildfire events. Their fast-growing roots help to stabilize fire-impacted soil and prevent excess erosion, while also providing species-specific benefits like returning nutrients to damaged soils and quickly regenerating important habitat for pollinators and other species.

But while targeted elimination of native species may raise eyebrows, the Forest Service has an explanation. They are “not taking a wholesale targeting approach to these shrub species,” but instead targeting them only in the immediate vicinity of conifer seedlings. This will help ensure the area includes enough established trees to prevent full conversion to a montane chaparral environment, which could otherwise ignite easier and burn faster in future fire seasons.

Still, there is time before glyphosate use is slated to begin in the Basin.

“No herbicide application is planned for 2026 or 2027,” the Forest Service’s Region 5 media team stated. “Reforestation is an activity that will occur after initial entry (such as mechanical or hand treatments to remove overhead hazards and perhaps prescribed burning or mastication as site preparation) and occurs later in the project implementation timeline.”

Of the 11,700 acres of Forest Service land included within the project area, herbicide treatment is only proposed on a portion of the 2,400 to 3,600 acres where reforestation efforts will take place.

It’s a common pesticide. What’s the big deal?

Well, ain’t that the $11 billion question.

Health and environmental concerns associated with glyphosate use and exposure have been bubbling up for over a decade.

And despite being the most widely used herbicide globally, glyphosate wasn’t originally poised to become a pesticide at all. The chemical was first developed as a boiler and pipe cleaner agent. It wasn’t until 1974 that Monsanto, an American agrochemical and biotechnology company, discovered its efficacy as a herbicide. Monsanto quickly patented the discovery and sold glyphosate as the active ingredient in its crown-jewel herbicide product — Roundup.

For over 25 years, Roundup products filled shelves at hardware and home garden stores, farming co-ops, and major industrial retailers as the sole glyphosate-based product. Touting its unique success as a versatile weed-killer, products were marketed and sold in a variety of forms, from ready-to-use herbicides for home gardens to commercial-grade concentrates designed for agricultural, industrial, and heavy-duty landscaping use. The substance was applied with everything from handheld bottles to backpack devices to large-scale aerial sprayers.

In 2000, Monsanto’s patent for exclusive use of the chemical expired in the United States. Other manufacturers began to flood the market, introducing their own glyphosate-based herbicides. Public use skyrocketed and, for the better part of two decades, glyphosate products flew off shelves.

Then in 2015, the International Agency for Research on Cancer, an agency of the World Health Organization (WHO), published a scientific evaluation of the carcinogenicity of several market herbicides, glyphosate among them. As a result, glyphosate was designated as “probably carcinogenic to humans.”

Months later, the first lawsuit to allege Monsanto’s Roundup products were causing cancer proceeded to trial in the Superior Court of California, County of San Francisco. Dewayne “Lee” Johnson, a groundskeeper for Benicia Unified School District argued Roundup had caused his non-Hodgkin lymphoma. The case, Johnson v. Monsanto, became the first of approximately 125,000 similar claims filed by 2020, with the California court ultimately ruling in Mr. Johnson’s favor. The jury awarded the plaintiff $289 million in compensatory and punitive damages, an amount that was later reduced by the judge to $78 million and then $21 million.

At the same time, proponents of glyphosate products began to vehemently defend both its safety and usage.

One such advocate named Patrick Moore, a former environmentalist turned TED-talking-climate-change-skeptic, even went so far as to claim Roundup was safe to drink. Moore was featured on air in a CBC News segment on the 2015 WHO findings, where he stated that “you can drink a whole quart of [Roundup], it won’t hurt you.” However, when offered a glass of the chemical by his interviewer, Moore declined to substantiate his claim in real-time, repeatedly saying “No, I’m not stupid.”

In 2017, a multi-district litigation in the U.S. District Court for the Northern District of California consolidated the surge of federal lawsuits against Monsanto for its Roundup products. The litigation revealed a body of evidence that the leading study cited to defend Roundup’s safety for human exposure — Safety Evaluation and Risk Assessment of the Herbicide Roundup and Its Active Ingredient, Glyphosate, for Humans, published in 2000 by Regulatory Toxicology and Pharmacology — was in large part shaped and steered by Monsanto employees. The suit exposed email exchanges between Monsanto employees offering congratulations to one another for their “hard work” on the study and hopes that it would become “the reference on Roundup and glyphosate safety.”

Ultimately, the journal retracted the study, citing significant ethical concerns. But the damage was done, and the study still ranks among the top references justifying glyphosate use and claims to its safety.

In 2018, Monsanto was acquired by Bayer, a German pharmaceutical and agricultural chemical company. Bayer continued to sell Roundup but quickly discontinued the use of the Monsanto brand name, which was becoming increasingly tied to unfavorable litigation.

The United States District Court for the Northern District of California found Monsanto liable for another case of non-Hodgkin’s lymphoma in Hardeman v. Monsanto Co. in 2019, initially awarding Mr. Hardeman $80 million in damages — a total subsequently reduced to $20 million. The U.S. Court of Appeals for the Ninth Circuit upheld the decision in 2021, finding that the EPA’s approval of a pesticide label does not immunize a manufacturer from being held liable. This case ultimately became the first (and at this point, only) federal decision on the issue.

Despite Bayer phasing out glyphosate as an active ingredient in its residential Roundup products in 2023, it remains present in commercial and agricultural formulas. Lawsuits have continued to arise, with substantial damages and fees awarded to plaintiffs whose exposure to Roundup resulted in non-Hodgkin, follicular, T-cell, or other forms of lymphoma.

As of the time this article is being written, Bayer has paid over $11 billion in settlements for Roundup-related lawsuits and proposed a nation-wide class action settlement that would cap current and future claim payouts at $7.25 billion, to be used for declining payments for up to 21 years. The class action is heavily opposed by plaintiffs and environmental and public health organizations who have described it as a liability “shield.” A decision from the federal Supreme Court on its constitutionality is expected later in June. If approved, it will become one of the largest legal fee awards to date.

Public health and environmental impact

Cancer is far from the only public health risk posed by glyphosate use and exposure.

Studies have found potential ties between glyphosate exposure and various medical conditions such as liver disease and reproductive disorders including PCOS, endometriosis, and disruptions to fertility. What’s more, a growing body of research is finding that glyphosate exposure may be a trigger for various gastrointestinal diseases and conditions, including celiac disease, inflammatory bowel disease, and irritable bowel syndrome (IBS).

But despite these alarming associations, it remains unclear how much exposure is required to pose a real health risk to humans. In the vast majority of legal cases, affected plaintiffs are groundkeepers, farmers, or dedicated recreational gardeners — folks routinely subjected to highly concentrated forms of glyphosate.

In all likelihood, the exposure any individual may experience as a direct result of a relatively remote use such as the Caldor Fire Restoration Project would not cause substantial human harm. According to the National Pesticide Information Center, the half-life (time needed for a chemical to reduce to half of its initial amount) of glyphosate is particularly variable, landing somewhere between 2 and 197 days in soil, and between “a few days” and 91 days in water.

The chance of human exposure narrows further upon consideration of where the Caldor Fire Reforestation Project’s proposed herbicide treatment areas lie. In an email, the Forest Service’s Region 5 media team noted that “for the Caldor Fire Restoration Project, herbicide use is proposed only on a subset of the area proposed for reforestation, where other reforestation site preparation methods will not work. For example, manual removal equipment is not permitted in project areas with steep slopes, locations far from existing roads, [or] sensitive soils.”

But the questionable human health impacts of this project are not the sole consideration in this instance. An even greater risk is the ecological devastation that glyphosate wreaks on habitats, plants, and wildlife.

Donley at the Center for Biological Diversity noted that so long as glyphosate is present, it poses an environmental risk. This is particularly true after any precipitation, where stormwater runoff “goes into the nearby river, lake, or stream of that watershed and contaminates it with high pulses of pesticide.”

Donley emphasized that most animals do rely on these waters, whether they are woodland animals seeking drinking water, wetland species like migratory birds, or aquatic animals that then have no choice but to suffer through 24/7 exposure to contaminated water. While this can be lethal, he added, there are other effects as well. “It can lead to chronic harms like reduced reproductive capability or developmental defects, so it can affect subsequent generations and ultimately lead to population decline or even collapse for certain species,” he explained.

The Environmental Protection Agency found that glyphosate use was likely causing harm to 1,676 of the approximately 1,700 plants and animals protected under the Endangered Species Act.

Where the Caldor Fire Restoration Project is concerned, LTBMU will be taking some precautions to prevent this catastrophic runoff. “Herbicide applications will not take place within six hours of predicted rainfall that has a high probability of producing measurable runoff, or as requested by the Forest Service aquatics biologist,” the Forest Service shared via email. Additionally, the project will use backpack sprayers or other low-volume methods, as opposed to aquatic or aerial application, which produces greater concern for pollinator species.

But slip-ups or insufficient margins of time between application and precipitation could be catastrophic for some species that call the Tahoe area home.

In 2021, the federal Environmental Protection Agency found that glyphosate use was likely causing harm to 1,676 of the approximately 1,700 plants and animals protected under the Endangered Species Act. Impacted species include the Sierra Nevada red fox, California spotted owl, and Sierra Nevada yellow-legged frog, all of which are listed in the federal Endangered Species Act and live in our area.

Hitting close to home

While proposed glyphosate use in the Caldor burn scar has created quite a stir for the public, it appears as though our community remains blissfully unaware that glyphosate made its debut in the Truckee/Tahoe area long ago.

According to its most recent annual data, California’s Department of Pesticide Regulation (DPR) ranked glyphosate the sixth most used pesticide in the state in 2023. Of herbicides (plant-specific pesticides) used statewide, glyphosate ranked number one both by pounds applied and total acres treated – 10.7 million and 4.8 million, respectively. About 270,000 pounds alone were used to spray California’s forest land, a figure that has been steadily increasing each year.

Agriculture remains a top use, with glyphosate the pesticide of choice for a variety of crops, from cotton to nuts to citrus and even — put down your glass of pinot here — wine grapes. Neighborhood gardens also pose a risk; DPR data excludes residential use, but despite Bayer’s 2023 phaseout of glyphosate from its residential products, the compound remains the active ingredient in competitor products. Nationwide, the EPA estimates residential and non-crop glyphosate use at several million pounds per year.

While glyphosate is most closely associated with agriculture, it is also widely used in non-agricultural settings, including rights-of-way corridors, landscape maintenance, parks, athletic facilities, golf courses, utility infrastructure, and other managed public spaces.

Individual county reporting provides insight into current uses regionally. El Dorado County, which encompasses the Eastern side of Folsom to the California-Nevada state line in South Lake Tahoe, applied over 9,500 pounds of glyphosate in 2023 for forest and timberland applications, and just over 6,000 along rights of way areas like roads, highway corridors, sidewalks, and curb areas. Placer County, on the other hand, reported over 9,000 pounds used for rights of way areas, just over 4,600 pounds for forest and timberland areas, and just under 4,000 pounds for landscape maintenance. Nevada County clocked in with significantly lower rates, at  just over 2,000 pounds used for rights of way areas and a similar amount for landscape maintenance topping the list in 2023.

These numbers encompass more than public agency use. Private landowners are also obligated to report use to DPR, and glyphosate has become industry-standard for a number of vegetative fixtures. For example, on its website, NV Energy notes herbicide use as a mechanism for vegetation management under its power lines.

A recent follow-up article from Mother Jones opened with investigative journalist Nate Halverson standing in the middle of a run at Sierra-at-Tahoe that “clearly had been doused in glyphosate,” pointing to the area being “devoid of spring flowers; the bushes leafless, brittle, and dead by all appearances.” Sure enough, Halverson had found that the “Forest Service posted maps online showing it had sprayed glyphosate around and within Sierra-at-Tahoe in spring 2025.” This spraying was a part of a separate Caldor Fire Restoration Project, managed by El Dorado Resource Conservation District and taking place outside of the Basin, with a much larger footprint approved for herbicide use.

Patrick Lacey, public relations manager at Palisades Tahoe, said the resort does not use any chemicals, herbicides, or pesticides for vegetation management. Instead, he explained, its vegetation management crews use the mechanical removal of smaller trees and bushes to focus on “reducing ladder fuels on the forest floor and skier safety; the combination works synergistically.”

Marc McMullen, the golf course superintendent at Northstar California Resort, told me he does use glyphosate as well as fungicide to manage vegetation on the Northstar course. While total use during the season is relatively low, McMullen emphasized that the compound used is a harsh enough product that it is not available off the shelf and requires a pesticide applicator license through both the state and county.

University extension publications and turf-management literature routinely identify golf courses as a significant use category for the herbicide for vegetation management, cart-path edging, weed control, and renovation projects.

Moonshine Ink reached out to other land managers of community spaces, but many did not respond to the inquiries.

While debate continues over where and when glyphosate should be used, its presence in the modern landscape is difficult to avoid entirely. That reality raises a practical question for residents: What steps, if any, can individuals and communities take to reduce exposure?

Unless someone like you cares a whole awful lot

Options range from personal choices to participating in public discussions.

First and foremost, eating food grown using organic practices whenever possible is one of the leading ways to reduce glyphosate exposure and mitigate its harms to human health, researchers say.

A 2020 study published in Environmental Research found that diet is a main source of glyphosate exposure for humans. What’s more, researchers found glyphosate levels in children prior to making the switch to organic foods were approximately five times higher than adult levels. The good news? Transitioning to organic food had a near-immediate impact on the amount of glyphosate in subjects’ systems, reducing levels by over
70 percent.

Water, too, can be a potential source of glyphosate exposure. In the Basin, where most household drinking water comes from surface waters, regional water purveyors regularly test for pesticides. Sarah Vidra, the Executive Director at Tahoe Water Suppliers Association, confirmed that “pesticides are … monitored as part of the Synthetic Organic Chemicals (SOC) program.” Currently, she added, “the Association is not aware of any pesticide detections exceeding drinking water standards in Lake Tahoe source water supplies.” Vidra confirmed the SOC testing TWSA uses detects glyphosate.

Truckee tap water is substantially more removed from potential contamination, as the Truckee Donner Public Utility District (TDPUD) sources all water from deep underground aquifers. “The average age of our drinking water predates many modern chemicals,” Alex Spychalsky, TDPUD Communications Program Manager, explained via email. “For example, the rain we saw fall in our region last week won’t reach our aquifer for decades.”

But Donley said there’s more to be done than relying on water purveyors. “Regardless of how clean you think your water is, everyone should have a good water filter in their house,” he advised. “Because I don’t care how clean you think your water is, it’s not.”

While limiting glyphosate exposure in private spaces like kitchens, yards, and gardens can help mitigate risk, navigating more public areas that are outside of one’s control can be more complex. A simple rule of thumb, Donley suggested, is don’t play — and don’t let your loved ones play — where dandelions don’t grow. Weeds and other landscaping imperfections are natural. Allow them to be a sign of safe, glyphosate-free spaces.

Locally, questions about herbicide use may be addressed through existing regulatory and planning processes. As for the standards by which TRPA advises projects, those can be changed, though Cowen noted that “the path to what action [TRPA] can take is a relatively long one.” While it typically responds to emerging issues through scientific review, Cowen suggested the level of public interest surrounding glyphosate may warrant further examination. In the case of herbicide use in the Tahoe Basin, he said, “public concern is probably enough for us to start looking at it.”

Whether glyphosate is ultimately used as part of the LTBMU Caldor Fire Restoration Project remains to be seen. What is already clear is that the proposal has sparked a broader conversation about forest management, wildfire recovery, herbicide use, public health, and environmental stewardship — one that is likely to continue well beyond the boundaries of the burn scar itself.