A female broad-tailed hummingbird feeds in Colorado. (David Inouye/U.S. Geological Survey)

This story was updated Sept. 7, 2021, to include links to the comment documents obtained by WyoFile.

Conservationists are criticizing a plan by the Bighorn National Forest to use aerial spraying to kill mountain big sagebrush and larkspur, native plants the critics say shouldn’t be destroyed to improve grazing for domestic stock.

The Forest Service plan also would spray toxic chemicals to fight infestations of the exotic noxious weeds ventenata and medusahead, which increasingly ravage the landscape. Administrators of the 1.1 million-acre forest have collected comments on a 246-page draft environmental study that proposes the action, drawing support from stock growers along with the environmental criticism.

The primary purpose of the proposed program is to combat the invasive plants, the Forest Service says in its draft environmental impact statement. Aerial spraying would allow the agency to “redeem its shared stewardship responsibility,” according to the document.

Sagebrush thinning, which critics say will amount to a 40% reduction of mountain big sagebrush in the area, would be undertaken by mowing, burning and poisoning “to achieve desired resource conditions,” the study says. Larkspur, a native plant that can poison cattle and that some of the Wyoming counties underlying the Bighorn National Forest have declared to be noxious, would also be targeted.

The Wyoming Stock Growers Association largely supports the plan, Executive Vice President Jim Magagna wrote, as does the Wyoming Department of Agriculture. In addition to backing the fight against the invasive species and the use or aerial spraying, the WSGA believes thinning mountain big sagebrush “is essential in … maximizing available forage for both livestock and wildlife.”

Four conservation groups oppose elements of the plan, including aerial spraying and the targeting of larkspur and sagebrush.

“That some Wyoming counties have declared larkspur a ‘weed’ is irrelevant,” Forest Service Employees for Environmental Ethics wrote. “Counties have no legal jurisdiction over our national forests.”

The Bighorn Forest has “a fictional understanding of sagebrush ecology,” Western Watersheds Project stated, as it unleashed a broadside against the proposal. The underlying problem is too much grazing, the environmental group said.

Bird lovers weighed in, too.

“Treating sagebrush and removing larkspur are not beneficial to the myriad of sage-dependent birds that inhabit the sagebrush-steppe,” the Council for the Bighorn Range wrote. The Bighorn Audubon Society called the proposal to thin sagebrush “a very unreasonable plan that purposely further reduces bird and other wildlife habitat.”

Three alternatives

The Bighorn National Forest stretches 80 miles from Ten Sleep north to the Montana border, and its 30-mile width covers parts of Sheridan, Washakie, Big Horn and Johnson counties. According to agency protocol, the Bighorn will finalize its decision after analyzing comments made on three alternative scenarios. 

The proposed plan is the agency-preferred alternative. The others include holding the course — a “no action” alternative — and thinning invasives, larkspur and sage brush without aerial spraying.

The Bighorn National Forest illustrates what it considers an undesirable condition of sagebrush cover with this photograph. (Bighorn National Forest)

The Bighorn can’t spray herbicides from the air without completing the analysis. Under the agency-preferred alternative, the Bighorn would attack the invasives and sagebrush, each at a rate of about 5,000 acres annually.

“Invasive plant species like the Medusahead and Ventenata grasses threaten native plant and wildlife habitat, undermine the health of watersheds, and increase wildfire risk,” the Bighorn said in calling for comments. “Sheridan County treated 28,000 acres of Medusahead and Ventenata grasses in 2020,” it said, underscoring regional worries.

Some underlying counties designated larkspur as a weed “because of its toxicity to grazing livestock,” the study says. Thinning sagebrush also is warranted, according to the study.

“Mountain big sagebrush treatment is done to create a mosaic of openings within dense sagebrush cover” to benefit several wildlife species, Thad Berrett, project leader for the Bighorn, said in a statement. Treatment is intended to “temporarily reduce sagebrush canopy cover,” growth that would reestablish itself in 30-40 years.

The Bighorn seeks to accommodate 113,800 Animal Unit Months of grazing, according to the draft impact statement. An AUM is the amount of forage a cow and a calf consume in a month.

Done properly, grazing has no negative impact on the environment, Wyoming’s agriculture department suggested as it challenged elements of the plan that characterized “cumulative effects” of running stock on public land.

“WDA recommends that anywhere the cumulative effects of livestock grazing is addressed that it be changed to ‘improper livestock,’” grazing, the state agency wrote.

Stockgrowers’ Magagna urged the Bighorn to “employ all available resources” to destroy the maximum amount of sagebrush annually that the study contemplates — 5,100 acres. That and other “treatment” goals can’t be achieved without using aircraft, which the Forest Service would employ for spraying and distributing biological controls.

Wyoming Game and Fish Department supports the proposed Bighorn plan, agency Habitat Protection Supervisor Amanda Losch wrote. The Forest Service should strive to use burning, rather than chemical spraying of sagebrush, because “the results are generally more beneficial to wildlife species,” her letter says. 

The wildlife agency wants to be engaged as the Bighorn adapts and changes strategies when it implements its yearslong program, she wrote. Game and Fish also wants appropriately robust monitoring before and after sagebrush is killed to ensure wildlife benefits.

Sagebrush sea

Sagebrush landscape covers about 15% of the Bighorn National Forest — some 163,000 acres — according to the draft study. The Bighorn plans to treat about 42% — some 68,000 acres — of mountain big sagebrush, the study says.

The Forest Service has been burning an average of 591 acres of sagebrush annually over about the last about 14 years, according to the study. Under the proposed plan, the amount to be thinned would increase to a maximum of 5,100 acres a year.

The Bighorn National Forest illustrates what it considers the desirable condition of sagebrush after thinning with this photograph. (Bighorn National Forest)

The plan to control invasive weeds would cover another 5,310 acres a year, 1,000 acres of which would be attacked by aerial spraying. For the invasive weeds, the forest would use the herbicides imazapic and indaziflam.

To kill sagebrush, the Forest Service would use, among other tools, the herbicide tebuthiuron, which is banned in Europe. The goal is to “mimic the sagebrush-to-grass/forb historical pre-fire suppression conditions,” the study says. Decades of fighting fires allowed the sagebrush fields to become denser, the study implies. 

The level of grazing today is “far beyond what the ecosystem could support,” Western Watersheds Project said in its comments. “The ‘desired conditions’ invented by the Bighorn have no basis in the best available science on sagebrush ecology,” the group’s Wyoming director, Jonathan Ratner wrote. “They are simply created to support the Forest’s severe overstocking problem, without doing anything that may displease its [grazing] permittees.” 

Killing sagebrush with tebuthiuron is “Neanderthalic,” Ratner wrote, and the Forest Service has no authority to use the chemical on the native species. The Bighorn also didn’t address how adding more of the herbicide to existing amounts in the area might affect human health, Andy Stahl, the executive director of FSEEE, wrote.

The critics also said thinning sagebrush could harm greater sage grouse and referenced studies that advocated against reducing mountain big sagebrush because of the deleterious effect that would have on the imperiled ground-dwelling bird.

Larkspur, the purple flower, and licorice root in Wyoming. (Susan Marsh/U.S. Forest Service)


Stahl also panned the plan to target larkspur, “a native plant with attractive blooms that appeal to national forest visitors.” Larkspur is a “high-protein, nutritious, and palatable species for wild herbivores,” he wrote.

Hummingbirds, too, feed on larkspur, Bighorn Audubon and the Bighorn Council said in a letter to supporters. Broad-tailed hummingbirds “drink nectar from the flowers and pollinate them,” the letter reads.

Larkspur isn’t the interloper, FSEEE said. “Livestock are an invasive species on the Bighorn,” Stahl’s comment letter reads.

Critics charged that the Bighorn doesn’t have an accurate inventory of invasive species. “The DEIS lacks even a map of current infestations, let alone any actual data,” WWP’s Ratner wrote.

The critics framed their complaints in an ecosystem context. “We ask that you do no harm to the ecosystem as you seek to control invasive plants,” FSEEE said in its comments.

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“Forest birds are in decline,” Bighorn Audubon wrote, “with over one billion North American forest birds lost since 1970, and a 30% (2.9 billion) overall loss of wild breeding bird adult populations. Habitat loss is likely a driving factor, particularly agricultural intensification and development,” the group said.

The Council for the Bighorn Range accused the Forest Service of kowtowing to one interest group. “The management of our public lands needs to reflect the actual full multi-use public policy, not just harnessing our land to one industry or use,” Rob Davidson, president of the council wrote.

Angus M. Thuermer Jr. is the natural resources reporter for WyoFile. He is a veteran Wyoming reporter and editor with more than 35 years experience in Wyoming. Contact him at angus@wyofile.com or (307)...

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  1. The Bighorn National Forest is not listening to people other than the subsidized cattle and sheep ranchers. We have been telling USFS for years that this type of range destruction is a terrible mistake. If you want to see resource damage just go to creek bottoms and marshy areas in the high country. Why should we want more of them? Tourism and wildlife generate a lot more income than grazing. This proposal is absurd.

    The BLM office in Worland once printed out a map layer for me which showed the historic prescribed burns they had done in the Western part of Hot Springs County and southern part of Park County – the Absaroka Front region. This was about 14 years ago and the burns totaled 55,000 acres of BLM land. By now, it must be about 65,000 acres. The concern was the large amounts of juniper and limber pine invading the area – prime winter habitat for elk, deer and antelope. The ranchers typically try to leave about 45% of the forage for the wildlife in that area but more forage was desirable. I remember the BLM implementing 1-3 prescribed burns per year using their existing staff and equipment.

    So why can’t the Forest Service utilize prescribed burns for sage brush control instead of spraying – after all the BLM uses burns. The Forest Service would have more support for the sage brush project if it was presented as a wildlife habitat improvement project not an AUM improvement project. The BLM burns I mentioned where primarily for wildlife and centered on critical winter habitat. Sure, the cattle benefited but that was a side issue not the main driver. It can be done that I know for sure.

    The Big Horn Mountains contain very important municipal water sheds; that is, areas where the runoff from the forest becomes the source of municipal drinking water for the towns on the edge of the Big Horns. Examples are the City of Buffalo’s water shed west of town, Sheridan and Ranchester’s water sheds, the Spanish Point karst AREA OF CRITICAL ENVIRONMENTAL CONCERN above Hyattville which recharges the Madison formation and thus the artesian well supplying Worland. My concern is that spraying in the forest may directly affect the drinking water for these towns and cities. and in addition, may be toxic for the fish in these streams flowing from the Big Horns. Very probably, the spraying chemicals are carcinogenic organic compounds which traditional water treatment plants are not capable of removing – most rely on chlorine and fluorine to kill living organisms but organic compounds are a different story. This is a very serious matter which these towns should thoroughly investigate – just where are the treatment areas with respect to their source of water?? I would be interested in seeing the EPA’s comments about this proposed chemical application. This is a serious matter – prescribed burns are a much better alternative.

  4. Angus, Please supplement this story with numbers. How much will this cost, and who pays? Who, and how many, will benefit, and how much will they get? How does the agricultural contribution to the economies of these four counties compare to the share from tourism? Will tourism suffer when the spraying of this toxin is publicized.:
    “The Environmental Protection Agency considers tebuthiuron to have a great potential for groundwater contamination, due to its high water solubility, low adsorption to soil particles, and high persistence in soil (its soil half-life is 360 days).” from wikipedia

  5. We often hear about todays ranchers being the “original stewards of the land” Why then did overgrazing by their grandfathers result in the Taylor Grazing Act of 1934?

  6. Cowboys, what are you going to do with your cows when the range is completely taken over by cheat grass, medusahead and other non-native invasive species? Are you willing to fully fund the total costs of treatments to eliminate these invaders? If not, remove your livestock from public lands before they further degrade the native range. It is past time for you to wean yourself from the public teat.

  7. It is not often that we all agree is it???

    In this case we all do. Poison is poison. It does not discriminate. It kills.
    This is sheer madness.

  8. Cancer is ravaging the nation. Increasingly, younger and younger Americans are diagnosed with cancers. I personally have tried far infra-red saunas trying to get the organic chemicals out of my body including spraying weeds for two summers. Controlled burns should be the preferred alternative and toxic chemicals totally rejected. How long do these herbicides remain in the ground before breaking down?? Everyone should read the book ” Detoxify or Die ” which details the poisoning of the American people. I am a Vietnam vet who was exposed to Agent Orange and fully understand the health impacts of spraying chemicals, and yet, our government continues to utilize toxic chemicals mindlessly. Have you noticed how the average life span of Americans has been dropping lately?? At one time, smoking was the culprit, but today, its exposure to thousands of toxic chemicals and heavy metals such as cadmium, lead, aluminum, arsenic and mercury. Our life spans are decreasing due to chemical poisoning – and many of these chemicals are not metabolized in our bodies and end up being stored in our fat, heart and brains. Will we never learn!!!

  9. Wyoming Stockgrowers Association is at full war footing against sagebrush and the Bighorn NF seems to be the proving ground. Magagna’s statements bear out the assertion that the use of herbicides against these native plants is solely for the production of forage for industry and not the health of range or the wildlife that depend on it. Mountain Big Sagebrush on the Bighorn National Forest has only increased three percent since the 1920’s (1997 BNF). The greenies and wildlife folks are not wrong.

  10. All the cattle and sheep grazed on public lands in Wyoming could disappear tomorrow and they would barely be missed a month from now …

    In all serious now, it should be obovious that the time has come to remove the Forest Service from the US Department of Agriculture , and combine it with the Bureau of Land Management , Park Service, Fish & Wildlife Service et ux in a new omnibus Department of Natural Resources.

    Climate Change pretty much demands we do this , or else suffer more of the consequences we are already sowing and reaping .

  11. That notion of a ” fictional understanding of sagebrush ecology …” extends a heckuva lot further than some public grazing allotments up in the Big Horns. The floors of the state Senate and House chambers and the Governor’s carpet come to mind …

    Wyoming’s cultural narrative and revisionist history dogma are also prime habitat for it. Who knew the Wyoming Stockgrowers had such a pantheon of noted scholars going back nearly 150 years ? Fictional understandings are the bedrock of the Cowboy State from coast to coast across the sagebrush sea…

  12. We wonder why cancers, autism and others diseases are on the rise in our population. Europe has banned this poison that will be sprayed to kill sagebrush because …….. Europe knows this stuff is toxic and gets in our food and water.

  13. Absolutely bad plan. Cattle and sheep are indeed the “invasive species” here. It is incomprehensible to institute a plan that would imperil bird species, seek to control a native species (Larkspur) and spread a poison into a National Forest that has been banned in Europe. I guess money does speak louder in America. Terrible plan for the Bighorn. Federal employees with lots of time on their hands and hoping Magagna will send them a card on Christmas. Why are all the Federal agencies in Wyoming always kow-towing to industry? No spraying of poison or increasing AUM’s in Wyoming should be the credo of the day. Cows and sheep already eat everything and leave paltry bits for wildlife. This needs to change completely. BS

  14. Spraying poison across our Public lands, what a wonderful idea! Now we can increase overstocking of our forests with even more cows to the financial profit of a handful of individuals while the forests continue being decimated by native species.