Bighorn Forest plan for weeds, sagebrush sparks battle


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 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 percent of the Bighorn National Forest — some 163,000 acres — according to the draft study. The Bighorn plans to treat about 42 percent — 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 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.

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.

“Forest birds are in decline,” Bighorn Audubon wrote, “with over one billion North American forest birds lost since 1970, and a 30 percent (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.

WyoFile is an independent nonprofit news organization focused on Wyoming people, places and policy.

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