By Renae Counter Explorebigsky.com Editorial Assistant

BIG SKY – Noxious weeds have invaded the winter range for the big horn sheep living near Big Sky. Known as the Spanish Peaks Big Horn Sheep Herd, approximately 150 of the animals spend winters in the lower elevation areas between Moose Creek and the corner of Highway 191 and Lone Mountain Trail.

Noxious weeds are nonnative, invasive plant species that cause harm to an ecosystem by overpopulating and destroying native plant life. Weeds including spotted knapweed, hoary alyssum, houndstongue, oxeye daisy, Canada thistle, chet grass and musk thistle have populated these hundreds of acres near Big Sky, causing damage not only to the land but the wildlife as well, said Jennifer Molher, coordinator of the Gallatin/Big Sky Noxious weed committee.

Once noxious weeds find their way into an area, it’s quick and easy from them to reproduce and travel. One prime example is houndstounge, which is identified most easily by its sticky seeds called spurs. These attach to big horn sheep and other wildlife, which then transport them. Hikers, motor vehicles and natural elements like wind are also modes of noxious weed transportation.

Molher has worked in collaboration with the Gallatin County Weed District, the Gallatin National Forest Service, the Montana Department of Transportation, and Montana Fish, Wildlife and Parks to reclaim the area, one weed at a time.

The group began spraying the herbicides Forefront R&P and Telar along with pulling noxious weeds last year, with the project continuing into 2012. For two days in late June, crews of 12 – 14 volunteers climbed the steep slopes along Highway 191 and Lone Mountain Trail, equipped with 37-pound plastic backpacks full of spray, and began taking down the weeds.

The idea is that with repeated efforts, the weeds will be reduced or eliminated, and native vegetation will again begin to flourish. This, Molher says, will benefit sheep and also other wildlife.

“A healthy winter ranger equals healthy sheep,” Molher said.

Four elements are crucial for a healthy sheep population: plentiful wild grasses and shrubs, reliable water sources, a wide range of view to see predators, and bare slopes to escape danger. Noxious weeds threaten have taken hold on much of the area though, pushing out native vegetation. The ensuing soil erosion causes slope corrosion, which in turn can find its way into nearby creeks and rivers as a pollutant, Molher said.

Opponents of such treatments point out that the spray used to kill the weeds is toxic itself, and remains in the ecosystem for many years.

“We tend to spray as a gut reaction and not think about the level of disturbance it is causing,” said Matt Lavin, a professor of Plant Biology at MSU.

Noxious weed sprays will kill broad leaf plants, meaning native wildflowers also die as a result of spraying. The group replaces the dead plant life with something that will thrive such as native grasses.

The noxious weed committee tries to use the smallest amount of chemicals possible, but Molher says they’re necessary at times.

Julie Cunningham, a biologist for Fish, Wildlife and Parks, has been studying the herd since 2009 and has records dating back to 1980. With a population of approximately 150 this year, the herd is stable, she says. It could support a gain or loss of 20 percent and still be healthy, but any more than that would make the population unstable, she said.

“When conditions get really hard, fewer sheep will be able to make a living.”

Because big horn sheep are on the U.S. Forest Service’s “sensitive species” list, the Gallatin National Forest manages the animals carefully to ensure their conservation.

“Noxious weeds don’t obey fence lines,” Mohler says, meaning that because they’re on private land as well as public in the winter range, it will take collaboration to reclaim and maintain a healthy habitat.

Molher urges private landowners to control and maintain noxious weeds that may have spread onto their land. Effective weed management can be made with proper treatment over a certain course of time, depending on the amount of noxious weeds and how long they have inhabited the land.

“More people treating noxious weeds creates more pressure to protect the environment,” Molher said. “Landowners begin to realize that if they don’t take care of their land it affects the wildlife.”

Gallatin/Big Sky Noxious Weed Committee works under the Big Sky Natural Resource Council which receives funding from the Big Sky Resort Tax. This year BSNRC received $19,000 in resort tax funding for weed control projects. From that, $225 was allocated for this project to cover supplies for the crew.

Gallatin/Big Sky Noxious Weed Committee conducts free landowner visits as well as offers a cost share program to help with effective treatment of noxious weeds. Visit bigskyweeds.org for more information.