Last phase of Green River project for invasive species was completed

Green River – For the past five years, efforts have been conducted to control the invasive species of Russian olives and tamarisks along the Green River Riparian corridor. 

“We thought if we could systematically approach this issue in a phase type control effort we might be able to succeed in keeping it controlled and at bay,” explains Kevin Spence, Green River habitat biologist for the Wyoming Game and Fish Department.

Invasive species

Russian olives and tamarisks are both introduced species to the Green River corridor, and they have become intrusive by outcompeting the native trees and shrubs in the area. 

In late 2009, a local collaborative working group of local landowners and agency representatives began to address the issue on how to control the invasive species along the lower Green River corridor, specifically in the areas between Fontenelle Dam and the inflow area of Flaming Gorge Reservoir. 

“The biggest thing on the Green River we are trying to do is control, not eradicate, the Russian olives and tamarisk,” comments Spence. “We are looking to control their numbers in a way where they won’t outcompete and overcome the native vegetation like it has in some systems like in the Bighorn River.” 

Phases of project

Teton Science Schools completed the project’s two-phase inventory of the Russian olives and tamarisks locations along the river in 2010 and 2012. 

Phase One was along the riparian corridor between Fontenelle Dam and downstream of Seedskadee National Wildlife Refuge. This area equated to 44 river miles and 28,556 acres. 

Phase Two of the project was completed this January and incorporated the riparian corridor between Seedskadee and Interstate 80 crossing and the Flaming Gorge National Recreation Area of river between Scott’s bottom and Davis Bottom. A total of 28 river miles and 9,000 acres were treated in this phase. 

For Phase Two, the Sweetwater County Weed and Pest District hired Field Services and Weed Control, LLC to perform stump cutting and application of basil bark chemical treatments to control the Russian olives and tamarisks. 

“The larger trees need to be cut down with chainsaws, and their stumps are painted with a chemical immediately afterwards,” says Spence. “Through capillary action, the chemical is drawn into the roots and kills the tree.”  

Wildlife habitat

“Several wildlife species are dependent on sustaining native cottonwoods, willows and riparian shrub habitat along the Green River,” describes Spence. “Preventing this gradual invasion of the Russian olives and tamarisk from becoming a vegetative monoculture along this river will be extremely important for future populations of fish and wildlife.” 

While the seeds from the Russian olives provide a food source for birds and other wildlife, along with shade and windbreaks, the ecological threat to the riparian areas and life stage habitats from the invasive species far outweighs any benefits they could offer. 

“These invasive species are nitrogen fixers,” explains Spence, “which means they can take nitrogen from the air and affect it to the soil and increase nitrogen levels in the soil and water – affecting the water quality next to streams and rivers.” 

The nitrogen fixation and the continuous persistence of the invasive species degrade and potentially can eliminate essential life stage habitats for many terrestrial and aquatic wildlife species. 

Control efforts

Control efforts began along the Green River in 2011 with a combination of stump-cut and chemical treatments to reduce Russian olive and tamarisk along the 4.5 river mile immediately below Fontenelle Dam. 

In 2012, the City of Green River Parks and Recreation Department hired a contractor who performed mechanical removal of the invasive species on 586 acres of riparian habitat along five miles of the Green River. 

In the late fall of 2013 treatment efforts were applied to discourage establishment of re-sprouts and seedlings. 

“We are pretty much done with all the initial treatments, so anything that occurs after this will just be periodic follow-up control efforts,” says Spence. “These efforts are aimed at retreating any kind of re-sprouts or new seedlings that have established.” 

“People who have dealt with this problem before highly recommend to control the growth of these invasive species while there is an opportunity to before they become a huge problem,” relays Spence. “That was the intent of this project.” 

Grant funding

Grant funding was used in 2013 to purchase and plant several 10- to 15-foot Narrowleaf Cottonwood trees and four- to six-foot Silver Buffaloberry shrubs in clusters along the riparian greenbelt where the Russian olive and tamarisk control treatments occurred. 

The species of plants that were planted are native to the area and riparian systems. Taller statured plantings were used to provide some immediate wildlife habitat value and expedite the recovery of the riparian vegetation community. 

The Wyoming Landscape Conservation Initiative, Wyoming Wildlife Natural Resource Trust, Sweetwater County Weed and Pest District, U.S. Fish and Wildlife Service-Wyoming Private Land Partners Program and Seedskadee National Wildlife Refuge provided grant funding and other support for the project.

Other supporters of the project were Teton Science Schools, Wyoming Governor’s Big Game License Coalition and the Wyoming Game and Fish Department.  

Private landowners that are interested in participating in the Russian olive and tamarisk control efforts along the Green River Riparian corridor can contact the Sweetwater County Weed and Pest District at 307-273-9683 or the Wyoming Game and Fish Department Green River Regional Office at 307-875-3223.

Madeline Robinson is the assistant editor of the Wyoming Livestock Roundup and can be reached at madeline@wylr.net.