POCATELLO, Idaho — Federal land managers once encouraged western farmers and ranchers to plant Russian olive trees in dry and rocky soils for wildlife benefits and erosion control.
Nowadays, the exotic tree is considered a noxious weed in Montana and Wyoming, and the USDA’s Natural Resources Conservation Service is partnering with southeast Idaho ranchers to remove Russian olives to improve range quality.
Colden Baxter, a stream ecologist at Idaho State University, believes his recent research findings regarding how the species adversely impacts waterways provides further evidence that Russian olives may be doing more harm than good.
“It was chosen by agencies because it grows so well in arid regions,” Baxter said. “It has since escaped those intentional plantings and spread and become by some accounts among the top two or three most abundant woody plants along streams in the West.”
In states in which Russian olive is considered a weed, Baxter said officials worry that the tree is taking over riparian areas and outcompeting native willows and cottonwoods, which support a much broader diversity of wildlife.
Baxter, who has been researching Russian olives for eight years, has found microbes associated with the tree fix nitrogen, which can pollute nearby streams. Elevated nitrogen levels may increase algae growth and choke out dissolved oxygen, and create water-quality problems in reservoirs when combined with olives and leaves that are slow to decompose.
Baxter also hypothesizes Russian olives have supported increased populations of invasive carp, which thrive on the olives. He’s seen a 20-fold increase in carp density compared with estimates from the early 1970s in one stream he’s studied, in which the primary change has been Russian olive numbers. He’s now collaborating with the U.S. Forest Service on a small-scale experimental removal of Russian olives to measure the response by carp.
“Before we do lots of really massive-scale removals, some studies like this might be good to try and evaluate what is to be gained by such efforts,” Baxter said.
The Bureau of Land Management makes a practice of removing Russian olive from public grazing allotments in southwest Idaho in conjunction with efforts to eliminate tamarisk, an invasive plant that’s on Idaho’s noxious weeds list, said BLM fuels specialist Steve Jirik.
Boyd Bradford, NRCS district conservationist in Preston, Idaho, said his office has led a project to remove Russian olives from range land along the Bear River. Ranchers may receive up to $380.43 per acre for cutting, chemically treating and burning Russian olive stands. Ranchers willing to replant native willows and cottonwoods tend to score better for obtaining funding, Bradford said.
Bradford said a single applicant has applied this season for Russian olive removal, now funded through the Environmental Quality Incentives Program. Work is ongoing for five applicants whose removal projects were funded last season through a defunct farm bill program, and three applications were approved during 2012.
Bradford said Russian olives were promoted as good for wildlife and erosion control several years ago, and wildlife concerns are also driving current efforts to remove the species.