UC Davis scientist says modern data shows riparian grazing can be sustained

Casper – “We can’t use data from 20 years ago to justify actions taken today,” noted Ken Tate, University of California-Davis rangeland watershed specialist. 

Tate spoke about to grazing riparian areas at the inaugural Wyoming Association of Conservation Districts Watershed Conference held in Casper Feb. 20-21.  

“There are a lot of different opinions for grazing riparian areas,” Tate said. “These differing opinions have wild variations ranging from the riparian areas needing the cow, to the cow single-handedly destroying the ecosystem.” 

He explained decisions are often made using best available science, but best available science isn’t always black and white. 

“When we start using science as a weapon to support a specific paradigm, it becomes a problem,” Tate said. 

He explained seemingly minor differences in studies can produce different results and ultimately support different ideas. 

For example, Tate looked at two studies – one for and the other against riparian grazing, noting researchers utilized different grazing tolerances, which had an effect on the overall outcome of the study. 

Poor management  

“Unmanaged riparian grazing can wreak havoc on riparian systems,” Tate explained. “But we have to keep in mind, less than 20 years ago, proper management was an afterthought, and that affected these areas in a negative way.” 

He explained unchecked grazing reduces the vigor of native riparian plants as whole.

“Chronic, heavy defoliation can reduce primary productivity, root mass and plant vigor,” Tate said. “Competition can shift species composition from high to lower root mass species. This is problematic because these areas depend on deeply rooted plants to prevent damage to the soil and bed.”

He noted the physical stress of cattle being present is also a major factor in unmanaged grazing scenarios. 

“Chronic, heavy livestock hoof trampling can break-down and damage stream banks and damage plant systems,” Tate said.

He also explained these systems possess a hydrologic function threshold, and once it’s crossed, there is catastrophic loss of ecosystem services, saying, “When vertical or lateral erosion occurs, the water table is lowered, which reduces habitat and production.” 

“The implications of this loss of service include unstable stream banks, stream channel erosion, loss of water table and overall decline in water quality,” he stated.

Sustainable management

Though many of the bodies of research between the 1970s and 1990s showed negative outcomes with riparian grazing, modern research accounts for improved management of these areas. 

Tate stated, “A contemporary body of research demonstrates the effectiveness of modern management for achieving multiple ecosystem services.”

He cited studies including a 2013 study showing cattle grazing, water quality and recreation can be compatible goals. Another study conducted in 2013 showed no benefit to the Yosemite toad with livestock removed. 

Tate explained how, prior to 2000, there were no annual use guidelines in place in regards to riparian grazing. Since then, numerous standards have been put in place to ensure the health of these ecosystems. 

“The Forest Service lays out standards for herbaceous vegetation use, stubble height, right to browse on woody plants and stream bank disturbances,” he said.

He explained the key findings of modern research show grazing practices are significantly correlated to riparian health, but the correlation is strongest in meadow systems where stability is most dependent on the health of vegetation.

“There are positive correlations between the health of riparian areas and number of off-stream attractants, herding to control time spent in the area and rest period duration,” Tate said. “There were negative correlations between riparian health and grazing durations, cattle density and frequency of grazing.”

Management

“Front side management prevents catastrophes,” said Tate.

“As a manager, when we view riparian goals and limits, we have to make sure to be location specific,” said Tate. “Often, we get too caught up in the numbers and miss the big picture, we have to look past the numbers to reach overarching goals.”

“As a whole, it shows when managers are putting effort into conservation and good practices,” he noted. “It takes time and effort to move cattle around, build fences and put out attractants such as water troughs and minerals. But these efforts show in the long-run for riparian health.”

“The main thing for managers to remember is clipping or grazing plants can cause damage if left unchecked. Streams rely on healthy plant roots to prevent erosion,” Tate said. “We have to leave enough of the plant for it to function properly and serve its purpose to the environment.” 

Callie Hanson is the assistant editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.