UC forest study: Excluding cattle doesn’t help toad
By Kate Campbell
Fencing out cattle grazed in Yosemite toad habitat areas did not result in improved toad populations, University of California researchers found. Data from a study of preventing cattle from entering toad habitat showed no significant benefits for the species, which is being considered for protection under the federal Endangered Species Act.
Instead, researchers found toad populations varied in size depending on meadow wetness, a function of natural precipitation. Scientists noted different forest activities, such as timber harvest, may actually increase potential habitat for the toad by preventing conifer encroachment into breeding meadows and thereby increasing available water.
The five-year study of Yosemite toad populations and fencing control measures in the Sierra Nevada was published by UC researchers in the November issue of the scientific journal Plos One.
"We basically found the Yosemite toad and cattle use the landscape differently," said Ken Tate, principal investigator and rangeland watershed specialist for UC Cooperative Extension. "The toads use water areas and the cattle use drier meadow areas, which provide better forage."
Researchers studying the possible link between the decline in Yosemite toad populations and cattle grazing said scientists have documented a significant global amphibian decline. Possible reasons for the decline include habitat modifications, disease, invasive species, climate change, pesticides and grazing.
The study, "Determining the Effects of Cattle Grazing Treatments on Yosemite Toads in Montane Meadows," found "no benefit of fencing to Yosemite toad populations." Researchers said their results "do not support previous studies that found a negative impact of grazing on amphibian populations."
Tate said his research team has now published its findings in three peer-reviewed scientific journals. In addition, scientists with the UC Davis Rangeland Watershed Laboratory are finalizing and publishing separate studies on water quality and on meadow conditions in U.S. Forest Service grazing allotments.
The water quality study, which was also published in Plos One, addressed concerns about water quality on public-lands grazing allotments. Researchers called it one of the largest and most comprehensive studies of the impact of cattle grazing on water quality conducted in the West.
In collaboration with the U.S. Forest Service and stakeholders, researchers took more than 700 water samples at 155 sites across 12 grazing allotments. They tested for nutrients and fecal coloforms of E. coli across five national forests in California—Stanislaus, Tahoe, Plumas, Shasta-Trinity and Klamath.
Key findings of the water quality study showed nutrient concentrations throughout the grazing season were "below levels of ecological concern."
"We're in the process now of analyzing meadow plant communities data the Forest Service has collected during the past 10 years, to understand trends in meadow health based on the plants there," Tate said. "Preliminary results show an overall improvement in species richness and diversity, and we're not seeing increases in invasive species."
Tate said the three studies—on the toad and its habitat, the water quality testing and what's happening with vegetation—are "giving us a picture that, with contemporary grazing policies on U.S. Forest Service allotments, conditions are improving and compatibility between livestock production and these other ecosystem services that we need the forests to generate are increasing."
Research suggests standards and practices set in the past several decades by the Forest Service to balance livestock production goals and ecosystem vitality appear to be working, he said.
"Attention by grazing allotment permitees and Forest Service staff to maintain (environmental) standards is largely responsible for improved conditions," Tate said, though he noted that "achieving those standards has come with some cost."
He said during the past 10 years, there has been a 27 percent reduction in animal-unit months in California, meaning there have been increased limits on grazing. Some grazing allotments have been vacated across forests to ensure standards compliance.
"Reopening allotments needs to be reviewed case by case, but it's worth revisiting the need for an allotment to be vacated," Tate said. "It makes sense to take a look and see if it's warranted, based on new grazing strategies that meet both environmental and agricultural goals."
The new research on various aspects of grazing and environmental health in the Sierra Nevada is being widely published in scientific journals. Copies of the studies are at http://rangelandwatersheds.ucdavis.edu/main/projects.htm.
(Kate Campbell is an assistant editor of Ag Alert. She may be contacted at email@example.com.)
Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.