A Dec. 30 Missoulian guest column contended that bison herds in Yellowstone needed to be reduced because of alleged overgrazing. Implicitly the authors were condoning the continued slaughter of Yellowstone’s genetically unique wild bison to “save” Yellowstone.
The debate about native wildlife grazing influences in Yellowstone, particularly elk, and the “need” for artificial reduction (termed management) has been argued for decades, particularly by those trained in livestock management. The traditional range management approach ignores many unique factors about wild ungulates and their influence on the landscape.
Domestic livestock are concentrated on public lands in the summer months when plants are actively growing. The negative consequences of livestock grazing are well documented and include reduction in seed production, loss of vigor and selective removal of perennial plants.
Damage to riparian areas by bank breakage and soil compaction, social displacement of native ungulates like elk as well as the forage competition with native wildlife from butterflies to elk are also other livestock-induced impacts.
By contrast, overall wildlife numbers are much lower than domestic livestock and are widely distributed during the summer, reducing ecological impacts.
Elk, bison and other native ungulates are only concentrated at lower elevations in the winter months, when plants are dormant. In addition, soils are frozen, so compaction and bank breakage are lessened, all of which helps to reduce the browsing/grazing impacts associated with native wildlife.
Though park willow and aspen were often hedged (short), they persisted despite heavy browsing pressure because they could put out leaves in the summer months and grow without significant browse pressure, maintaining seed and energy production. Interpreting bison and elk influences without considering seasonality of use is a mistake.
There is another temporal aspect to the entire debate of wildlife numbers as well. Wildlife populations fluctuate over decades in response to long-term climatic conditions, predators and other influences.
The presence of wolves, combined with other factors like changing migration patterns, drought, harsh winters and wildfires, has led to an overall reduction in elk influence on plant communities.
For decades, I have hiked weeks at a time in Yellowstone’s backcountry, leading trips as a commercial guide, as well as for my own enjoyment. Even during the 1980s and 1990s, when many asserted there were “too many” elk in Yellowstone, I could go days and sometimes a week or more in the backcountry without seeing more than a few elk at a time and an occasional small herd.
Nearly all early references to wildlife in the Yellowstone region by trappers, miners and military expeditions were recorded in the summer months when wildlife is widely distributed. Even on the Great Plains, wildlife was patchy in distribution, and expeditions could go weeks and months without seeing a single bison herd.
When the Lewis and Clark expedition traveled up the Missouri River in Montana in 1804, they noted an abundance of bison. Yet, on their return trek, the Corps of Discovery split at Lolo, Montana. William Clark traveled hundreds of miles in bison habitat, including down the Upper Missouri tributaries to Three Forks, through the Gallatin Valley where Bozeman is located, over Trail Creek by Livingston, and down the Yellowstone River nearly to the present-day Billings area before he encountered a bison herd.
There is no logical reason why bison and elk would not migrate up into the mountains to take advantage of nutritious summer forage. Bison remains have been recorded in many mountain locations, including at elevations of over 10,000 feet in Colorado and elsewhere. However, in winter, they would move to lower elevations.
The major problem for Yellowstone’s bison is that the traditional migration routes are blocked by hunters and Department of Livestock agents who corral bison for slaughter.
If there are too many bison for the northern range, it is an entirely artificial problem created by the livestock industry. Until we free up bison to move to other public lands outside of the park, one cannot assert that reductions are necessary.