In the guest column “Bison should be able to roam, not reduced”, the author argues that wildlife does not overgraze, only cows. Further, the author demonstrates an apparent belief in the hypothesis of “Natural Regulation” or intra specific competition. A hypothesis that, an overwhelming amount of documentation, demonstrates is not working in Yellowstone National Park.
The change in plant community composition and production since the “Agricultural Management Era” (during which time wildlife numbers were reduced) ended in 1968 and the Natural Regulation Era began is dramatic. Northern Range production is about 60 percent of what it was in 1963, the time of the last intensive range inventory. Follow-up of YNP Research Biologist Douglas Houston’s work in the early 1970s reflects a major change in plant community composition. Dominant and codominant native grasses have been reduced or eliminated. Recent field work documents production of range plants is less than 25 percent of potential. Well documented research by other scientists indicates the extent of quaking aspen, willow and black cottonwood is less than 10 percent of what it was during the early days of the park. A serious loss of habitat for a diverse community of wildlife. Livestock did not do it! Wildlife did!
The author argues that livestock (cows) severely impact riparian ecosystems, which they can if not properly managed. Livestock have not been present in YNP since the very early time and then in only small numbers and limited locations. He also argued: “Elk, bison and other native ungulates are only concentrated at lower elevations in the park during winter months when plants are dormant. In addition, soils are frozen, so compaction and bank breakage are lessened.” What the author fails to mention is that bison are remaining on low elevation areas in YNP year around. A great deal of what used to be “winter range” is now occupied by bison throughout the year. In addition, not all soils are frozen in winter time. Wetlands and other areas with associated high water tables, such as streambanks are not always frozen. So, there is still potential for impacts by wildlife.
A prime example is Rose Creek which flows across the Lamar Valley and by the Lamar Ranger Station. It is totally devoid of the protective influence of willows. Streambanks are exposed, heavily trampled and sparsely covered with noxious weeds. Bison wallows intersect one another throughout a good portion of the Lamar Valley. So, in effect, the entire valley floor, has been plowed, an unprecedented level of disturbance in any environment, studied by Canadian researchers, who have been documenting historical bison wallow density in different environments along the Rocky Mountains from Alberta to Wyoming. So much for the idea that wildlife grazing of low elevations is benign.
The author creates the impression that wildlife utilizes the Northern Range uniformly. The reality is that, in winter, wildlife utilize the ridge crests, south and west facing slopes most heavily, where the snow blows off or is the thinnest or melts out most quickly. In YNP, those areas represented a significant departure from the potential natural plant community in 1963. Those areas, 43 percent of the Northern Range, are in poorer ecological condition today. How many “sacrifice areas” are acceptable? None
Surely any ecologist, not blinded by his faith in “Natural Regulation” will recognize and understand the implications of too many grazing animals, initially elk and now primarily bison, on the Northern Range. Fundamental to a healthy wildlife population is a healthy range resource.
Clearly, the park cannot support large numbers of bison. Letting them roam as wildlife outside the park has the potential to expand the problem. Most elk management areas in Montana are “over Target”. How can adding bison to the range resource be justified if elk numbers are not being controlled? Obviously, there are other ramifications. Fortunately, Montana has regulations requiring that if bison are to be introduced as wildlife to the plains of Montana, that a determination be made to insure there are adequate range resources to support them.