The ecological interactions of plains bison as large-scale ecosystem engineers are important for the maintenance of grassland and shrub steppe ecosystems. For the past 10,000 years, bison were the dominant herbivore in North America, and their grazing patterns influenced the structure of grass species, mosaics of vegetation, and fire dynamics, which in turn influenced habitat for grassland insects, birds, and small mammals. Bison ‘horning’ and ‘rubbing’ behavior prevented woody species from taking hold in grassy areas and bison wallowing behavior may have created enough depressions in the landscape to create habitat for amphibians. The decimation of bison, gradual domestication and increased husbandry of bison in enclosed spaces has begun the steady process of rendering the bison “ecologically extinct.”
Although bison are demographically secure the current status of bison is problematic and bison today face consistent threats to its long term existence and role as an ecological driver for prairie systems. Most herds are not large enough to sustain long-term genetic integrity. Studies have estimated that the minimum viable population size for a bison herd is 400 animals, and that there is a significant evolutionary advantage to a herd with at least 1,000 individuals. Over 70% of plains bison herds have fewer than 400 animals and there are only two public/conservation herds larger than 1,000. Furthermore, genetic complications exist in that many bison herds exhibit a history of cattle gene introgression. As yet, with current technology, it is still not completely known how many genetically pure bison exist in public or conservation herds. Other threats to the bison‘s long term existence include the lack of available land for large, ecologically functioning herds to roam. Large parcels of land are becoming increasingly rare, meaning that ecologically meaningful bison restoration must occur on multi-jurisdictional landscapes. In addition, the perception of disease threat (particularly brucellosis, a disease transmissible to cattle) limits tolerance for bison on both public (Bureau of Land Management/National Grasslands) and private (near ranches) land, and has led to regulations that severely restrict bison restoration in many places.
Bison ecological restoration will require the establishment of larger, free-ranging herds that interact in ecologically significant ways with native species and systems. To accomplish this, stakeholders will need to overcome several significant obstacles, both scientific and at the policy level. Some of the major obstacles include: 1. Land availability: Large parcels of intact grasslands are becoming increasingly rare, meaning that bison restoration must occur on multi-jurisdictional landscapes. 2. Disease: The perception that bison routinely carry and transmit introduced cattle diseases, and animal disease regulations that severely restrict bison restoration in many places. 3. The public perception of bison not as wildlife but as a form of exotic livestock to be managed behind a fenced pasture. This creates significant obstacles for large scale restoration that enables the ecological role of bison on native grasslands.
Conservation Relevance for the Northern Great Plains:
The extraordinary productivity of the Great Plains has driven land conversion over the past century. The region supplies roughly 25% of the world’s total production of six major food crops. The region also contains one of the continent’s greatest oil and gas reserves and, as a result, is experiencing rapid development. Although facing degradation and fragmentation, the region presents enormous conservation opportunities because it is one of the least densely populated areas in the world and where a few ecologically intact grasslands remain. These last remaining blocks of native grasslands deserve protection. It is critical to maintain important ecological processes operating on these grasslands and to restore keystone species, such as bison, to promote sustainable healthy grasslands that benefit wildlife and humans alike. For these reasons, conservation and restoration of the Great Plains is a critical priority.
For millennia, grassland wildlife specialized on habitats created by large free-ranging grazers. Due to the removal or replacement of native grazers modern land uses have created a vastly different landscape that is fragmented, less diverse, and altered in terms of dynamic ecosystem drivers which once maintained key habitats. Interactions between bison, prairie dogs, human hunters, and fire created a diversity of large-scale habitats that shifted in space and time. Such a shifting mosaic of habitats provided a wider array of habitats than is present now. This change toward a monolithic grassland structure affects the survival and viability of many other species. For example, certain breeding birds like McCown's Longspurs and Mountain Plovers prefer heavily grazed areas while Sprague’s Pipits and Baird's Sparrows favor more lightly grazed grasslands for nesting. Modern grazing management practices that do not mimic historical patterns will dramatically influence which bird species remain viable in the ecosystem. The return of large scale bison grazing could restore the natural heterogeneity needed to sustain the natural diversity of bird species in grasslands.
- Threats identified on NPCN interactive map at https://plainsconservation.org/npcnWebmap/index.html:
- Land Conversion – fragmentation, sodbusting, and pesticide use in grasslands.
- Oil & Gas – fragmentation and industrial development of intact grassland
- Land use practices – the current prevailing grazing regimes and lack of fire threaten the quality and quantity of suitable bison habitat. Fencing for livestock can affect wildlife movement and migration and limit wide ranging bison herds.
- Specific Grazing issues – public grazing allotments and fear of economic impacts.
- Limitations of the current U.S. Farm Bill – incentives for landowners that can be bad or good for grasslands (incentives to grow crops can further reduce grassland extent, while incentives to retain native cover can protect a wide array of grassland plants, animals and ecosystem services). The complexity of the current farm bill and a prevailing conservative policy on ranching and farming make the introduction of a new grazing species to large landscapes incredibly difficult.
- Federal, State and Provincial legislation or policies that change the status of bison, restrict government resource agencies ability to plan, manage and restore American Bison or threaten tribal sovereignty. For example, last year, 2012, 14 pieces of state legislation were introduced into the Montana legislature that would directly or indirectly impact the ecological restoration of bison in that state (on tribal and non-tribal lands). Although these bills were defeated or vetoed by the Governor we can expect future attempts to limit the restoration of bison on public, tribal or private lands.
- Canadian Prairie Farm Rehabilitation Administration (PFRA) lands, similar to U.S. Federal lands abandoned by homesteaders during the Dust Bowl, (in southern Saskatchewan equal 1.6 million acres of native grassland) will no longer be under Federal control and their fate is uncertain. The loss of these habitats represent a permanent loss of future restoration opportunities for American Bison in Canada. See: http://pfrapastureposts.wordpress.com/
- Industrial development for Coal, Oil and Gas production in the Bakken field and along the Rocky Mountain Front in U.S. and Canada. Coal development at large scale is emerging in many areas across the Northern Great Plains and leads to an increased human footprint. The national energy policies in U.S. and Canada are promoting energy development that will forever change the intact nature of grasslands and foothills habitat in the Northern Great Plains.
- Prevailing Public Perceptions – People continue to view bison as extinct relics that are to be viewed but never experienced in grassland ecosystems. Most bison are treated as exotic livestock rather than wildlife creating a management paradigm that includes intensive husbandry. In addition, people view the Great Plains as a working landscape and not in the context of protecting wildness or preserving ecological integrity of Americas grasslands.
- Climate Change – a changing climate will be both a threat and opportunity for bison. For dry areas a warming planet will make them inhabitable for bison which now can range far to the south in near desert environments. Warming may also make some habitats in Canada and in foothills regions more suitable for a grazer such as bison. Bison are Pleistocene relics and adaptable to climate change which may be an advantage over cattle or other livestock.
Collaborate with and support tribes who want to restore bison to their lands or partner with other government agencies to restore bison across multiple jurisdictions.
There are opportunities to partner with private landowners in ecological restoration. The majority of land in the region is privately owned and grazing for cattle production is the dominant use. However, based on prior historical situations and current models we believe bison and cattle can be compatible. We have the opportunity to develop pilot projects to demonstrate coexistence on a shared landscape and innovative business models for economic partnerships among State, Provincial, Federal and private partners in conservation.
Production of Best Management Practices exist or are being developed for:
- Oil & Gas well & road densities
- Agricultural practices – grazing, fencing, water use
- Grassland Restoration – re-seeding, fire, grazing
- BLM Environmental Impact Statement/Resource Management Plan
- National Grasslands Planning
Metrics are being developed to gauge success in grassland restoration and measure the benefits of bison on large landscapes:
- Bison grazing can promote heterogeneity in grassland plant community structure.
- Birds as indicators of ecosystem health and bison ecological restoration – In addition, bison grazing can create suitable habitat for endangered grassland birds.
- Increased understanding of the benefits provided by bison restoration and recovery for other types of endangered wildlife like prairie dogs, sage grouse, and ferrets.
- Other bioengineering influences like wallowing, tree/shrub rubbing and nutrient cycling are exhibited.
- Bison can provide economic benefits to mankind through innovative nature-based businesses that serve local communities.
Political initiatives promote the recovery and restoration of American bison:
- National Bison Legacy Act www.votebison.org
- COSEWIC review of the status of American Bison in Canada
- Department of Interior Bison Initiative and Working Group
Public Education Campaigns are being developed or are underway:
- National Bison Day, November 2, 2013
- American Bison Society Meeting, Sept. 16-19. Media outreach opportunities and mini film festival at Big Sky.
- NGO/tribal sponsored outreach and education-Newsletters, video, and websites.
- Marketing bison as a climate adapted species in a time of changing climate.