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Montana Valley and Foothill grasslands

The Montana Valley and Foothill Grasslands ecoregions occupies high valleys and foothill regions in the central Rocky Mountains of Montana and Alberta. The ecoregion occupies the Rocky Mountain Front, the uppermost flatland reaches of the Missouri River drainage, and extends into the Clark Fork-Bitterroot drainage of the Columbia River system.

The Canadian component of this ecoregion is characterized by undulating to rolling topography, and surface deposits are composed of loamy glacial till and clayey lacustrine deposits (ESWG 1995). It should be noted that there are smaller outliers of this region nested within some of the major river valleys (e.g. Bow River Valley) west of the ecoregion that are not shown on the coarse-scaled North American map.

Located in the Chinook belt, this ecoregion is characterized by dry, warm summers and mild winters. Mean annual temperature is 3.5°C, mean summer temperature is 14°C, and mean winter temperature is -8°C. Annual precipitation is approximately 425 mm (ESWG 1995).

  • Scientific Code
    (NA0808)
  • Ecoregion Category
    Nearctic
  • Size
    31,500 square miles
  • Status
    Critical/Endangered
  • Habitats

Description
Biological Distinctiveness
The dominant vegetation type of this ecoregion varies somewhat, but consists mainly of wheatgrass (Agropyron spp.) and fescue (Festuca spp.). Certain valleys, notably the upper Madison, Ruby, and Red Rock drainages of southwestern Montana, are distinguished by extensive sagebrush (Artemisia spp.) communities as well. This is a reflection of semi-arid conditions caused by pronounced rain shadow effects and high elevation. Thus, near the Continental Divide in southwestern Montana, the ecoregion closely resembles the nearby Snake/Columbia shrub steppe.

While other sites may experience similar rain shadow effects, lower elevation, greater overall precipitation, and edaphic variations impede sagebrush growth. Along the Rocky Mountain Front, glaciated potholes in the foothills prairie create extensive wetlands and much more mesic grassland conditions than in the high valleys. The western segments of the ecoregion are within the range of moist airmasses from the Pacific.

In Canada, the grassland community is dominated by rough fescue, with lesser quantities of Parry oat grass, June grass (Koelaria sp.) and wheatgrass (Agropyron spp.). Forbs are also abundant, and include sticky geranium (Geranium viscosissimum), bedstraw (Galium sp.), yellow bean Thermopsis spp.), and wheat grass. Moist sites support shrub communities. Drier sites have an increased amount of needle-and-thread grass (Stipa comata). Trees are found only in very sheltered locations along waterways (ESWG 1995).

Historically, heavy grazing by native herbivores–mainly bison (Bison bison)–was a major influence on most of this ecoregion. Periodic fires were also part of the disturbance regime. Some characteristic wildlife species of the Foothill Grasslands include white-tailed deer (Odocoileus virginianus), pronghorn antelope (Antilocapra americana), coyote (Canis latrans), rabbit (Sylvilagus sp.), and grouse (Dendragapus sp.). The ecoregion supports endemic and relict fisheries: Westslope cutthroat trout (Oncorhynchus lewisi clarki), Yellowstone cutthroat (Oncorhynchus clarki), and fluvial arctic grayling (Thymallus arcticus), a relict species from past glaciation.

The moderating effects of strong chinook winds results in a high diversity of vegetation communities in close proximity to one another. Certain sites contain relatively high levels of species richness. The Centennial Valley of southwestern Montana supports 487 vascular plant taxa (Mahr 1996). This valley supports large breeding populations of trumpeter swans (Cygnus bucinator) and sandhill cranes (Grus canadensis). Owing to its highly productive wetlands and juxtaposition to nearby montane habitats, the Centennial Valley may also be a candidate site for grizzly bear (Ursus arctos) recolonization of grassland habitat. This valley and other undeveloped valleys provide critical linkage habitat for grizzlies and other species moving between separate mountain ranges. Such areas also provide critical seasonal range for ungulates like elk (Cervus elaphus) and bighorn sheep (Ovis canadensis).

Conservation Status

Habitat Loss and Degradation
Approximately 25 percent of the ecoregion remains as intact habitat. Less than 10 percent of the Canadian portion of this ecoregion is estimated to remain as intact habitat. Most of the ecoregion has been heavily altered. Domestic stock grazing, draining of wetlands, and conversion to row crops have been major anthropogenic changes to the ecoregion. Replacement of native species with exotic grasses, and noxious weed invasions, are serious problems.

More recently, development for residential homes has been a major threat to the ecoregion. Most of the tremendous population growth in the Rocky Mountains naturally ends up in this ecoregion, because it is largely privately-owned and lends itself to homebuilding.

Long-term environmental pollution from hard rock mining is a major concern. The ecoregion contains the nation's largest Superfund toxic waste site, stretching along the Clark Fork and Blackfoot Rivers from the Continental Divide west to Missoula, Montana.

Remaining Blocks of Intact Habitat
There are still major tracts of relatively intact habitat in the ecoregion. Along the East Front of the Rockies, from Great Falls to near Calgary, it is possible to find large tracts of grassland that have only experienced grazing. Key areas include:

•the Pine Butte Swamp Reserve, a TNC site near Choteau - southwestern Montana
•extensive wetland areas on the Blackfeet Indian Homeland.
•Whaleback - Alberta
•In the southwestern corner of Montana, there are vast expanses of undeveloped foothills and valley bottoms. In these remote areas, homebuilding is not an immediate large-scale threat, although some key riparian areas are being subdivided and developed.
•The Centennial Valley, the Big Hole Valley, and undeveloped parts of the Madison Valley are relatively pristine sites that are tremendously important to the health of adjacent montane systems.
Degree of Fragmentation
Rapid subdivision in some locales is contributing to wholesale fragmentation of habitat. With subdivision and homebuilding come new beachheads for exotic plant invasions, whether intentional or not. Homebuilding also leads to loss of travel routes and winter range for ungulates and other fauna. This process is most serious in the Paradise Valley, Bitterroot Valley, and the Gallatin Valley around Bozeman. Similar trends may take hold in the Madison Valley in the near future.

Possible oil and gas development on the Rocky Mountain Front in Montana and Alberta could have direct habitat impacts as well as impair connectivity between mountains and grasslands for ungulates, large predators, and other species.

Degree of Protection
The following areas are protected:

•Red Rock Lakes National Wildlife Refuge and Wilderness - southwestern Montana
•Pine Butte Swamp Reserve - southwestern Montana
•National Bison Range - western Montana
•various BLM Wilderness Study Areas in southwestern Montana
•Ross Lake Natural Area - Alberta - 48 km2
Types and Severity of Threats
Conversion of native habitat to homesites is a serious localized threat, although the boom appears to be levelling off. The loss of undeveloped riparian forest linkages across valley bottoms could have serious impacts on the long-term viability of sensitive species like the grizzly bear. Spread of exotic and noxious plant species could be a major long-term threat. Conversion of forest to grazing lands has a major impact on forest species.

Suite of Priority Activities to Enhance Biodiversity Conservation

•Priority sites need to be identified quickly. Three essential components should be protected: 1) rare plant communities/associations (dune communities, fen bogs, wetlands); 2) linkage habitat for large carnivores and other species; and 3) seasonal range for ungulates.
•Any opportunities to encourage or preserve the phenomenon of grizzlies using grassland/wetland habitat should be a high priority as well. These opportunities are present on the Rocky Mountain Front and in the Centennial Valley, in particular.
•Protection for the Whaleback in Alberta.

Conservation Partners
•Alberta Wilderness Association
•Canadian Parks and Wilderness Society, Calgary/ Banff Chapter
•Castle Crown Wilderness Coalition
•Federation of Alberta Naturalists
•Greater Yellowstone Coalition
•The Nature Conservancy of Montana
•The Nature Conservancy,Alberta
•Waterton Natural History Association
•The Wilderness Society
•World Wildlife Fund Canada
Relationship to other classification schemes
The ecoregion boundary closely follows Omernik (1995). Bailey lacks a distinctive counterpart to this ecoregion, since his classification of the same geographic area amalgamates the entire elevational gradient, with the exception of M332C, corresponding the Rocky Mountain Front portion of this ecoregion. This ecoregion follows Küchler's 56 and 57; Küchler classifies the Beaverhead, Red Rock, and Big Hole drainages as 49, distinguishing it markedly from the other Montana valleys.

The Canadian portion of the Montana Valley and Foothill Grasslands is made up of Fescue Grassland (TEC 158) along the face of the Rocky Mountain foothills (Ecological Stratification Working Group 1995). This narrow region is characterized by Grassland, Aspen Grove Boreal Forest (17), and Douglas-fir and Lodgepole Pine Montane forests (5) (Rowe 1972).

Prepared by: S. Primm, R. Usher, K. Kavanagh, M. Sims, G. Mann.

 

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