Glacier and Ice Field
Global Rank:
GNR
State Rank:
S1
(see reason below)
External Links
State Rank Reason
These high elevation snowfields and glaciers have been rapidly melting and shrinking in extent and size and are expected to continue to do so, resulting in their rapid disappearance.
General Description
Land cover composed of unvegetated landscapes of annual/perennial ice and snow at the highest elevations, where snowfall accumulation exceeds melting. The primary ecological processes include snow/ice retention, wind desiccation, and permafrost. Typically, the snowpack/ice field melts for only a few weeks during the growing season. The barren rock and rubble within the glaciers and areas of recent glacial retreat (50 years or less) is part of this system. In Montana, alpine ice-fields are well represented throughout the Northern Rocky Mountains and island mountain ranges. This system is characterized by a very cold climate, high winds and heavy snow accumulation during winter, and a growing season of 60 days or less. Plant cover is low (less than 10%) to non-existent, with exposed, unstable scree, boulders and bedrock constituting the remainder of cover. When vascular plants exist at all, they occur as singular plants among the exposed rocks or in bedrock fractures. These species are typically cushioned, matted or succulent, or grow as flat rosettes, often with thick leaf cuticles or a dense cover of hairs. Algal blooms, insects, and birds or mammals that forage on the insects are generally the only biota. In Montana, climate change, especially during the past 50 years, has resulted in rapid shrinking and elimination of many of the remaining glaciers and most of the permanent snow fields within this system.
Diagnostic Characteristics
Ice fields; glaciers; perennial ice and snow; less than 10% vascular plant cover.
Range
True alpine ice fields occur only in the Northern Rocky Mountains and portions of the Beartooth-Absaroka range. Late-persisting snowfields in the mountains of southwest Montana are more properly classified as Rocky Mountain Alpine Bedrock and Scree or Rocky Mountain Alpine Fell-Field systems, depending on the extent of their vascular plant cover.
Density and Distribution
Based on 2025 land cover layer. Grid on map is based on USGS 7.5 minute quadrangle map boundaries.
Mapped Distribution by County
Beaverhead, Carbon, Deer Lodge, Flathead, Glacier, Granite, Lake, Lewis and Clark, Lincoln, Missoula, Park, Powell, Ravalli, Sanders, Stillwater, Sweet Grass
Based on 2025 land cover layer.
Spatial Pattern
Large patch
Environment
In Montana, this system is well-represented on the higher mountain summits and associated glacial fields and basins below the summits in Glacier National Park. Permanent snowfields are usually found in protected basins and on north and east facing aspects in the Beartooth-Absarokas. Organic matter is usually only found in limited quantities in pockets among boulders, in fractures of exposed bedrock or on the windward leeside of bedrock slabs. This system is characterized by a very cold climate, heavy snow accumulation during winter, high winds, and a growing season of 60 days or less.
Vegetation
Generally, there is little to no vascular plant cover within this system and usually less than 10% cover. Plants colonize in pockets in the fractures of the bedrock or in protected pockets within steep chutes below the summits. Lichen cover is variable, but can be high in some areas. Bedrock that has recently been exposed due to recent glacial retreat is barren.
Dynamic Processes
Glacier and alpine ice fields form when rates of snow accumulation exceed rates of melting. When climate cools and/or snowfall increases dramatically, as it did during the Little Ice Age of 1500-1850, icefields expand and advance. Conversely, when snowmelt exceeds snow accumulation because of warmer and/or drier conditions, ice fields retreat from their terminus and become thinner.
Management
Although off-trail travel and climbing can affect nearby ecological systems, permanent ice fields are generally unaffected by recreation. No special management activities are necessary.
Restoration Considerations
Once lost, alpine ice fields can only be restored by dramatic climate cooling and/or increased snowfalls.
Species Associated with this Community
- How Lists Were Created and Suggested Uses and Limitations
Animal Species Associations
Please note that while all vertebrate species have been systematically associated with vegetation communities, only a handful of invertebrate species have been associated with vegetation communities and invertebrates lists for each vegetation community should be regarded as incomplete. Animal species associations with natural vegetation communities that they regularly breed or overwinter in or migrate through were made by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Werner et al. 2004, Adams 2003, and Foresman 2012);
- Evaluating structural characteristics and distribution of each vegetation community relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each vegetation community;
- Calculating the percentage of observations associated with each vegetation community relative to the percent of Montana covered by each vegetation community to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use. Species that only overwinter in Montana were only evaluated for overwintering habitat use. Species that only migrate through Montana were only evaluated for migratory habitat use. In general, species are listed as associated with a vegetation community if it contains structural characteristics known to be used by the species. However, species are not listed as associated with a vegetation community if we found no support in the literature for the species’ use of structural characteristics of the community even if point observations were associated with it. If you have any questions or comments on animal species associations with vegetation communities, please contact the Montana Natural Heritage Program's Senior Zoologist.
Plant Species Associations
Please note that while diagnostic, dominant, or codominant vascular plant species for a vegetation community have been systematically assigned to those communities and vascular plant Species of Concern were systematically evaluated for their associations with vegetation communities, the majority of Montana’s vascular plant species have not been evaluated for their associations with vegetation communities and no attempt has been made to associate non-vascular plants, fungi, or lichens with vegetation communities. Plant species associations with natural vegetation communities were made in a manner similar to that described above for animals, but with review of Lesica et al. (2022) and specimen collection data from the Consortium of Pacific Northwest Herbaria. If you have any questions or comments on plant species associations with vegetation communities, please contact the Montana Natural Heritage Program's Program Botanist.
Suggested Uses and Limitations
Species associations with vegetation communities should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning. These potential lists of species should not be used in place of documented occurrences of species or predicted habitat suitability models (this information can be requested at: https://mtnhp.mt.gov/requests/), or systematic surveys for species and onsite evaluations of habitat by trained biologists. Users of this information should be aware that the land cover data used to generate species associations is based on satellite imagery from 2016 and was only intended to be used at broader landscape scales. Land cover mapping accuracy is particularly problematic when the vegetation communities occur as small patches or where the land cover types have been altered over the past decade. Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections). Finally, although a species may be associated with a particular vegetation community within its known geographic range, portions of that vegetation community may occur outside of the species' known geographic range.
Literature Cited
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Consortium of Pacific Northwest Herbaria. https://www.pnwherbaria.org/ Last accessed May 30, 2025.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Lesica P., M. Lavin, and P.F. Stickney. 2022. Manual of vascular plants, 2nd Edition. Brit Press. 779 p.
- Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Species of Concern Associated with this Community
Mammals
Birds
- Other Native Species Commonly Associated with this Community
Mammals
Birds
Original Concept Authors
NatureServe Western Ecology Team, mod. M.S. Reid
Montana Version Authors
L.K. Vance, T.A. Luna
Version Date
1/1/2017
References
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