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Montana Field Guide

Montana Field Guides

Glacier and Ice Field

Provisional State Rank: S2
(see reason below)

External Links

State Rank Reason
In Montana, climate change, especially during the past 50 years, has resulted in rapid shrinking or elimination of more than half the glaciers in Glacier National Park. At current rates of change, the remaining glaciers are expected to be gone by 2030 or sooner.

General Description
This once-widespread ecological system is 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 cover.

Similar Systems

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.

Ecological System Distribution
Approximately 41 square kilometers are classified as Glacier and Ice Field in the 2017 Montana Land Cover layers.  Grid on map is based on USGS 7.5 minute quadrangle map boundaries.

Montana Counties of Occurrence
Beaverhead, Carbon, Deer Lodge, Flathead, Glacier, Granite, Lewis and Clark, Madison, Missoula, Park, Ravalli, Stillwater, Sweet Grass

Spatial Pattern
Large patch

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.

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.

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 Ecological System
  • Details on Creation and Suggested Uses and Limitations
    How Associations Were Made
    We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. 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, Foresman 2012, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system 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, and species that only migrate through Montana were only evaluated for migratory habitat use.  In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.  However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.  The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.  If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.

    Suggested Uses and Limitations
    Species associations with ecological systems 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 (this information can be requested at: or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.  Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.  Land cover mapping accuracy is particularly problematic when the systems 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 ecological system within its known geographic range, portions of that ecological system 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.
    • 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.
    • 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.

Original Concept Authors
NatureServe Western Ecology Team, mod. M.S. Reid

Montana Version Authors
L.K. Vance, T.A. Luna

Version Date

  • Classification and Map Identifiers

    Cowardin Wetland Classification: Not applicable

    NatureServe Identifiers:
    Element Global ID 28570
    System Code CES100.728, North American Glacier and Ice Field

    3130: North American Glacier and Ice Field

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Coulling, P. P., and T. J. Rawinski. 1999. Classification of vegetation and ecological land units of the Piney River and Mt. Pleasant area, Pedlar Ranger District, George Washington and Jefferson National Forests, Virginia. Natural Heritage Technical Report 99-03, Virginia Department of Conservation and Recreation, Division of Natural Heritage, Richmond.
    • Hall, M. H. P., and D. B. Fagre. 2003. Modeled climate-induced glacier change in Glacier National Park, 1850-2100. BioScience 53:131-140.
    • Meidinger, D., and J. Pojar (eds). 1991. Ecosystems of British Columbia. British Columbia Ministry of Forests Special Report Series No. 6. 342 p.

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Citation for data on this website:
Glacier and Ice Field — North American Glacier and Ice Field.  Montana Field Guide.  Retrieved on , from