Glacier National Park (NP) encompasses several different ecosystems (e.g., westslope forest, eastslope forest-bunchgrass, alpine, aquatic [McClelland ca. 1970]).

Glacier National Park is one part of an ecosystem which is roughly seven to ten times the size of the park alone (Salwasser et al. 1987:169, Hayden 1989:12).

Glacier National Park is one part of the ecosystem that is the entire planet's interacting biosphere, lithosphere, hydrosphere, and atmosphere.

While each of these statements is valid and offers an interesting perspective for interpretation, the second one is perhaps the most useful and certainly the most thought-provoking to scientists, resource managers, and residents concerned with natural resource conservation and use in the region surrounding and encompassing Glacier National Park.

As is true of almost any protected area in the world, political boundaries in this region have little to do with ecological realities (Newmark 1985). The plants and animals in Glacier move freely (for the most part) across park boundaries onto adjacent public and private lands and back again. Furthermore, Glacier is probably not big enough by itself to support viable populations of many of its resident species, particularly large or predatory animals like wolves, grizzly bears, and mountain lions (see Information Paper 5). And, perhaps most importantly, human activities on one side of the park boundary can have critical consequences both for people and for the rest of the biota on the other side.

If we want to conserve the biological diversity and maintain the naturally functioning ecosystem upon which people's lives and livelihoods in this region depend, it therefore makes sense to consider the region as a single ecological unit, as defined in statement 2 above. This ecosystem has been variously referred to as the Northern Continental Divide Ecosystem (NCDE) (e.g., Salwasser et al. 1987), the Crown of the Continent Ecosystem (Hayden 1989), the Northern Rockies, and the Backbone of the World (Wagner 1989). NCDE is the name that has been most commonly used in scientific literature, but it disregards the fact that a substantial portion of the Continental Divide lies to the north in Canada, and that a portion of the ecosystem itself belongs to the southernmost part of the Canadian Rockies. In these papers the name Crown of the Continent Ecosystem (CCE) will be preferred. (The term Crown of the Continent is derived from the title of an article written by George Bird Grinnell [1901] describing his travels in this region.)

The CCE includes the mountainous regions of northwestern Montana, southwestern Alberta, and southeastern British Columbia. At the core of the ecosystem lie Waterton Lakes and Glacier National Parks, the Bob Marshall-Great Bear-Scapegoat Wilderness complex managed by the U.S. Forest Service, and adjacent areas (see Information Paper 2). The ecosystem encompasses the headwaters of three of North America's major river systems: the Missouri/Mississippi, the Columbia, and the Saskatchewan/Nelson. It is characterized by similar topography and ecological communities (see below), and it contains enough habitat to support viable populations of most resident plants and animals.

Different ecosystem components have different boundaries (e.g., grizzly bear range versus moose range) (Agee & Johnson 1989) and different ecosystem processes operate over different spatial and temporal scales (e.g., fire versus soil formation). If the CCE's borders were drawn to incorporate the habitats needed to support viable populations of all native species and to include the entire area over which inputs and outputs enter and leave the ecosystem, we would be approaching the ecosystem definition in statement 3 above Glacier as part of the entire earth's ecosystem. Migratory birds that spend part of the year in Glacier, for example, may depend during part of the year on habitats as far north as the Arctic Circle and as far south as Central America. Furthermore, as a result of human technologies and global atmospheric patterns, activities on the other side of the globe as well as activities only a few miles away may impact plants and animals locally (e.g., the release of airborne pollutants or radioactive materials).

Including an entire continent or an entire planet in day-to-day ecosystem research and management efforts is obviously infeasible. But neither can far-away events destruction of habitats of migratory or wide-ranging species, dispersal of pollutants from sources hundreds or thousands of miles distant, and so forth be ignored by ecosystem managers. Rather than attempting to delineate precise ecosystem boundaries, therefore, the CCE's boundaries beyond the core area should be considered flexible, to be defined according to the question, issue, or study topic at hand (see Theberge 1989).

What lives in the CCE?
Compared to a tropical rain forest, in which a single acre may contain as many as 200 different kinds of trees with thousands of associated invertebrates and other species, temperate ecosystems are relatively impoverished in biological diversity. But within the temperate zone, the CCE stands out as a rich repository of diversity at all levels of biological organization, from genes and species to habitats and communities. (See OTA 1987:37-43, Norse et al. 1986:2-6, and NH 2.6, 3.3, and 4.13 for discussions of the different levels of biological diversity.) The description below of the species, genetic, and community diversity in the CCE draws mainly on data for Glacier National Park alone; similar summary data for the entire CCE has not been compiled. However, Glacier has probably been the most extensively studied part of the ecosystem, and contains a fairly representative portion of the range of biological diversity found across the entire CCE.

Species diversity. Species e.g., Columbian ground squirrels (Spermophilus columbianus), glacier lilies (Erythronium grandiflorum), western larch (Larix occidentalis), or mosquitos (Aedes communis) are the elements of biological diversity that we most readily recognize and identify with. Not surprisingly, however, most of us find it easier to identify with some species (large mammals, birds, trees) than with others (bugs, slugs, and molds, for example), and it is the chosen few belonging to the former group that receive the bulk of our attention.

While we can be confident that all or most of Glacier's resident bird and mammal species have been recorded, any study of an invertebrate group in Glacier is likely to turn up several previously unknown species. For example, Debinski (1991) recently found four butterfly species in Glacier which had never been recorded in the park and butterflies are probably the most studied of insect groups worldwide. When you consider that every mammal or bird in the park is likely the host of several parasitic or mutualist invertebrate species, it becomes obvious that the number of invertebrate animals in Glacier including all the butterflies, moths, snails, slugs, ants, fleas, wasps, bees, centipedes, springtails, mayflies, dragonflies, termites, ticks, mites, spiders, worms, flatworms, roundworms, rotifers, and so forth undoubtedly dwarfs by an order of magnitude or more the number of all other animal taxa combined. (Martens [Martes americana], for example, have been reported to host 13 or more species of fleas, several worms, at least one tick and one mite species, and a variety of other microorganisms [Clark et al. 1987].)

Note that while many people use the term "wildlife" to refer to all the animals of a region, to most people the term conjures up only large mammals, or only mammals and birds or even, for some people, only game species like elk. Usage of the term may unwittingly contribute to a general unmindfulness of the abundance and ecological importance of insects and other invertebrates. (See Ehrlich & Ehrlich 1981 and Information Paper 3 for discussion of the values of insects.)

Genetic diversity. Genetic diversity is the variety of genes within and between populations or organisms. For example, in any given human population, each person has a distinct set of genes (genotype) that is reflected by his or her unique combination of hair, skin, and eye colors, blood

type, and other genetically determined characteristics. When two human populations are compared say, one in the U.S. and one in India between-population genetic diversity can be seen in the different frequencies of genes coding for traits like skin color, hair color, and resistance or susceptibility to certain diseases. Genetic diversity may be quantified by measuring observable, genetically determined characteristics (phenotypes) or by gel electrophoresis, a sophisticated laboratory technique that involves directly measuring the proteins produced by genes.

The species diversity of the CCE obviously is underlain by a wealth of genetic diversity, but little of it has been quantified. A notable exception is the extensive genetic research that has been conducted on westslope cutthroat trout in Glacier, which have been found to be remarkably genetically pure in spite of the presence of introduced species with which, under certain circumstances, cutthroat sometimes hybridize (see Information Paper 5). Studies are also underway to examine the genetic diversity of certain plant species in the park (see Information Paper 6).

Community and landscape diversity. Higher-order patterns of diversity (above the species level) are the most difficult to describe and quantify, yet they generate much of the aesthetic value we find in natural landscapes they create the scenery that attracts people to places like Glacier National Park. Higher-order patterns are described as habitat, community, landscape, or ecosystem diversity. Each refers to the variety of arrangements and contexts in which living things associate over space and time (see Information Paper 4).

For example, elements of community diversity in an area might include a meadow, a riparian (streamside) community, and one or more different types of forest. (Note that, as with taxonomic groups or ecosystems, the community boundaries and classifications we choose are somewhat arbitrary since nature exists on a continuum. This is especially true of systems used to classify community types, since no two places on earth have the exact same assemblage of plant and animal populations mixed in the exact same proportions.) Elements of habitat diversity for a particular species, like the grizzly bear, might include alpine meadows, avalanche chutes, and huckleberry patches. The term landscape diversity is often used to express not only the different community types in an area, but also their distribution relative to each other and to human-made elements like roads, farms, and so forth (Forman & Godron 1986). For example, an area may contain only two community types, say a forest and a meadow, but there may be five times as much of one as the other; they may be arranged in an elaborate mosaic of small patches or in two large blocks; they may be bisected by roads or bordered by shopping malls.

Climate and soils are the main factors which determine the climax community of any given area. (A climax community is a more or less stable assemblage of plants and animals that is characteristic of an area; see Norse et al. 1986.) The Crown of the Continent Ecosystem is particularly rich in community diversity because of the contrast in climates between the east and west sides of the Continental Divide, the large amount of topographic relief, and the presence of both calcareous (calcium-rich, derived from limestone) and non-calcareous soils (Lesica 1985, Edwards 1957, McClelland ca. 1970). Species from five major floristic provinces meet in Glacier NP: the predominant Northern Rocky Mountain flora; Great Plains flora on the eastern margins of the park; Pacific northwest and boreal flora which reach their eastern and southern limits respectively in the park; and, above treelimit, many Arctic-alpine plants (Lesica 1985).

Specific climax communities in Glacier can be identified within four broad ecosystem types in the park: westslope forest, eastslope forest-bunchgrass, alpine, and aquatic ecosystems (McClelland ca. 1970). On the west slope of the continental divide climax communities include spruce/subalpine fir, cedar/hemlock, and Douglas fir forests, with ponderosa pine and bunchgrass prairie remnants on river benches in the northwest. On the east slope spruce/subalpine fir and Douglas fir forests and bunchgrass prairie are the climax communities. Above treeline in relatively flat, stable areas, alpine meadows are the climax community. And each of the three major river systems (Missouri, Columbia, and Saskatchewan) has a distinct aquatic community. Each of these terrestrial and aquatic communities has associated with it a characteristic component of animal species (McClelland ca. 1970).

Natural disturbance undoubtedly contributes to and greatly increases both community and landscape heterogeneity in the CCE as it does in other ecosystems (see Romme 1982, for example). Fire is the most important disturbance in the region, but other commonly occurring disturbances include avalanches, landslides, treefall, windstorms, floods, and epidemics such as bark beetle infestations. These disturbances interrupt the process of succession toward climax communities, setting them back to earlier successional stages known as seral community types (see Norse et al. 1986:14-19). Seral communities on the west side of the park include extensive lodgepole pine and western larch stands maintained by fire, and shrubby vegetation created as a result both of fire and of avalanches. On the east side fire may be responsible for maintaining both lodgepole pine and aspen stands, and avalanche-maintained seral types are frequent as well. In the alpine zone, rocky outcrops and talus slopes support seral alpine fellfields, and some alpine meadows that appear to be climax communities may in fact partially owe their existence to fires which prevent forest encroachment (McClelland ca. 1970).

Taking the long view of the CCE
As a result of short-term natural disturbances and long-term shifts in environmental conditions (e.g., glaciation, climate change, mountain building, soil formation, and even continental drift), the biological diversity of the CCE has constantly changed over time, and undoubtedly will continue to change in the future (see Brubaker 1988, Information Paper 7). Recognizing this dynamic nature of ecosystems is critical to preserving natural ecosystems (Christensen 1988). Even if we wanted to maintain static "vignettes of primitive America" in our parks (see NPCA 1989), we would probably be unable to do so over the long term (Brubaker 1988), and in the short term we would be wasting valuable resources in fighting a losing battle (cf. the Yellowstone fires of 1988, during which $120 million [GYCC 1989] was spent trying to control fires that were uncontrollable and probably inevitable [Romme & Despain 1990]). At the same time, all parks and protected areas have already been modified to some extent by human activities. A major challenge for ecosystem researchers and managers, therefore, will be to distinguish between natural and inevitable changes (including species extinctions and immigrations see Information Papers 4 and 5) and human-caused changes that may be irreversibly diminishing biological diversity and ecosystem health. Inventory and monitoring programs in Glacier (see Information Paper 8) may provide crucial tools for meeting this challenge.

References

Agee, J.K. and D.R. Johnson. 1989. Ecosystem management for national parks. Courier 34(12):6-9.

Myers, J.P., R.I.G. Morrison, P.Z. Antas, B.A. Harrington, T.E. Lovejoy, M. Sallaberry, S.E. Senner, A. Tarak. 1987. Conservation strategy for migratory species. American Scientist 75:19-26.