Part 15

Beaver Ponds

Fully 10 percent of all the present meadow area in the Rocky Mountains is estimated to have been created by beaver, the only animal besides man that engineers extensive changes in the environment to suit its own needs.

When beavers dam a stream, they set in motion another form of succession. If the resulting backwater floods a forest area, the trees are soon killed, creating a broad opening in the forest canopy. Water-associated plants and shrubs quickly invade the pond and shoreline, creating favorable habitat for waterfowl, moose, blackbirds, amphibians, wading birds, warblers, marsh hawks, and a score of other animals.

After many years the water becomes shallow, filling in with silt and plant debris. When the beavers abandon the site, the dam may rupture for lack of maintenance and the pond will rapidly drain. Or it may continue to hold, delaying for several more years its slow conversion to meadow. Stimulated by the nutrient-rich mud, the water grasses, sedges, and shrubs finally choke the water with their accumulating debris, transforming the area into a bog.

Gradually the ground firms as more humus is created and more silt is trapped. The area becomes meadow, supporting grasses, sedges, and other flowering plants. Trees begin to reinvade the drier ground, and eventually the meadow reverts to forest. Centuries may be required to see this cycle through, from forest to pond, to bog, to meadow, to forest again. At each stage many of the animal inhabitants change: the song of the western robin and the chatter of a red squirrel in the original, pre-beaver forest give way to the croak of a heron; the heron is replaced by the insect-and-berry-eating cedar waxwing; the waxwing is followed by the tree-dwelling western robin and red squirrel.

Lakes Cold and Deep

Seeming to skate on its own reflection, a spotted sandpiper comes in low over the quiet water, wingtips almost touching the surface of the lake. It alights at the shore and folds its wings. Amid the rounded rocks, this plain but elegant little shorebird is all but swallowed up. Teetering constantly on long legs, it sets off along the water’s edge, pecking here and there, coming closer and closer, never forgetting to stop and curtsy, as if acknowledging, while hurrying offstage, the applause of an audience.

As it draws near, several water striders skate away from the shore. A stonefly, scuttling between two rocks, is deftly speared. So large a morsel makes the bird pause and rough its feathers, then scamper into the water to take a drink. Teetering again, it passes in front of me and continues down the shore, where I soon lose sight of it rounding a rocky point.

I am sitting at the foot of Lake McDonald, watching the darkness gather over the valley, seeing the last light slide upward to the tips of the distant mountains. As daylight dissolves, this long fleet of familiar peaks seems almost to glide toward darkness, slow and silent as sailing ships.

The sheet of motionless water stretches many kilometers away between tree-covered moraines. The water is deep and cold. No emergent plants line the barren shore. It would seem that no life, except for the single gull that rests on the water far away, exists in this nearly thousand-meter-high lake.

■ Considering the great volume of Glacier’s large, deep lakes, the life they support is indeed meager. A large part of the reason lies with the nature of their shores, where almost no plants grow. A combination of factors prevents the development of a lush shoreline growth.

Contoured like bathtubs, these steep-sided lakes exhibit narrow or non-existent shoreline shallows, which are vital for the production of rooted plants. Strong wave action and extensive seasonal fluctuations in the level of these natural reservoirs prevent the development of emergent water plants in locations where they might otherwise be expected.

Since sunlight cannot penetrate to the bottom of these deep lakes, they are deprived of bottom-anchored plants in midlake as well. As a result, herbivorous animal life must depend almost wholly on algal growth. Wave action inhibits the spread of free-floating algae by washing much of it onto the shore. Deep lakes are also low in available oxygen, preventing the development of bottom decomposers, which would rapidly release nutrients as they break down the accumulating debris washed into the lake. Without a steady supply of nutrients, plant growth is retarded.

Since the food chain depends upon green plants, the ability of a lake to support higher animals such as fish depends upon its ability first to produce adequate plant growth. The production of one kilo of trout requires that a lake produce about 1,000 kilos of plants to support 100 kilos of herbivorous invertebrates, which are eaten by 10 kilos of carnivorous insects, on which the trout feed.

Compared to smaller shallow lakes, which teem with visible life, cold, deep, nutrient-poor lakes such as McDonald appear to be watery deserts. Yet because of their great volume—Lake McDonald contains 5 or 6 cubic kilometers of water—these large lakes do sustain significant numbers of fish. Of the 22 kinds of fishes found within the park, most are coldwater species. Trout, whitefish, grayling, suckers, minnows, and carp fill the roles of herbivore, carnivore, and scavenger. Agile, highly mobile, and acutely sensitive, fish represent the most successful total adaptation to the aquatic environment.

Through the stocking of nonnative species, including plantings in formerly fish-free lakes, the natural aquatic communities of many of Glacier’s lakes and streams have been permanently modified.

Aquatic food chains are not confined to the water. Ospreys, ducks, mergansers, otter, mink, and many other semi-aquatic or terrestrial birds and mammals utilize the plants and animals of the water. In fall, a remarkable spectacle occurs along the outlet of Lake McDonald. Attracted to the kokanee salmon concentrations, which run from Flathead Lake to spawn and die in these clear, shallow waters, bald eagles collect to exploit the vulnerable fish. In 1977, 444 eagles were counted in one census. This food resource is also exploited by grizzlies, coyotes, skunks, gulls, loons, and other animals. On occasion, even white-tail deer have been observed swallowing salmon!

Shooting Stars

This park is very special. The people who know it well feel proprietary toward its mountains, scattered lakes, and glaciers. Perhaps it is the arrangement of the land, an unsurpassed concentration of American wilderness. Time and again I have thought, as I regarded some aspect of this country, yes, this is exactly right—almost, it would seem, as if some magic existed that could translate thought and emotion into rock and bark.

Glacier remains largely unexploited, bearing still the aspect of the Earth the Indians knew for 500 generations—a land where it is yet possible to feel a sense of discovery, sense that a single man matters. On too many mountains, man has tarnished whatever he has touched; but here the land has shed, as a fir sloughs snow, a long succession of traders, trappers, explorers, hunters, surveyors, prospectors, loggers, settlers, and tourists.

You may walk the same trail a dozen times and not tire of the view. I have given up wondering why. I know only that these are mountains a man might grow old with, and that mountain-fever never diminishes but only changes its look, as a forest does over many years.

Repeatedly I have noticed that this park creates an instant bond between strangers. A certain pause intrudes at the first mention of Glacier National Park, and a look of distance comes, as Red Eagle becomes real again, or the wind at Firebrand is remembered, or the flowers of Fifty-Mountain converge once more upon the senses.

Never are we quenched. If a goshawk rushes past, straining upward with its squirming load of ground squirrel, forever afterward our blood demands more. The sight of a wolverine running is not enough. Nor the magnificent assemblage of bald eagles feasting on November salmon. More days of this: mountain goats leaping impossible ledges, wave tracks from a beaver reaching out on dawn water. There are messages here, loud as kingfishers. The land has languages, stories to tell.

But in wilderness there is no moral, save that it must continue. For all our probings and plottings we discover no adequate interpretation of the forces we find swirling about us. A larch you must touch to know; your neck must feel the ache of too much looking up. Watch its treepoint pirouette. Then, looking back at the world level, you will find that you have lost all answers. We have learned the art of building bridges, cataloging plants, predicting what a shrew might do. Of the essential mystery, we know nothing.

For nature assigns no “roles” to its creatures; there is no “reason” for a forest fire, which burns mightily but with no intent. Life’s only “purpose” is the feeding of life, and the beauty we see therein is but its lack of guarantee: for the chipmunk and the weasel, and the man who measures his life to theirs, no assurance of long days and tempered seasons, abundant seeds, ample meat. In wilderness there is mystery yet, unsimplified, not reduced, resplendent and immense.

Whatever the conclusion of this planet, however many the acts to follow in this consuming drama—mountains coming up, mountains going down, forests, lakes, and seas skimming past like wind-driven scud clouds before a storm—at least in the scant shadow of this present age there is an achievement of sorts. For now, with this creature man, such things as mountains can be loved. And men have memories to fill.

Tomorrow I will look for shooting stars—purple spring flowers that point their fire down, always down toward the center of the Earth, as if to give in their brief term beneath the sun a tribute to this most excellent mystery.

Today I can say nothing more, neck-sore now from looking at larchtops swaying with the wind of this splendid morning.