Introduction to Mountain Ecosystems
The mountain world of the North Cascades is a rich and varied ecosystem - a place bound together by geography and climate and by the interactions of living communities of plants and animals. It is the dramatic variations that we notice first: the sharp contrast between old-growth forests of the river valleys and dwarfed and twisted krummholz trees of a subalpine ridge; the difference between the lush greenery of the west side and drier forests of the eastern slope. Not all the differences between habitats are dramatic, however. Subtle changes may be noticed as one habitat and community grade almost imperceptibly into another.
The North Cascades ecosystem contains many different habitats. Ecologists compare an organism's habitat to its "address". Habitat is a combination of the physical environment - the rocks and land and water - as well as all the other organisms that live in the same place. Together these plants and animals make up an interacting, interdependent community. These habitats range from the microhabitat of the forest floor, a world of fir needles and decaying wood, home of the centipede and wolf spider, to the trout-filled waters of Berdeen Lake, hidden away in the backcountry and accessible only by days of rugged, cross-country travel. The mountain forests support communities of plants and animals different from those of the river valleys. Plants that flourish in subalpine meadows are strangers to the more severe conditions of alpine ridges.
As we hike up the river valley toward the montane forest, the plants and animals change around us. The giant ponderosa pines of the lowlands give way to Douglas-fir and Pacific silver fir. The merganser and harlequin ducks of the lower river make way for dippers and spotted sandpipers. As we leave the river behind and climb higher, we enter the subalpine world of meadows and stunted krummholz trees. At the pass, gateway to the peaks beyond, we find ourselves in a different land filled with different creatures - a world apart from the valley still shrouded in mist far, far below.
Small cushion plants dominate the high meadows with their low growing, prostrate masses of green and brightly colored flowers. Climbing higher, toward the glacial snows, we enter a world of rock and ice. Along the rocky summit ridge of the peak, the only living things we find are lichens, a few insects, and two rosy finches, squeaking as they hop on the topmost crags, oblivious to the precipice below.
Over millions of years of geologic time, living things adapt to their environment. Every species finds a unique place in its habitat and community. Life is limited by the physical environment (temperature, wind, moisture, space, and length of growing season) and by other organisms (competition and predation). An organism must be able to cope with all of these to survive.
Few untrammeled wilderness areas remain in the world today; the Pacific Northwest mountains still contain some of those. Many habitats and natural communities have been preserved in as pristine a state as possible in national park or forest wilderness areas. These communities exist now as they have existed for thousands of years. They are living preserves where we can experience the natural world untainted by any direct impacts of industrialized civilization. Unfortunately, indirect effects like acid rain and smog reach and change wilderness areas that are home to many organisms and communities that can exist only in a truly wild state. Further, human presence drives away many species, including the grizzly and the wolf, in search of undisturbed terrain. By learning about and respecting our remaining wilderness areas, we can safeguard those species reliant on them for survival.