Writing in Forest and Stream in 1882, George Bird Grinnell described the rapid transformation of the West, and noted, "There is one spot left, a single rock about which the tide will break, and past which it will sweep, leaving it undefiled by the unsightly traces of civilization. Here in this Yellowstone Park the large game of the West may be preserved from extermination…"

In Greater Yellowstone’s natural tapestry, wildlife is a spectacular element, attracting worldwide interest and awe. The Ecosystem is home to the largest herds of elk in North America, and is one of the few remaining areas in the Lower 48 states where the magnificent grizzly bear still roams in significant numbers. Greater Yellowstone serves as wintering ground for the rare trumpeter swan, and is home to the largest free-ranging herd of bison in the Lower 48 states. Greater Yellowstone’s relatively intact natural landscape appears to retain its full complement of vertebrate wildlife. Cougar and wolverine still roam its mountains, bighorn sheep scramble among its cliffs, moose browse its willows, and eagles grace the open sky.

Greater Yellowstone’s tapestry is beautiful because it is diverse, woven of uncountable, individual strands. If a weaver is limited to only a few colors, the figures will be crude, mere outlines, cartoons. If the thread is weak or poorly spun, it may not withstand the years. If the fabric is worn, strained, abraded, the thinnest strands break first. Then the thicker ones part, then the warp and weft disintegrate as the tapestry unravels, until the design is gone. This is a metaphor for life, yet biologists now speak, urgently, of the diversity of life in all of its forms. Richness and variation, it turns out, are not just the surface colors, but the very fiber of Greater Yellowstone’s tapestry of life.

Some wildlife species, such as the elk, are keystone species. They play an indispensable role in basic, natural processes, and their elimination from the Ecosystem would trigger a major change in many other species. Other species, such as the marten, great gray owl and goshawk, represent ecological indicator species, which are closely associated with a particular habitat type that is uncommon and in need of protection. Species like the grizzly bear, bald eagle and ferret and their habitats require protection to prevent their complete loss from the Ecosystem, and in some cases, the planet.