Greater Yellowstone Ecosystem - Ecosystem Management By Species

Ecosystem Management By Species

The great ecosystem concept has been most often advanced through concerns over individual species rather than over broader ecological principles. Though 20 or 30 or even 50 years of information on a population may be considered long-term by some, one of the important lessons of Greater Yellowstone management is that even half a century is not long enough to give a full idea of how a species may vary in its occupation of a wild ecosystem.

For example, anecdotal information on grizzly bear abundance dates to the mid-19th century, and administrators have made informal population estimates for more than 70 years. From these sources, ecologists know the species was common in Greater Yellowstone when Europeans arrived and that the population was not isolated before the 1930s, but is now. Researchers do not know if bears were more or less common than now.

A 1959-1970 bear study suggested a grizzly bear population size of about 176, later revised to about 229. Later estimates have ranged as low as 136 and as high as 540; the most recent is a minimum estimate of 236. Although the Greater Yellowstone population is relatively close to recovery goals, the plan's definition of recovery is controversial. Thus, even though the population may be stable or possibly increasing in the short term, in the longer term, continued habitat loss and increasing human activities may well reverse the trend.

Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri) have suffered considerable declines since European settlement, but recently began flourishing in some areas. Especially in Yellowstone Lake itself, long-term records indicate an almost remarkable restoration of robust populations from only three decades ago when the numbers of this fish were depleted because of excessive harvest. Its current recovery, though a significant management achievement, does not begin to restore the species' historical abundance.

Early accounts of pronghorn (Antilocapra americana) in Greater Yellowstone described herds of hundreds seen ranging through most major river valleys. These populations were decimated by 1900, and declines continued among remaining herds. On the park's northern range, pronghorn declined from 500-700 in the 1930s to about 122 in 1968. By 1992 the herd had increased to 536.

Among plants, whitebark pine (Pinus albicaulis) is a species of special interest, in large part because of its seasonal importance to grizzly bears, but also because its distribution could be dramatically reduced by relatively minor global warming. In this case, researchers do not have a good long-term data set on the species, but they understand its ecology well enough to project declining future conservation status. A more immediate, and serious, threat to whitebark pine is an introduced fungal disease, white pine blister rust (Cronartium ribicola), which is causing heavy mortality in the species. Occasional resistant individuals occur, but in the short to medium term, a severe population decline is expected.

Estimates of the decline of quaking aspen (Populus tremuloides) on the park's northern range since 1872 range from 50% to 95%, and perhaps no controversy underway in Greater Yellowstone more clearly reveals the need for comprehensive interdisciplinary research. Several factors are suspected in the aspen's changing status, including Native American influences on numerous mammal species and on fire-return intervals before the creation of the park in 1872; European influences on fire frequency since 1886; regional climate warming; human harvests of beaver and ungulates in the first 15 years of the park's history and of wolves and other predators before 1930; human settlement of traditional ungulate migration routes north of the park since 1872; ungulate (especially elk) effects on all other parts of the ecosystem since 1900; and human influences on elk distribution in the park.

The Yellowstone hot springs are important for their diversity of thermophilic bacteria. These bacteria have been useful in studies of the evolution of photosynthesis and as sources of thermostable enzymes for molecular biology. Although the smell of sulfur is common and there are some sulfur fixing cyanobacteria, it has been found that hydrogen is being used as an energy source by extremophile microbes.