Oki Liviiif; Resources — Inwrior West 



313 



species rather than over broader ecological prin- 

 ciples. GYE managers must keep at least two 

 types of "long-term" status in mind. One is the 

 known, or at least probable, trend of a species 

 based on historical and prehistorical informa- 

 tion. The second type is that which has existed 

 since the beginning of fonnal scientific study. 

 Though 20 or 30 or even 50 years of informa- 

 tion on a population may be considered long- 

 term by some, one of the important lessons of 

 GYE management is that even half a century is 

 not long enough to give us a full idea of how a 

 species may vary in its occupation of a wild 

 ecosystem. 



For example, anecdotal information on griz- 

 zly bear abundance dates to the mid-l800"s 

 (Schullery and Whittlesey 1992), and adminis- 

 trators have made informal population estimates 

 for more than 70 years (Schullery 1992). From 

 these sources, we know the species was common 

 in the GYE when Europeans arrived, and we 

 know that the population was not isolated before 

 the I930"s, but is now. We do not know if bears 

 were more or less common than now. 



A 1959-70 bear study suggested a grizzly 

 bear population size of about 175, later revised 

 to about 229 (Craighead et al. 1974). Later esti- 

 mates have ranged as low as 136 and as high as 

 540 (Schullery 1992): the most recent is a min- 

 imum estimate of 236 (Servheen 1993). 

 Although the GYE population is relatively close 

 to recovery goals, the plan's definition of 

 recovery is controversial (Mattson and Reid 

 1991; Schullery 1992). 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 (Oncorhynclnis 

 clarki bouvieri) have suffered considerable 

 declines since European settlement, but recent- 

 ly began flourishing (Varley and Schullery 

 1983) in some areas. Especially in Yellowstone 

 Lake itself, long-term records indicate an 

 almost remarkable restoration of robust popula- 

 tions from only three decades ago when the 

 numbers of this fish were depleted because of 

 excessive harvest (Gresswell and Varley 1988). 

 Its current recovery, though a significant man- 

 agement achievement, does not begin to restore 

 the species" historical abundance. 



Early accounts of pronghom {Antllocapra 

 amehcana) in the GYE described herds of hun- 

 dreds seen ranging through most major river 

 valleys (Schullery and Whittlesey 1992). These 

 populations were decimated by 1900, and 

 declines continued among remaining herds. On 

 the park's northern range, pronghom declined 

 from 500-700 in the 1930's to about 122 in 

 1968 (Houston 1982). By 1992 the herd had 

 increased to 536 (J. Mack, National Park 



Service, personal communication). 



Among plants, whitebark pine [Piiius ulhi- 

 caulis) is a species of special interest, in large 

 part because of its seasonal importance to griz- 

 zly bears, but also because its distribution could 

 be dramatically reduced by relatively minor 

 global warming (Blanchard and Knight 1991; 

 Romme and Turner 1991; Fig. 2). In this case, 

 we do not have a good long-term data set on the 

 species, but we understand its ecology well 

 enough to project declining future status. 



Estimates of the decline of quaking aspen 

 (Populus tremuloides) on YNP's northern range 

 since 1872 range from 50% to 95% (Houston 

 1982; Kay 1993), and perhaps no controversy 

 underway in the GYE more clearly reveals the 

 need for comprehensive interdisciplinary 

 research. Several factors are suspected in the 



Fig. 1. Progressively lighter shad- 

 ing is used around the edges of a 

 recent map of the Greater 

 Yellowstone Ecosystem to illus- 

 trate the uncertainty that still 

 plagues definitions of the ecosys- 

 tem. 



