Rana muscosa (mountain yellow‐legged frog) was eliminated by introduced fishes early in this century in many of the lakes and streams in Sequoia and Kings Canyon National Parks, California. In waters not inhabited by fish, however, R. muscosa has disappeared from many sites within the parks during the past 30 years, and it appears to have gone extinct in some drainage systems. Fragmentation of populations may have caused or contributed to these recent extinctions, because R. muscosa populations are significantly more isolated from one another by fish at present than in prestocking conditions. A total of 312 lake‐sites in 95 drainage basins were surveyed for amphibians and fish in 1989–1990. For the 109 sites containing R. muscosa, we delineated networks of sites connected to one another via fishless streams, and we compared these present fishless networks (“present networks”) to those expected for the same sites assuming that fish had not been introduced to the parks (“former networks”). Most present networks consist of only one site (mean = 1.4), whereas the former networks average 5.2 sites. This difference represents approximately a 10‐fold difference in connectivity of populations, which is defined as the mean number of potential dispersal links (fishless streams) per network. Connectivity averages only 0.43 in present networks, in contrast to 4.15 in former ones.
The major challenge to stewardship of protected areas is to decide where, when, and how to intervene in physical and biological processes, to conserve what we value in these places. To make such decisions, planners and managers must articulate more clearly the purposes of parks, what is valued, and what needs to be sustained. A key aim for conservation today is the maintenance and restoration of biodiversity, but a broader range of values are also likely to be considered important, including ecological integrity, resilience, historical fidelity (ie the ecosystem appears and functions much as it did in the past), and autonomy of nature. Until recently, the concept of “naturalness” was the guiding principle when making conservation‐related decisions in park and wilderness ecosystems. However, this concept is multifaceted and often means different things to different people, including notions of historical fidelity and autonomy from human influence. Achieving the goal of nature conservation intended for such areas requires a clear articulation of management objectives, which must be geared to the realities of the rapid environmental changes currently underway. We advocate a pluralistic approach that incorporates a suite of guiding principles, including historical fidelity, autonomy of nature, ecological integrity, and resilience, as well as managing with humility. The relative importance of these guiding principles will vary, depending on management goals and ecological conditions.
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