In lieu of an abstract, here is a brief excerpt of the content:

Living organisms must track the climate regimes appropriate for their survival, adapt to new conditions, or go extinct. In the 1970s, climatologists began to warn that Earth would experience rapid changes, induced in part by emissions of “greenhouse ” gases resulting from the burning of fossil fuels, intensifying land use, and reduction in forest cover. They projected that global temperatures would rise substantially in the coming decades (e.g., Climate Resources Board, 1979). At approximately the same time, climatologists also became concerned that chloroflourocarborns (CFCs) and other commonly used industrial gases were depleting the earth’s protective ozone layer, thereby increasing the amount of cell damaging ultraviolet B (UV-B) radiation that reaches ground level (van der Leun et al., 1998). Scientists projected that species might concurrently respond to some of these global changes; ranges might shift, natural communities might be disrupted, and mass extinctions of some species might occur (e.g., Peters, 1988). Amphibians warrant substantial conservation attention. They are considered valuable indicators of environmental quality, and they have multiple functional roles in aquatic and terrestrial ecosystems (Blaustein and Wake, 1990; Stebbins and Cohen 1995; Green, 1997b; Lannoo, 1998b). Furthermore, amphibians provide cultural and economic value to human society (Grenard, 1994; Stebbins and Cohen, 1995; Reaser and Galindo-Leal, 1999; Reaser, 2000a). As part of the overall “biodiversity crisis,” many amphibian populations have been declining and undergoing range reductions (reviewed in Blaustein and Wake, 1995; Stebbins and Cohen, 1995; Reaser, 1996a, 2000a). Indeed, during the past decade, the amphibian decline issue has come to be regarded as an ecological emergency in progress. More than a dozen amphibian species are believed to have recently gone extinct, and the population ranges of many species have been dramatically reduced (Stebbins and Cohen, 1995). Numerous anthropogenic factors have been implicated as causes of amphibian population declines (see Blaustein and Wake, 1995; Stebbins and Cohen, 1995; Reaser, 1996a, 2000a; Blaustein et al., 2001; Hayes et al., 2002a,c; Kiesecker, 2002; Halliday, this volume; Crump, this volume; Blaustein and Belden, this volume; Bridges and Semlitsch a,b, this volume; Beasley et al., this volume). These factors operate across multiple scales, often have synergistic relationships, and can trigger a cascade of impacts on biological communities. For many such reasons, the site-specific causes of amphibian population declines have been difficult to assess. Habitat destruction and the introduction of invasive alien species (e.g., Tilapia, trout) are readily apparent causative agents at some sites, and they present obvious resource management and policy options. However, amphibian population declines in areas with little human activity, especially those in protected reserves, invoke particular concern (e.g., Pounds and Crump, 1994; Lips, 1998, 1999; Pounds et al., 1999). Where amphibians are declining without apparent cause, it is difficult to arrest these declines or to identify what the implications are for the rest of the biological community (including humans). Recent studies investigating site-specific cases of amphibian declines have revealed that global changes may be involved. Regional warming, increases in ultraviolet radiation, and disease epidemics may all be driven by global phenomena. These global changes might be induced, at least in part, by the increasing intensity and extent of the human impact on climatic and ecological systems. Global Warming Severe declines in frog populations at Monteverde Cloud Forest Preserve, Costa Rica, were first noted in 1988 when only eleven golden toads (Bufo periglenes) of the 1,500 adults noted the previous year showed up to breed. The last of the species, a single adult male, was observed the following year (Pounds and Crump, 1994; Crump, this volume). Over the following decade, 40% of the amphibian species at Monteverde were decimated in a series of synchronous crashes (Pounds et al., 1999). The rapid declines in Monteverde occurred during peaks of warm and dry conditions, leading scientists to suspect that the frogs had been physiologically stressed through moisture limitation . Pounds et al. (1999) found that the dry season at Monteverde has indeed become warmer and drier. Furthermore, the dry days are now sustained in longer runs. Pounds et al. hypothesized that the cloud bank in this montane cloud forest has lifted, decreasing misting and condensation. A model produced by a separate team of scientists (Still et al., 1999) to simulate the effects of global warming on tropical montane 60 E LEVE N Repercussions of Global Change JAMIE K. REASER AND ANDREW BLAUSTEIN cloud forests lends credence to this hypothesis. In addition to amphibian disappearances, populations of two species of lizards disappeared and the ranges of...

Share