new habitats, new infectious diseases have emerged that have real or potential consequences, not only for humans, but also for many other taxa, such as the case of Bd and amphibians (Cunningham et al., 2006). Perhaps the most profound impact is the human role in climate change, the effects of which may have been relatively small so far, but which will shortly be dramatic (e.g., in the sea) (Jackson, Chapter 1, this volume). Research building on the Global Amphibian Assessment database (SN Stuart et al., 2004) showed that many factors are contributing to the global extinctions and declines of amphibians in addition to disease. Extrinsic forces, such as global warming and increased climatic variability, are increasing the susceptibility of high-risk species (those with small geographic ranges, low fecundity, and specialized habitats) (Sodhi et al., 2008). Multiple factors acting synergistically are contributing to the loss of amphibians. But we can be sure that behind all of these activities is one weedy species, Homo sapiens, which has unwittingly achieved the ability to directly affect its own fate and that of most of the other species on this planet. It is an intelligent species that potentially has the capability of exercising necessary controls on the direction, speed, and intensity of factors related to the extinction crisis. Education and changes of political direction take time that we do not have, and political leadership to date has been ineffective largely because of so many competing, short-term demands. A primary message from the amphibians, other organisms, and environments, such as the oceans, is that little time remains to stave off mass extinctions, if it is possible at all.
We thank M. Koo for producing Figs. 2.1, 2.2, and 2.5 [using methods from Gastner and Newman (2004) and data from SN Stuart et al. (2004), AmphibiaWeb (2007), and Global Amphibian Assessment (2007)]; K. Klitz and R. Diaz for help with Fig. 2.4; colleagues who aided in collecting and analyzing data; C. Briggs, R. Knapp, and T. Tunstall (Sierra Nevada) and M. Garcia-Paris, G. Parra-Olea, and J. Hanken (Mexico) for discussion; J. Avise and J. Jackson for comments on this manuscript; and M. H. Wake for a thorough review of the manuscript and extensive discussion. This work was supported by National Science Foundation Grant EF0334939 (to D.B.W.) and National Institutes of Health/National Science Foundation Ecology of Infectious Disease Program Grant R01ES12067 [to C. Briggs (University of California, Santa Barbara)].