ABSTRACT
The global diversity and status of both amphibians and reptiles at the end of the 20th century were described in thorough detail in the previous edition of the current volume (McDiarmid and Mitchell 2000). During the 1990s, however, it became clear that the diversity and status of amphibians were changing rapidly, with substantial declines in amphibian populations in many regions (Alford and Richards 1999). There has also been widespread concern regarding possible increases in the prevalence of developmental abnormalities and malformations in amphibians (Johnson et al. 2003). Great advances have been made in understanding these problems since 1999. This chapter concentrates on defining the problems, illustrating and interpreting our understanding of their causes, and developing ideas regarding how the problems can be managed.
