The amphibian decline crisis: A watershed for conservation biology?

Amphibians have declined dramatically in many areas of the world. These declines seem to have worsened over the past 25 years and amphibians are now more threatened than either mammals or birds, though comparisons with other taxa are confounded by a shortage of reliable data. Research into amphibian declines has focused on: (1) documentation at the landscape or population level; and (2) observational and experimental work on potential causes of declines. Although loss of habitat is known to have impacted amphibians for decades, recent research has focused on the effects of environmental contaminants, UV-B irradiation, emerging diseases, the introduction of alien species, direct exploitation, and climate change. Such factors may interact with each other, but high levels of mortality do not necessarily lead to population declines. Major challenges remain in extrapolating from experimental data to population level effects, and in developing methodologies that will provide unbiased descriptions of amphibian population dynamics. Although amphibians have been widely advocated as good biological indicators, there is little evidence to suggest that they are more effective than other taxa as surrogate measures of biodiversity or habitat quality. As many of the threats facing amphibians are extremely difficult to neutralize in the short- to medium-term, the chances of ameliorating - let alone reversing - amphibian declines seem very poor.