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Twelve years after the Declining Amphibian Populations Task Force (DAPTF) was established, those who have to answer queries from other biologists and the media are still unable to say why amphibians are declining. In this chapter, I briefly discuss a number of issues concerning amphibian declines and, in so doing, will attempt to reveal some of the reasons for these declines. Declines in Protected Areas and Elsewhere Scientific and media attention in the last twelve years has been largely focused on the sudden collapses of amphibian faunas in protected areas, notably in Australia, Central America, and the Pacific Northwest of the United States. This attention is appropriate because these changes are deeply disturbing and have profound implications for conservation. In particular, the fact that amphibians can decline catastrophically in protected areas raises serious doubts about the efficacy of protection as a means for conserving biodiversity. However, there is a serious danger that by concentrating on protected areas we are overlooking the fact that amphibian populations in many parts of the world have been declining for a long time outside protected areas— perhaps less dramatically, but equally disturbing. Protecting an area eliminates only some of the environmental insults that threaten the inhabiting wildlife. Although we do not yet know with certainty the causes of any of the declines that have occurred in protected areas, there is a growing consensus that four causal factors are involved in varying degrees : climate change, pollution, increased ultraviolet B (UV-B) radiation, and disease (Alford and Richards, 1999). None of these causal factors is moderated in the slightest degree by putting a fence around an area and labeling it “protected.” Protection does eliminate one factor that threatens wildlife—habitat destruction. There is little doubt that this has been a major factor in the widespread decline of amphibian populations outside protected areas. However, protected areas are often small in area and isolated from other areas of suitable habitat. The effects of habitat destruction are obvious— amphibians disappear. The effects of habitat fragmentation are less obvious, however, and of greater importance if we are to progress to effective conservation of amphibians. The research conducted outside protected areas concerning this issue is very important, not only because it tells us a lot about the causes of population declines, but also because it influences the way we create and design protected areas. The Quest for a “Smoking Gun” Although the experience of extinction events over many years has shown that the causes for any one species are rarely clearcut , there was an implicit assumption among many who became concerned about amphibian population declines twelve years ago that there must be a single causal agent—the task was to find out what it was. Because amphibian declines were so sudden and were occurring in protected areas, there was also a presumption that we were looking for something new. As a result , both research and media attention focused on certain possible causes, while others were ignored. This has had both beneficial and detrimental effects on our efforts to understand amphibian declines. Conservation biologists are not isolated from the sociological pressures that drive science in general. To succeed in science , an ambitious researcher has to carry out groundbreaking work, reveal novel phenomena, and develop new methodologies . The amphibian decline phenomenon has provided the opportunity for some scientists to conduct well-funded, high profile research into topical issues such as ultraviolet radiation, climate change, and emerging infectious disease. Over the last twelve years, very able herpetologists who have made their reputation in other areas of biology have seized these opportunities and turned their attention to the amphibian decline problem. This has been of enormous benefit—bringing powerful minds to bear on the problem and blurring the distinction between “pure biology” and “conservation biology,” which has long been a low-prestige activity. The downside of the quest for a single, novel explanation for amphibian declines is that the familiar causes of extinction, notably habitat loss and pollution, have tended to be overlooked . I suggest that this is slowly beginning to change. Research into the ecology and population dynamics of amphibians has made it clear that their effective conservation requires much more than putting a fence around a little bit of 3 O N E Diverse Phenomena Influencing Amphibian Population Declines TIM HALLIDAY suitable habitat. Work on pollutants, and particularly on their sub-lethal effects, is suggesting that their impact is far more subtle, more varied, and more sinister than had been imagined previously. In particular...

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