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Wetland Woes (WWW) Amphibian Declines and Malformations by Michael J. Lannoo Posted December 24, 1999 ˇ Issue 69 Abstract Amphibian population declines have provoked a number of studies, both good and bad, into their causes. Public opinion about this problem has been driven in part by researchers who don't adhere to the scientific method, and Web sites that disseminate anecdotal information. Over the past decade, both scientists and the general public have expressed concern, even alarm, over the frequent media reports of declining and malformed amphibians. Most often, these reports note that amphibians act as "canaries in the coal mine," serving as early warning signals for an environmental collapse that will affect humans. But as David Wake at the University of California at Berkeley points out, this analogy does not truly hold: while miners have the option of leaving their poisoned environments, humans do not yet have the option of leaving Earth en masse. In addition to this concern for human health, there is a concern for the amphibians themselves, and for the natural ecosystems that support them. Two decline scenarios arise: (1) amphibians are dying because ecosystems are sick (the canary argument), and (2) amphibians are being targeted and ecosystems are dying because amphibians are sick. This latter scenario recognizes the important roles that amphibians, even single species, play as herbivores, carnivores, and prey in aquatic and terrestrial ecosystems. In any scientific investigation - and certainly dealing with such critical issues as these - it is imperative that all parties adhere to a rigorous scientific process. Unhappily, as we shall see later, in the field of amphibian decline research, this is by no means always the case. Personal and political agendas can hinder the most promising efforts. Many causes for amphibian declines have been proposed. These include habitat loss and alteration; agricultural, industrial, and lawn chemical applications or discharges; ultraviolet-B radiation; aquaculture (especially fish farming); global warming; and disease outbreaks. Each of these proposed causes indeed affects amphibians, but the relative importance of each depends on the region, species, and time frame being considered. Some of these causes (for example, habitat loss and fish farming) affect ecosystems, which in turn affect amphibians. Other causes (diseases such as the recent epizoic chytrid fungus outbreak) affect amphibians, which in turn affect ecosystems. It is likely that in most regions, amphibians experience a combination of threats (for example UV-B and pesticides) that interact with each other in ways that we do not yet fully understand. Despite the media attention and the best efforts of scientists to determine causes, amphibian declines continue. And with the possible exception of perhaps half a dozen (out of about 230) species, all U.S. amphibian species are currently in decline. These declines are occurring, if for no other reason, because habitat is continuously being lost. Amphibian species will continue to decline until one of two things happens: (1) we exhibit the political (i.e., social) will to stop the causes of these losses, or (2) species become extinct. Overlaid on the issue of amphibian declines is the problem of amphibian malformations. Here, some patterns emerge, as follows: (1) Reports of malformed amphibians are not a new phenomenon, they extend back to at least the mid-1700s. (2) David Hoppe, at the University of Minnesota at Morris, has discovered that when compared with historical malformations, the current malformed frog phenomenon involves more sites and higher numbers of animals within each site, and that recent malformations tend to be more severe. (3) In the Midwest, wetland hotspots of amphibian malformations appear to be isolated, surrounded by wetlands with normal animals, and affected and normal wetlands can be within the home range of single individuals. (4) In hotspots, more than one species can be affected. (5) Different sites have different types of malformations. (6) At hotspots, structures other than limbs, including orbital and other cranial features, visceral features, edemas, and pigment abnormalities have also been reported. (7) New types of malformations continue to be reported; some of these represent more severe defects than have been reported at the same sites in the recent past. (8) Xenobiotic chemicals, parasites, and UV-B radiation have been shown to cause amphibian malformations in the laboratory. (9) Discussions of experimental data sets have tended to focus on single causes of malformations, without adequately demonstrating that these causes indeed have produced the malformations that we see in nature. A consideration of these facts suggests that there is a natural cause of amphibian malformations (perhaps parasites), but that superimposed upon this background level is some more recent, more potent, and widespread cause. My own data set (gathered from radiographs of almost 600 animals of 16 species from 59 sites scattered through ten states) suggests that there is more than one cause of amphibian malformations, and that these causes vary geographically. I coordinate the U.S. Working Group of the Declining Amphibian Populations Task Force, a group composed of about 1,200 people. In this position I have two duties: (1) to serve as a switchboard, connecting people with questions to people with answers; and (2) to assist in guiding initiatives and programs in the right direction. And while this latter duty seems self-righteous, even pompous, it is, in fact, an easy task. Any program that uses the scientific method - observation to hypothesis to hypothesis testing - as a basis for information gathering or dissemination meets our guidelines. Using the scientific method, we note that facts can never prove hypotheses correct, they can only prove alternate hypotheses incorrect. And we note that facts take priority over hypotheses. This is the process T.H. Huxley championed when he quipped: A beautiful hypothesis destroyed by one nasty, ugly little fact. Unfortunately, neither every person nor every group with an interest or position in the field of amphibian conservation biology (or science in general for that matter) follows this scientific process. In amphibian conservation we have true scientists, of course, but we also have people who cannot separate facts from opinion, people who act like preachers (sticking to hypotheses independent of the facts), and people who act as lawyers (knowing the facts but twisting them to fit their favorite hypotheses). One example of this comes out of the response to last summer's drought, which brought forth a call from a subset of U.S. Geological Survey (USGS) biologists for "anecdotes about the effects of drought on amphibians." This followed a request, made earlier this spring by the same USGS group, for opinions on species to be included in a top ten list of amphibians in most severe decline. Fortunately, many scientists felt, and made their opinions known, that this group should not be in the business of collecting anecdotes and opinions when real data were available, and that these activities did not represent the goals of the USGS at all. Unfortunately, Internet access promotes this sort of nonscientific activity. It is now common in scientific papers to find Internet citations replacing comparable peer-reviewed publications. A second example comes from the attempt to determine causes of malformations. Here, originators and/or proponents of causes sometimes assume (erroneously, in my opinion) that their good reputations depend on their views being completely correct and/or all-encompassing. They then seek to defend these views against all alternatives. In doing so, they become preacherlike or lawyerlike and trample the scientific method. It is an open secret that one researcher has gone so far as write letters to Donna Shalala, U.S. secretary of health and human services; Bruce Babbitt, U.S. secretary of the interior; and Jesse Ventura, governor of Minnesota. The purpose of these letters was an attempt to censure, through a repeal of peer-reviewed grant funding, ongoing projects that contradicted the author's hypothesis. Many view this action as cowardly; several have suggested it is academic misconduct. I only note that the major transgression is nonscientific behavior. The Washington Post reporter William Souder will be detailing some of these activities in his upcoming book A Plague of Frogs, to be published through Hyperion Press this coming March. In closing, I emphasize that no, the future for amphibians does not look bright (continued losses, however slight, cannot be sustained; new types of malformations continue to be reported); and yes, there is a lot of nonscience (much of it nonsense) being propagated through Web sites and mailing lists. But the public is interested, the public cares, and a silent majority of scientists understand and practice the scientific method. And in this we take hope. Michael J. Lannoo received his doctorate at Dalhousie University in Halifax, Nova Scotia, Canada, in 1986. He is currently an associate professor of neurobiology in Indiana University's Muncie Center for Medical Education at Ball State University. Alexandria Heather-Vazquez is art director of HMS Beagle. |
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