Complex Mystery of Amphibian Decline Calls for a New Kind of Science
Central American forests that used to throb with the grunts, clicks, trills and chirrs of frogs have fallen eerily silent. Similar change is happening in North America and Western Australia. It is quietly alarming, and no one can explain the cause.
A group of scientists headed by James Collins, professor and chair of the Department of Biology at Arizona State University, has been awarded a grant of nearly $3 million from the National Science Foundation to study "Host-Pathogen Biology and the Global Decline of Amphibians."
Funded by the NSF's Integrated Research Challenges in Environmental Biology program, the project involves a team of 24 scientists from such different areas as evolutionary ecology, immunology, virology and mycology, and further includes specialists in statistical and molecular genetics, amphibian pathology, population biology, population ecology, ecological genetics and veterinary epidemiology, among many others.
The project is clearly not science-as-usual. Why is this research project so large? How tough can it be to find something that is wiping out frogs and salamanders on a global scale?
In familiar film and television scenarios, disaster happens because humanity has done something simple and stupid -- perhaps exploded an atomic bomb or dumped a toxic chemical. The plot is typically resolved by a sleuthing scientist who finds the cause, eliminates it, kills the giant carnivorous worms and generally cleans up the whole mess with something like baking soda -- a simple cause-and-effect problem that can be solved with a simple solution.
Real-life ecological disasters can be as dramatic as science fiction, but understanding what is causing them -- not to mention reversing the damage -- is no simple matter for contemporary science.
"Amphibian decline" is a good example. Beginning in 1989, biologists began to notice a dramatic drop in amphibian populations, in many cases to the point of extinction, in broad geographic regions around the world, including Central America, the Rocky Mountain region of North America and portions of Australia.
Explanations for the sudden and drastic loss of a large class of animals have included habitat loss through human development, competition with or predation by introduced species, pollution and climate change. Unfortunately, even all these diverse factors cannot adequately explain many of the known cases, which include multi-species extinctions on nature preserves and other relatively pristine lands.
Recently, Collins and other researchers have found evidence that a couple of different pathogens might also be involved -- one an iridovirus and the other a chytrid fungus. Both are from familiar and common groups of organisms.
"The virus is widely distributed and comes from a group that is known in fish and insects. The fungus is from a group of fungi that are cosmopolitan and are generally associated with decaying plant matter. We've known about the chytrids for a long time, but never as pathogens of amphibians until the last 18 months," said Collins.
Collins points out, however, that finding that these pathogens are a big culprit behind a broad disappearance of frogs and salamanders actually raises more questions than it answers: "Are these novel pathogens? Has the physiology of the host changed? Has the biology of the pathogen changed? Has a change in the environment altered the pathogen? Has the environment changed in a way that has caused the immunology of the host to be compromised -- and therefore the amphibian is more susceptible to something that was a natural part of its environment? These are just some of the issues that need to be considered," Collins said.
There is also the problem of the sheer scope of the phenomenon. Large tracts of land are involved, from Saskatchewan to Arizona, through Central America, and across the globe in Eastern Australia. In these areas, dozens of species have become extinct and numerous others are being threatened -- each with its own unique set of environmental conditions that may be involved.
"This project involves 24 investigators across three continents," Collins said. "It's so large because the problem is big and complicated -- the questions require an integrative, interdisciplinary approach.
"As we went through thinking about how to answer the questions, we really had to think about how we did the science. And how we did the science had to change -- it couldn't be just an individual investigator laboring away in an isolated laboratory. Rather, we imagined a set of simultaneous interactions between investigators from at least six different sub-areas. You really need a combination of specialists and then also generalists to tie everything together and keep the inquiry moving."
Working out how to plan and coordinate the project's science, Collins argues, may have a value almost as great as the research itself, and may have important implications, particularly for ecology. Not only do ecologists need to begin forming scientific partnerships with scientists from a wide array of scientific speciality areas, he argues, but the science also needs to begin incorporating knowledge and information from disciplines that are outside the traditional "hard" sciences.
"This project has implications for how you do science. In a sense, it is about defining the whole conceptual focus of ecology, particularly in that to understand this problem we have to do a better job of integrating humans into ecological and evolutionary theory. This means that ecology, as a hard natural science, will also need to start doing a better job of becoming integrated with the social sciences and probably the humanities. The nature of science itself is going to have to change," he said.
Though the project is about frogs and salamanders, humans are also on Collins' mind because, in someway or other, they are sure to be a key factor.
"Large ecological problems are expected as two major processes have begun to operate," Collins said. "One factor is global climate change, but we're also seeing the increasing homogenization of the world's fauna and flora, as organisms are moved around.
"What's driving this is globalization -- as humans become more and more integrated into the earth’s ecosystems then we're going to see more and more change. As humans move around, they move things with them, like any other animal. If there's one lesson that history teaches us, when humans move into an area, there's generally a loss of biodiversity."
While much of the ecological change caused by human influence may not be reversible or even possible to stop, Collins sees a pragmatic reason for studying problems like the amphibian decline and working hard to get quick answers.
"We'd like to be in a position where we could begin to makes some decisions that might slow up this process. If we can understand better what the dynamics are, we could do that" Collins said. "It's a three-year grant -- experiments have been planned and some are already underway. We hope to know more soon."
James Hathaway, 480-965-6375 or Hathaway@asu.edu