May 2007
Figure 1.
The Golden Toad, once abundant in Costa Rica, has not been seen since the late 1980s. Photo: U.S. Fishery and Wildlife Service.
Amphibians have been around for over 360 million years, enduring at least three mass extinction events including the one that eliminated the dinosaurs. However, it remains to be seen how they will fare through the current extinction event. A recent Global Amphibian Assessment revealed that
- nearly half of all amphibian species are declining
- one-third to one-half are threatened with extinction
- over 120 species have become extinct in recent years1
Amphibians seem to be faring worse than other taxa; for every threatened species of bird or mammal, there are two to three species of amphibian threatened with extinction.
Why are amphibians important to our well-being?
Amphibians profoundly enhance our lives and our world in countless ways:
They provide vital biomedicines, including analgesics and antibiotics.2 A compound capable of preventing HIV infection has been found in the skin of the Australian red-eyed tree frog (Litoria chloris) and several related species.3
Amphibians are also indicators of environmental health. Trace amounts of the herbicide atrazine in the environment and in our drinking water are capable of chemically sterilizing developing tadpoles.4 Are amphibians modern-day canaries in the coal mine, warning us of worsening conditions that may one day threaten us?
Amphibians are also vital components of their ecosystems, and in some regions a single amphibian species can exceed the biomass of all the bird or mammal species combined.5
Amphibians have also played an important role in human culture, from religion to fables and traditional medicines.6,7
Why are amphibian populations declining?
Amphibian extinctions are caused by diverse factors, with habitat loss as one of the most significant threats impacting 90 percent of those species currently considered threatened. But a recently described fungus, Batrachochytrium dendrobatidis, has been receiving much scientific scrutiny in the past decade.
Figure 2.
Southern Corroboree Frog populations, once numerous in Australia, have declined by 80% in the last decade. Photo: Taronga Zoo.
This parasite was previously thought to infect only vascular plants and invertebrates, but now it has been connected to dying amphibians on every amphibian-inhabited continent. For example, scientists have observed how amphibian populations in the mountains of Central America quickly suffered a 50 percent loss of species and an 80 percent loss of individuals after arrival of the fungus, and that the disease is spreading southeast through the isthmus at about 28 kilometers per year.8
Can the killer fungus be stopped?
It has been posited that amphibian chytrid is native to South Africa where it lives symbiotically with the African clawed frog.9 Since the 1930s, these frogs have been distributed around the world by the tens of thousands, initially for use in human pregnancy tests. Although it is easily treated in captivity, the disease cannot be stopped in the wild, and massive extinctions are predicted as it continues to spread around the world. Amphibian chytridiomycosis has been called “the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted and its propensity to drive them to extinction.”10
Although the scientific community has been aware of and is monitoring the developing problem for several decades, intervention has not been a unified priority. In 2005, the global conservation community united and stated, “it is morally irresponsible to document amphibian declines and extinctions without also designing and promoting a response to this global crisis.”4,10 An Amphibian Conservation Summit was convened with the world’s amphibian authorities from academia, zoos, governments, veterinary medicine, and other diverse disciplines. A declaration was produced calling for an Amphibian Conservation Action Plan (ACAP) to address the extinction crisis and establish the Amphibian Specialist Group (ASG) to carry out that plan.11 The ACAP calls for four lines of action:
- Research—expand understanding of causes of declines
- Assessment—document amphibian diversity and its changes
- Conservation—develop long-term conservation programs
- Rapid response—intervene against imminent extinctions
The overall budget for these initiatives in the first five years is estimated at $400 million. Although this seems like an impossibly large sum, it is less than the cost of two 747 airplanes and just 0.1 percent of the US war budget in the Middle East. It is only about a quarter of what US federal and state agencies currently spend on endangered and threatened species in a year ($1.4 billion), and it’s just three times what these agencies spent on their top recipient, the Chinook salmon ($161,309,500), a single sport and commercial fish species that is being deliberately introduced in parts of North America.
While the ACAP’s greatest conservation priority is in situ action, that is, in the wild (as opposed to ex situ, in a controlled situation such as a lab), some threats like chytrid fungus cannot be addressed in the wild. Without immediate captive management as a stopgap component of an integrated conservation effort, hundreds of species will become extinct. The World Conservation Union, IUCN, has urged that “all critically endangered and extinct in the wild taxa should be subject to ex situ management to ensure recovery of wild populations,” and the ACAP white papers echo that assertion: “Survival assurance colonies are mandatory for amphibian species that will not persist in the wild long enough to recover naturally once environments are restored; these species need to be saved now through ex situ measures so that more complete restoration of ecosystems is possible in the future.”10 Comparable calls to action are included in the Global Amphibian Assessment and other documents.
What can the Amphibian Ark do?
Fortunately, a thriving industry already exists that specializes in captive management of animals. Zoos and related facilities number over 1200 institutions with more than 100,000 employees and attract about 600 million visitors per year. Zoos have the capability to assist with the following:
- rapid response rescues
- captive assurance colonies
- providing animals for release and research
- conservation education
- capacity building
- fundraising
- helping to develop recovery plans
The World Association of Zoos and Aquariums (WAZA) has joined with the Conservation Breeding Specialist Group (CBSG) and ASG to form the Amphibian Ark, or AArk for short. The AArk vision is the world’s amphibians safe in nature. Its mission is to work with partners to ensure the global survival of amphibians, focusing on those that cannot be safeguarded in nature. AArk is rapidly developing capacity to coordinate ex situ programs implemented by partners around the world, with the first emphasis on programs within the range countries of the species. At the same time, it maintains constant attention on its obligation to couple ex situ conservation measures with necessary efforts to protect or restore species in their natural habitats. Its activities include these:
provide strategic guidance on activities to all stakeholders, such as zoos, wildlife agencies, universities
consult on species-specific issues, for example, reintroduction, gene banking, and veterinary, legal, and ethical concerns
coordinate all aspects of implementation within the AArk initiative
assist AArk partners in identifying priority taxa and regions for ex situ conservation work
lead development and implementation of training programs for building capacity of individuals and institutions
develop communications strategies, messages, and materials to promote understanding and action on behalf of amphibian conservation
The AArk’s Conservation Plan is one part of the comprehensive ACAP; the ex situ component may help stave off many extinctions, but safeguarding these species in situ will be the ultimate measure of success. In 2008, AArk will lead zoos in a globally coordinated public awareness campaign, “The Year of the Frog.” The publicity campaign will help leverage a simultaneous worldwide capital campaign managed at the level of the individual institutions.
What are the challenges?
The ex situ conservation community faces many challenges to meet expectations, first and foremost of which is rapidly increasing capacity. It is estimated that the global zoo community can currently manage viable populations of around 50 amphibian species, which amounts to perhaps 10 percent of those requiring ex situ intervention. One solution is to have zoos construct additional biosecure facilities where needed, ensuring that keepers are trained and resources are appropriately allocated to support this action. Of course, some zoos are already making valuable contributions to amphibian conservation. Some are constructing dedicated facilities on grounds, and some are helping to develop facilities in other regions of the world. Zoos are leading dozens of amphibian conservation programs, including habitat restoration, translocations, conservation education and research,12 and region-wide amphibian community rescues.13 There are now several zoo-led courses designed to develop husbandry expertise, including AZA’s amphibian biology and management course, which has spawned similar courses in Mexico, Ecuador, and Colombia.
Amphibians are vitally important as
- integral components of ecosystems5
- indicators of environmental health4,14
- contributors to human health2,3
Amphibians persisted as the dinosaurs came and went, but today as many as half of all species are threatened with extinction. We are only just beginning to understand the impacts of their disappearance.15,16 Addressing the amphibian extinction crisis represents the greatest species conservation challenge in the history of humanity. The global conservation community has formulated a response, and an integral part of that response is the Amphibian Ark, in which select species that would otherwise go extinct will be maintained in captivity until they can be secured in the wild. Without immediate captive management as a stopgap component of an integrated conservation effort, hundreds of species may become extinct.
© 2007, American Institute of Biological Sciences. Educators have permission to reprint articles for classroom use; other users, please contact editor@actionbioscience.org for reprint permission. See reprint policy.
