Disappearing Jewels: Chapter 4
Given the array of threats facing New World amphibians, what actions can we take to improve their chances for survival in the decades to come? A mix of short-term and long-term actions is needed, and the challenge requires the participation of scientists, conservationists and policy-makers in dozens of countries. Stemming the tide of coming extinctions will require strengthening protected areas systems, improving legal protections and public policies, strategically using captive breeding, raising public awareness, and finding the answers to critical questions about the life history of amphibians and what threatens them.
=Habitat protection
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Many New World nations now have published lists of endangered species recognized by the government. Legislation creating these lists is an important start in protecting these species from extinction. Yet these lists can use two important reforms.
First, lists in many countries were drawn up without access to all available population data for the entire amphibian fauna. Thus many of these lists need to be brought up to date to reflect current knowledge of taxonomy and threat status. The information provided in our assessment can be an important input into the process. Although the Global Amphibian Assessment uses the IUCN Red List criteria for defining threat status, the supporting data for the individual species assessments are readily available on the Internet and can be used as input into other threat assessment schemes, such as one used in Argentina designed specifically for amphibians and reptiles[4]. Regardless of which system is used, national lists should reflect the current state of knowledge.
Second, endangered species legislation tends to fall under wildlife law. One often finds lists of endangered species in laws regulating hunting and fishing. Specific penalties are listed for killing a threatened animal. While the situation varies by country, often the laws do nothing to prevent the loss of essential habitat, such as damming a river that is the only home for an endemic frog, or converting a diverse forest that is critical salamander habitat into a pine plantation. With input from stakeholders such as conservationists and landowners, public officials should revise endangered species legislation to protect habitats as well as safeguard species from direct persecution.
National legislation also needs to address trade in amphibian species. As we have seen, bullfrog farms can threaten native amphibians by being a source of escaped frogs or diseases, either of which can decimate local faunas. The African clawed frog may also be an important vector of disease. Extreme safety measures should be used to prevent escape into the wild. Unrestricted exploitation and trade of native species can diminish local populations to the point of local extinction and can lead to the global spread of serious diseases. Imported animals should be quarantined and examined for all known amphibian diseases, including Bd. Trade in native species can be achieved in a sustainable manner, but must be regulated based on ongoing population monitoring. Finally, trade in species known to transmit diseases should be banned or severely restricted[5].
Captive breeding
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Captive breeding is a conservation tool that can be employed in concert with habitat protection. Habitat protection is much less costly than captive rearing and often more effective, and therefore it should be the normal course of action for the conservation of small populations. In some cases, such as when disease threatens, habitat protection alone may not be sufficient. Examples include the protection of highland species of harlequin toads, Telmatobius frogs, stream dwelling treefrogs, Eleutherodactylus frogs, and glass frogs, all of which are known to be susceptible to the disease Bd. Currently, no management technique is available to prevent wild populations from being wiped out by the disease. When a species is vulnerable to disease, captive breeding should be considered. Ideally, to ensure genetic diversity in breeding stock, animals should be captured before a population becomes too small. Of course, habitat protection or restoration is essential, too, so that suitable areas exist for the release of captive-reared individuals.
To be successful, captive rearing programs must make use of the best available husbandry techniques for the target species. Methods of inducing reproduction in captivity are only just being developed for many tropical species, so specialists need effective mechanisms for rapidly communicating promising new techniques to the zoo community. In some cases, hobbyists may have useful rearing techniques they can share with professional keepers. Multiple captive populations of each species should be established to maintain genetically diverse breeding stock and as a hedge against unexpected loss at any one rearing site.
Conservationists must also address the contentious issue of the captive rearing of species native to developing countries. Funding and facilities are more likely to be available in developed countries, but developing countries are understandably reluctant to surrender their dwindling biodiversity to wealthy foreign zoos. One solution is the transfer of technology and capacity to developing countries so they can rear threatened native species in their own facilities. Another possibility is negotiating ownership rights such that source countries retain ownership over frogs exported to foreign zoos for captive rearing.
Conservationists should be aware that although many threatened species can breed in captivity, very few have been successfully reintroduced into the wild (see Box 10). The added factor of the highly virulent chytrid disease in a vast geographic range further complicates reintroduction efforts. Once Bd becomes established in a region, reintroduction of susceptible amphibians will be futile until Bd can be controlled in the wild. Captive rearing can therefore maintain living animals but, at the moment, is not always a reliable method of averting amphibian extinction in the wild. Further research on reintroduction techniques may some day improve these odds.
Education and awareness
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Although the popular media has alerted the public to amphibian declines, we need greater penetration into the public consciousness of the message that amphibians are in big trouble almost everywhere. This report shows that amphibians are disappearing far faster than any other group of organisms that has been comprehensively assessed using the Red List criteria. The large number of critically endangered species, many of which may already be extinct, indicates that we are seeing only the tip of the extinction iceberg. Deeper public awareness of the problem will encourage governments to put more amphibians on endangered species lists, donors to fund more conservation and research projects on amphibians, and conservationists to include amphibians in their analyses of areas in need of protection. It could also strengthen regulations protecting wetlands and other habitats used by amphibians.
To achieve this goal, both scientists and conservationists should highlight the plight of local species in the media and include amphibian conservation in outreach programs. To reach schoolchildren, educators and scientists should work together to develop classroom materials on amphibian conservation. Scientists can also help schools and nature centers by leading walks in search of amphibians in local habitats to enhance appreciation for these often overlooked creatures. Zoos, natural history museums, and art galleries can sponsor special exhibits centered on amphibians. Schools, rural hotels, nature preserves, and parks can create artificial fish-free ponds to attract amphibians and better acquaint the public with them. In addition—especially in tropical montane areas—these ponds are important conservation tools to buffer against droughts that cause natural pools to dry up before tadpoles can undergo metamorphosis.
Additional research
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Disappearing Jewels demonstrates that scientists have come a long way toward understanding amphibian declines since reports of population crashes first began circulating in the late 1980s. Most declines are caused by habitat destruction, and no research is needed in most cases before protection of critical habitats can proceed. Over the next century, climate change will become a major threat and, again, we clearly need to protect habitats that may become favorable for threatened species as climates change. The major challenge facing field researchers today is how to prevent diseases from wiping out populations of amphibians (see Understanding Disease below).
The effects of contaminants on amphibian populations also remains poorly studied. How do the endocrine changes induced by pesticides such as atrazine translate into population level changes? Dozens of agrochemicals now find their way to amphibian habitats worldwide. How do these affect amphibian reproduction and survival? How does contaminant-induced stress influence the immune system? Scientists know very little about the effects of agrochemicals on amphibians in tropical environments. Are these effects any different than those measured in temperate environments? We know that wind can blow contaminants far into protected areas. How does this affect populations?
Despite major advances in recent years, amphibians remain poorly known creatures. For one-fifth of the species evaluated, scientists do not know enough to assign a threat category. Reasons cited include doubts about taxonomic status, incomplete range information, or a lack of recent abundance and population trend data. Future research should focus on filling in the gaps for these data-deficient species.
Finally, this analysis demonstrates the urgent need for population monitoring. Many species seem to have declined and even disappeared without anyone witnessing the event. We have no better than a vague idea when the declines occurred and have no specimens collected during the decline to give us clues to why it happened. We clearly need rigorous monitoring programs in a wide variety of habitats and on a wide variety of species to better document and understand population changes in the future. Properly designed monitoring programs should encompass not only amphibian populations but also environmental variables if we are to understand the causes of population change[6]. Future iterations of this hemispheric amphibian assessment will provide a measure of how well we are accomplishing our conservation goal.
A danger of publishing a Red List of threatened animals is that local agencies responsible for issuing research and collecting permits may become reluctant to allow scientific research on endangered species. This behavior is counterproductive. Research is essential to improving our understanding of the natural history of and threats to endangered species. Permitting agencies should therefore strive to facilitate research on endangered species by reputable scientists.
Understanding disease
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Although habitat destruction is the primary factor affecting threatened amphibians, the disease Bd has undoubtedly played a major role in pushing formerly common species to, if not over, the brink of extinction. These effects have occurred recently, perhaps in the last 30 years. Understanding Bd better and learning how to manage it in wild populations are the most important priorities for preventing future amphibian extinctions.
Researchers face many key questions about the biology of Bd. Exactly how does the disease spread over short and long distances? Understanding mechanisms of disease spread will help prevent the disease from reaching unaffected populations. How does it persist in the environment? Are there animals that serve as “reservoir” hosts for which the disease is not lethal? Answering this question will explain how the disease can persist in an environment even when all susceptible frogs have disappeared. Can species that are normally solitary and do not enter the water become infected? Some species not associated with water (such as some coquí frogs in Puerto Rico) have suffered population declines but the involvement of Bd is still unclear. How do climate change events, especially periods of drought, interact with the disease cycle? Several studies point to a connection between droughts and disease outbreaks, but how these factors interact remains a mystery. Are other diseases also causing widespread declines? Perhaps Bd is not the only major killer involved.
Finally, and most importantly, how do we eliminate the disease from a habitat once it arrives? Until we answer this conundrum we will only be able to watch as populations continue to become infected and disappear. Moreover, we will have no success at reintroducing captive-reared species that are susceptible to Bd. Fortunately many scientists are now focusing their research on Bd biology. New discoveries are emerging regularly from labs all over the world, and our hope is that we will learn how to manage the disease before all susceptible [[population]s] are gone for good.
