In recent years scientists and conservationists have raised the alarm that amphibians are disappearing before our very eyes. Even in seemingly pristine habitats, more and more of these dazzling denizens of our forests, deserts, streams, and wetlands have gone missing. But reports so far have been limited in geographic and taxonomic scope. Are these declines widespread or are they limited to a few localized areas? Are amphibians suffering from the general biodiversity crisis in the same manner as other well-publicized groups such as birds or mammals, or is something fundamentally different happening to amphibians?
This report on the New World findings of the Global Amphibian Assessment (GAA) addresses these questions by providing a comprehensive analysis of the conservation status of all the amphibians of North, Central, and South America and the Caribbean. We focus on the New World because of the continuity of land masses and evolutionary relatedness of the species found there. For each species, we compiled information about taxonomy, distribution, abundance and population trend, natural history, threats, and conservation measures. These data formed the basis for applying the IUCN Red List criteria to categorize species based on their conservation status. Overall, 229 scientists contributed to the database that forms the basis of this report.
- The New World is home to more than half of the world’s 5,743 known species of amphibians (frogs, toads, salamanders, and caecilians). Its 3,046 species represent 53% of the world total.
- Brazil and Colombia have the greatest diversity of amphibians in the world, with 731 and 698 species respectively. The top five countries for amphibians (including Ecuador, Peru and Mexico) are all in the New World, and Venezuela and the United States are also in the top 10. At the low end of the diversity scale, a number of Caribbean island nations have just one native amphibian species each.
- Nearly two out of five New World amphibians (1,187 species, or 39%) are threatened with extinction, including 337 species that are classified as Critically Endangered—on the brink of extinction. Nine species have gone extinct in the past 100 years. Another 117 species are “possibly extinct,” meaning that scientists are unaware of any extant population but have not performed the extensive searching required to place these species in the Extinct category. Many of these declines are recent: since approximately 1980, four species have gone extinct, and 109 additional species possibly have become extinct.
- From a regional perspective, amphibians in the Caribbean are most threatened (84% of the region’s 171 species), followed by Mesoamerica (Mexico through Panama) with 52% of its 685 species, South America (31% of its 2,065 species), and North America (21% of its 262 species). The global average is 32.5%.
- With 39% of the species threatened, the risk facing New World amphibians is considerably higher than for either birds (10%) or mammals (16%) in the same region.
- While threatened amphibians occur nearly everywhere, they are concentrated in several places: Haiti; montane southeastern Chiapas, Mexico through central Guatemala; montane Costa Rica and western Panama; the Andes of Colombia and Ecuador; and the central portion of the Atlantic Forest in eastern Brazil.
- Amphibians occurring at high elevations, having restricted distributions, and characterized by terrestrial life cycles (rather than those using a mix of aquatic and terrestrial habitats) are more likely to be threatened than are species with other characteristics.
- Two major and several minor threats face amphibians. Habitat loss causes a gradual contracting and fragmentation of populations and is by far the most prevalent threat, affecting 89% of all threatened species. Habitat loss is primarily caused by expanding agriculture, logging, and infrastructure development (for example, industrialization, road building, and housing developments). A second factor, a recently discovered chytrid fungal disease, has caused or is suspected to have caused precipitous declines in many species, including nearly half (47%) of all Critically Endangered and one-quarter of all threatened species. Other important threats include environmental contaminants (26% of species) and intrinsic factors such as restricted range size (23%). Climate change has already begun to affect some species; a separate analysis predicts that it will become a major threat to amphibians during the 21st century.
- The Western Hemisphere’s existing system of public and private parks and reserves provides no protection for more than one-third (37%) of threatened amphibians, emphasizing the incomplete nature of the protected area system. Even for species that are found in protected areas, management is often not effective at stemming habitat loss. Moreover, threats like climate change or disease transcend park and reserve boundaries.
- Protected Areas: Strengthen management and protection at existing reserves, and expand protected areas to cover the ranges of threatened species that are currently unprotected.
- Public Policy: Revise and keep updated existing national and subnational lists of threatened species, and strengthen legislation protecting listed species.
- Captive Breeding: Implement captive breeding for species that face a high probability of extinction in the wild, especially those threatened by the chytrid disease.
- Education: Educate the public, including schoolchildren, about the plight of amphibians, especially species of local concern.
- Research: Accelerate research on the biology of the chytrid disease with an aim toward being able to control it in the wild. Expand population monitoring and increase research on poorly known species and the effects of contaminants on amphibians.
This report leaves no doubt that amphibians are the most threatened animal group in the New World so far examined using IUCN Red List criteria. Extinctions are happening now. They will continue unless policy makers, conservationists, land managers, and the public take urgent, directed conservation action to save these disappearing jewels.
This is a chapter from Disappearing Jewels: The Status of New World Amphibians (e-book).
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