Amphibian - Conservation

Conservation

Dramatic declines in amphibian populations, including population crashes and mass localized extinction, have been noted in the past two decades from locations all over the world, and amphibian declines are thus perceived as one of the most critical threats to global biodiversity. In 2006 there were believed to be 4,035 species of amphibians that depended on water at some stage during their life cycle. Of these, 1,356 (33.6%) were considered to be threatened and this figure is likely to be an underestimate because it excludes 1,427 species for which there was insufficient data to assess their status. A number of causes are believed to be involved, including habitat destruction and modification, over-exploitation, pollution, introduced species, climate change, endocrine-disrupting pollutants, destruction of the ozone layer (ultraviolet radiation has shown to be especially damaging to the skin, eyes, and eggs of amphibians), and diseases like chytridiomycosis. However, many of the causes of amphibian declines are still poorly understood, and are a topic of ongoing discussion.

With their complex reproductive needs and permeable skins, amphibians are often considered to be ecological indicators. In many terrestrial ecosystems, they constitute one of the largest parts of the vertebrate biomass. Any decline in amphibian numbers will have an impact on the patterns of predation. The loss of carnivorous species near the top of the food chain will upset the delicate ecosystem balance and may cause dramatic increases in opportunistic species. In the Middle East, a growing appetite for eating frog legs and the consequent gathering of them for food was linked to an increase in mosquitoes. Predators that feed on amphibians are affected by their decline. The western terrestrial garter snake (Thamnophis elegans) in California is largely aquatic and depends heavily on two species of frog that are diminishing in numbers, the Yosemite toad (Bufo canorus) and the mountain yellow-legged frog (Rana muscosa), putting the snake's future at risk. If the snake were to become scarce, this would affect birds of prey and other predators that feed on it. Meanwhile, in the ponds and lakes, fewer frogs means fewer tadpoles. These normally play an important role in controlling the growth of algae and also forage on detritus that accumulates as sediment on the bottom. A reduction in the number of tadpoles may lead to an overgrowth of algae, resulting in depletion of oxygen in the water when the algae later die and decompose. Aquatic invertebrates and fish might then die and there would be unpredictable ecological consequences.

A global strategy to stem the crisis has been released in the form of the Amphibian Conservation Action Plan. Developed by over 80 leading experts in the field, this call to action details what would be required to curtail amphibian declines and extinctions over the next 5 years—and how much this would cost. The Amphibian Specialist Group of the World Conservation Union (IUCN) is spearheading efforts to implement a comprehensive global strategy for amphibian conservation. Amphibian Ark is an organization that was formed to implement the ex-situ conservation recommendations of this plan, and they have been working with zoos and aquaria around the world, encouraging them to create assurance colonies of threatened amphibians. One such project is the Panama Amphibian Rescue and Conservation Project that built on existing conservation efforts in Panama to create a country-wide response to the threat of chytridiomycosis.