The Worldwide Amphibian Decline
Amphibians are extremely vital in the ecosystem as secondary food consumers since they are the prey items for vertebrates and invertebrates and control the biological pest. However, in recent years there has been a rather huge extinction of all kind of species recorded around the world. They are declining in an alarming rate, with over 43 percent of species in a state of decline (Lips et al., ND). Amphibians, such as frogs, toads, salamanders and newts, are cold-blooded animals that metamorphose from a water-breathing from into an air-breathing from and are therefore most vulnerable to any changes occurring in their habitat (National Geographic, 2008). This rather reproductive specie is lately suffering from an extremely rapid decline. Many causes remain still unknown to the modern scientists (MSNBC, 2004), although most of them agree that this mass extinction is caused by the human impact on the Earth’s environment (Rohr et al., 2008).
Decline in amphibians, mammals and birds
Amphibians have been living on the Earth for already 250 million years and have survived the five greatest mass extinctions which the dinosaurs for example didn’t (Sciencdaily, 2008). Nevertheless it is unquestionable that the newest one is more devastating than all the others since it hasn’t been caused naturally but by humans (ibid). Humans are constantly changing the climate, annihilating and polluting the environment and introducing persistent organisms. In fact 32,5 percent, which means 1’856 of the known species of amphibians are listed by the International Union for Conservation of Nature (IUCN) as globally threatened (MSNBC, 2004). In comparison, only 2 3 percent of the mammals, and 12 percent of the birds are falling into the IUCN’s categories of vulnerable, endangered of critically endangered species (Stuart et al., 2004). However, according to Stuart et al. (2004), the “level of threat to amphibians is undoubtedly underestimated because 22,5 percent (1294 species) are too poorly known to asses, as compared to only 0,8 percent (78 species) of birds and 5,3 percent (256 species) of mammal”. This comparison between all three groups shows dramatically clearly that amphibians are much more threatened than all the others, even if one might not have the impression because these animals seem often insignificant.
Reasons for decline
Amphibian decline is happening all around the world and for many different reasons. Stuart et al. (2004) divided the species suffering from rapid decline into three groups based on the causes of their decline: overexploited, reduced habitat and enigmatic decline. Species diminishing from overexploitation are usually found in East and Southeast Asia, where frogs are chased for food reasons (MSNBC, 2004).Habitat loss is occurring in Europe, North America and some Parts of Africa, where forests are destroyed or parts of the landscape turned into agricultural land. This is usually a consequence of the human population’s living standard (wasting natural resources) and growth (we need more and more space to live). The last group however, called enigmatic decline, is responsible for the most alarmingly rapid decline in amphibians. According to Stuart et al. (2004), these unidentified processes “threaten 48 percent of rapidly declining species and are driving species most quickly to extinction”. The enigmatic disappearances occur mostly in North and South America as well as in Australia and Puerto Rico and take place even within well protected and highly suitable areas such as the Yosemite National Park or Yellowstone National Park (Rincon, 2008). Hereby, the factors are multiple and yet not fully understood although disease and climate change and pollution are the most commonly sited sources. Figure 1 shows the geographical pattern of the dominant origins of fast decline in amphibian species, whereas figure 2 lists the habitat preferences and...
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