Decline in amphibian populations
Since the 1980s, decreases in amphibian populations, including population decline and localized mass extinctions, have been observed in locations all over the world. This type of biodiversity loss is known as one of the most critical threats to global biodiversity. The possible causes include habitat destruction and modification, diseases, exploitation, pollution, pesticide use, introduced species, and ultraviolet-B radiation (UV-B). However, many of the causes of amphibian declines are still poorly understood, and the topic is currently a subject of ongoing research.
Modeling results found that the current extinction rate of amphibians could be 211 times greater than the background extinction rate. This estimate even goes up to 25,000–45,000 times if endangered species are also included in the computation.[1]
Scientists began observing reduced populations of several European amphibian species already in the 1950s. Nevertheless, awareness of the phenomenon as a global problem and its subsequent classification as a modern-day mass extinction only dates from the 1980s. By 1993, more than 500 species of frogs and salamanders on all five continents were in decline.
Symptoms of stressed populations[edit]
Amphibian populations in the beginning stages of decline often exhibit a number of signs, which may potentially be used to identify at-risk segments in conservation efforts. One such sign is developmental instability, which has been proven as evidence of environmental stress.[43] This environmental stress can potentially raise susceptibility to diseases such as chytridiomycosis, and thus lead to amphibian declines. In a study conducted in Queensland, Australia, for example, populations of two amphibian species, Litoria nannotis and Litoria genimaculata, were found to exhibit far greater levels of limb asymmetry in pre-decline years than in control years, the latter of which preceded die offs by an average of 16 years. Learning to identify such signals in the critical period before population declines occur might greatly improve conservation efforts.