There is marked decline in the population of amphibians in many parts of the world. Numerous possible causes have been put forward, including, climate change, habitat loss, habitat change, irradiation by UV-B, and acid precipitation. Of these, climate change has been shown to be the major cause.
There is growing evidence of declining population of amphibians and most this evidence is coming from area such as national parks, designated wilderness which are considered to be relatively pristine regions. Climatic change is the main suspect and may indirectly or directly be responsible for this decrease. Extirpations and extinction of golden toads and Harlequin frogs in Costa Rica and California’s Yellow legged Toads is the current study or inquiry subject in relation to the role played by climate changes in Amphibian decline. According to Collins and Crump (2009) one study has indicated an indirect role played by climate change, where the study shows that climate changes has provided optimum conditions for illnesses such as chytridiomycosis, therefore indirectly resulting in the decline and extinction of amphibians. But another provided opposing views by indicating that the spread of this medical condition and the extinction of the associated species do need a climate change to account for the spread and emergence of the medical condition. Due to the high sensitivity of amphibians to climate changes relative to other species, climate change may play a more direct role in their decline. Due to their biphasic life cycles, permeable skin, and unshelled eggs, these organisms have extremely high sensitive to even very small alteration in moisture and temperature levels.
The Breeding Phenology of amphibians and climate change (global warming).
Environmental parameters such as moisture and temperature play a vital role determining the period for amphibian breeding. Due to this, global warming may have a direct impact on the phenology of their breeding. Temperate region amphibians may have high degree of susceptibility to rising levels of temperatures. Majority of temperate species of amphibians spend of their entire inert, hiding from hot summers or extreme cold winters. Slight rise in moisture or temperature make them come out of their hibercula. Immediately they come out of their hiberculas, these amphibians migrate into stream and ponds for breeding purposes. Thus, it is hypothesized that one of the climate change’s direct role in amphibian population decline is related to the tendency of earlier breeding due to the increase in average temperature levels. If these temperate amphibians undertake their breeding too earlier than usual, the risk or vulnerability to a little bit snow melt triggered floods and freezes that are common earlier in the season relative to later times in the season. Some of the amphibians that have been shown to be undergoing earlier breeding include Ithaca New York’s Spring peeper, which has been shown to be currently undergoing earlier breeding relative to 1900. Others are smooth newt, grey tree frog, great-crested newt etc (Collins and Crump, 2009).
Climate changes may play an indirect role in the decline in the population of amphibians through very complex mechanisms. For example environmental changes in an organism’s locality may result in the decrease of an organisms’ immune system resulting in the increased in the risk of pathogen infection. This may lead to morbidity outbreaks resulting in high levels of mortality. In some cases climatic changes may provide optimum temperature conditions for the growth of certain pathogenic organisms. A good example of such pathogenic organisms is the Batrachochytrium dendrobaditidis commonly referred to as chytrid fungus whose optimum temperature has been shown to be 6 to 28degree centigrade and degenerates at 32 degree centigrade. According to Wells (2007) recent research by Gervasi in 2008 indicated a decrease in the number of white blood cells in the amphibians resulting in the weakening in the amphibians’ immunity due to increased pond desiccation. There is also evidence indicating that climate changes have resulted high levels of mist during the day and increased temperature levels during the night in the island of Costa Rica. This has provided optimum growth condition for B. dendrobatidis (Hassan, 2009).
The causes of the decline of amphibians are many but climate change has been shown to play a vital role either directly or indirectly. Hence any effort to reverse this trend should primary focus on global warming.