SCIENTISTS ARE SEARcHING FOR THE CAUSES oF AMPHIBIAN DECLINES meat Yet another t
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SCIENTISTS ARE SEARcHING FOR THE CAUSES oF AMPHIBIAN DECLINES meat Yet another threat is the invasion AuMutionisanother human-caused the scientists who of amphibian habitats by nonnative study frogs and other amphibians, threat to amphibians, Frogs and other have identified a number of factors- artan ssh species. Some of this immi tddesin ponds and in the bodies of both natural and gation natural but humans acciden- hreatem these species atvaious points insects that they eat. This can make uyor delberately transport many to bacterial in ther Efe goes. One of the natural them more vulnerable spedes to amphibian habitats. and fungal diseases and tosome causes Aarasiten such as fatworms Most herpetologists believe that a parasites. Amphibian epen and that feed on certain amphibian eggs. combination of these factors which Natonal Geographic Explorer Wone Scientists think this has caused birth vary from place to place, probably Hayes, a professor of biology at defects such as missing limbs or etra responstole for most of the decine and University of cassonia Bereiry is limbs in some amphibians. disappearances among amphbian conducting research on how some Some herpetologists hypothesize pesticides can harm frogs and other that vial and fungaldbeases espe- animals by disrupting their endocrine cially the dytid fungus (Figure 4B) critical Thinking that attacks the skin of togs, are re- on the factors lated above, which overhunting is another problem. es ducing the frogs' ablity to ingestewater three do you think could be most ef- pecialy in areas of Asia and Europe. through their skin. This leads to death lectively controlled by human efforts? where frogs are hunted for their leg from dehydration. Such diseases an spread fairly easily because adutsof many amphibian species congregate FIGURE 4B Frogs kned by the large numbers to breed. dytid fungus at a Another major threat to amphibians lake in CaMornia. is habitat kss and fragmentation. This is mostly a human caused problem re- sulting from the clearing of forests and the draining and of freshwater wetlands for farming and urban devel. opment. Another threat is prolonged drought, which can dry up breeding pools that frogs and other amphblans depend on for reproduction and sur- vival through their early stages of life (Figure 4O. Another human-influenced problem is higher leveb of Wadiation, which can harm embryos of amphibians in shallow ponds as well as adults bask- Wing in the sun for warmth. Hotoricaly such radation has been screened by ozone in the stratosphere, but during the past few decades, oaone-depleting chemicals released into the topo- sphere from human sources have drifted upward into the stratosphere FIGURE 4.c This golden toad and destroyed some of the protective lived in Costa Rcashighatitude onone found there Monteverde Cloud Fores Reserve. The species became extinct in 1989, apparenty because tshab- ital dried up.Explanation / Answer
Ans: Since frogs are the major predators of insects and plays an important role in the food chains. In the absence of frogs insects multiply out of control causing considerable damage to crops and a dramatic increase in insect borne diseases such as encephalitis and malaria. They act as an early warning system for the quality of the environment and the potential threats to other animals.
The three factors that can be most effectively controlled by human efforts includes:
1. With the ever increasing human population habitat destruction and fragmentation will become even more usual. Forestry and agriculture take a major toll on frog populations. It has also been demonstrated that roads and agricultural fields are significant barriers to terrestrial arthropods and small mammals and this is also true for amphibians. Since amphibians normally requires aquatic and terrestrial habitats to survive and the threats to either habitat can affect populations. Hence, amphibians may be more vulnerable to habitat modification than organisms that only require one habitat type. Large scale climate changes may further be modifying aquatic habitats, preventing amphibians from spawning altogether. Thus amphibian population can be enhanced by controlling the human activities which modifies or even destroys the natural habitate of amphibians.
2. Pollution and chemical contaminants: Acidification of natural habitate of frogs exerts a negative effect on the frogs’ population. Pollutants like Aluminium, cadmium, copper, zinc and iron are all toxic to amphibians. Organic herbicides and pesticides also cause a developmental abnormalities or fatalities in the amphibians. Herbicide like roundup is extremely toxic to tadpoles and adult frogs. The insecticides like DDT and Dieldrin are also harmful even at very low level.
3. Ozone depletion and ultraviolet radiation: Climatic changes present a serious threat to amphibians because it alteres the precipitation patterns and usually result in changes to wetland habitats. And also increases in UV-B radiation due to ozone depletion have been found to severely impact some amphibian species.
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