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Amphibian Decline

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Amphibian decline

Amphibian population has dramatically decreased in many different areas of the world. In the past twenty-five years we have been investigating possible causes for this decline. According to the published research there are factors that may contribute to the decline of amphibians such as habitat destruction, disease, and pesticide pollution.

Habitat destruction is a possible cause for amphibian decline; their decline is due in part to losing their breeding sites through intensive farming and road construction. Loss of their place to live and destruction of their habitat leaves them with no choice but to migrate and look for a place to live. By having such an industrialized world containing dangerous threats to the species such as, road traffic, lack of food, contaminated water, etc, will undoubtedly lead to amphibian decline.

Diseases are causing amphibian decline in some species as well as certain regions. According to Beebee and Griffiths, "Ribeiroia ondatraeis is a trematode worm that causes leg deformities in frogs." Eutrophication caused by human activities favors the growth of snails that provide the secondary host for this parasite. It is obvious that diseases can be lethal, and if humans keep altering the environment amphibians are going to encounter more diseases more often. In other words, we could be providing (consciously or unconsciously) the habitat the parasite needs to grow, which will end up in more leg deformities in frogs. Like Ribeiroia ondrateis, there are other harmful diseases that are also contributing to amphibian decline.

There are many types of environmental pollutants that could be causing the drastic declines of amphibian population. According to the article by Rick Relyea, pesticide pollution is a major reason for amphibian decline. Glyphosate, (commercially known as Roundup, Rodeo, and Aqua Master) could be the most detrimental of these. Glyphosate is generally used to control unwanted weeds in agriculture, forestry, aquatic habitats, and residential areas.

Rick Relyea conducted separate experiments for aquatic and terrestrial amphibians. He used outdoor pond mesocosms for the aquatic experiment with a factorial combination of herbicide treatment and soil treatments. A total of thirty experiments were divided into six treatments, each replicated five times. These units were separated into 1200-L cattle watering tanks, each filled with 1000-L of well water with a ph of 8. The tanks either received no soil, sand, or loam soil. Loam soil was not tested for pesticides; however no pesticides had been applied to it for several years. The amphibians used by Relyea were randomly chosen from a mixture of hatched egg masses. Three species of tadpoles were added to each tank; twenty leopard frogs, twenty American toads, and twenty tree frogs. Tadpoles were selected as newly deposited eggs from nearby ponds. All tadpoles were young, a sample of twenty tadpoles of each species were handled for twenty-four hours for survival reasons. The herbicide treatment (glyphosate, better known as Roundup) was applied two days after placing the tadpoles to the tanks. The amount applied was the same as the one likely to occur in natural wetlands; fifteen-mL of Roundup to each pesticide tank and fifteen-mL of well water to each control tank. Twenty days later the tanks were drained, and the tadpoles were removed, counted, and



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