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Outline I. Introduction Thesis Statement: Is the amphibian disappearances or deformities an early warning of serious environmental problems? II. Origins a. Early b. Evidence III.
Habitat a. Ecosystem IV. Indicator a. Detection V.
Disappearance a. Arizona VI. Why? a. Diseases b. Pollution VII.
Frogs a. Endangered b. Threatened VIII. Conclusion Disappearance of Frogs Amphibian populations are declining or are disappearing around the world.
Scientists are impetuously searching for clues as to why there is a decline in our frog species. In existence for over 350 million years, frogs have survived through the age of the dinosaurs and through the mass extinction of those dinosaurs. Why now, are the populations of a unique, colorful species declining in rapid numbers? Some scientists believe that ultraviolet radiation is the cause. Others are blaming the toxic substances so easily discarded every day by large companies. Scientists have found that many deadly virus infections and a chytrid fungus are the cause of die offs.
Amphibians have been in existence for over 350 million years. They were once fish, aquatic dwelling animals, and were the first vertebrates to evolve from water to land. Amphibians survived both the dinosaur age and the mass extinction of the dinosaurs. According to Neil Shubin of the University of Pennsylvania, there is evidence of frogs living in the Jurassic period around 200 million years ago. A fossilized skeleton dug up in 1982 in Arizona, was found in a layer of rock known to be from the Jurassic period. Wetlands are their primary breeding habitat, but forests are where they spend most of their non-breeding season.
Amphibians have an ecological importance in both fresh water and terrestrial habitats. They are both predators and prey, and constitute great biomass. The role of the amphibians on wetlands or terrestrial ecosystems is not clearly defined; however, ecologists are investigating their significance in the environment. Since frogs breathe either partially or wholly through their skin, they are considered an indicator that the ecological balance is changing. They are exposed to the environment completely all the time and are more vulnerable than a human, detecting changes in the environment before any human has any indication of what is happening.
Other factors making them a prime indicator is the fact that they dwell both in water and on land and they store contaminates, causing a high concentration of toxins to be found in their fatty tissues. This concentration can be found and analyzed by scientists to prove that the environment is full of toxic wastes, and that it is affecting the animals. Frogs are a higher order species and if what it eats has eaten something with contaminates or toxins, the frog will also have contaminates or toxins in its system. Our frogs around the world are disappearing. Those disappearances and deformities found in some of the frog species can be considered an early warning that the environment is declining or of ecological imbalances. Out of five species of frogs in Arizona and New Mexico, four of those species have hit critical status.
These low populations are due to non-native invaders of bullfrogs, crayfish, and predatory fishes. Arizona's Game and Fish Department stocked ponds and artificial lakes with non-native bass, trout, and bullfrogs, to promote sport fishing. The bullfrogs proved not only to be competitors with the other frogs but they eat the native leopard frogs. This is occurring in the same region where the Vegas Valley Leopard Frog became extinct in 1966. According to scientists many deadly virus infections and a chytrid fungus has been identified as causes for the die-offs. Scientists are also investigating the effects that ultraviolet radiation, due to depletion of the ozone layer, non-native predators, contaminants from toxins, and rising temperatures.
Other factors may be involved such as, habitat destruction by timber companies who viscously cut out forests or by the agricultural companies, who rip out the trees and fill in the wetlands so many frogs depend on for breeding. They believe that there is not just one factor involved in the declines, but several contributing factors. The virus and the fungus has been around for years, consequently, the radiation, acid rain, and contaminates may have weakened the frogs ability to fight the infection or fungus. Frogs listed as endangered are few; however, when we take a step back and look at the whole world the declining amphibian populations are astounding. The Palestinian Painted Frog became extinct in Israel in 1956. Endangered frogs include, but are not limited to the Israel Painted Frog, Panamanian Golden Frog, Stephen Island Frog, and many others.
Threatened are the Goliath Frog in Africa due to habitat loss, the Leopard frog in Arizona and New Mexico, the western toad in the Rocky Mountains, and the tailed frog in the Pacific Northwest. Before we can eradicate the problem of the amphibian decline, we must first determine what the ideal, quality habitat would be. To promote healthy and diverse amphibian populations we must be able to restore or retain critical habitats. The fact remains that due to man being here, cutting forests, filling in wetlands, or polluting the world, the animals are suffering. Whether it is earthworms, frogs or elephants is irrelevant. Something has to be done.
The disappearance of the frogs may be part of a cycle like the distinction of the dinosaurs. Now, we have a mass distinction of the frogs. However, from a scientific point of view, it can be the warning of a dying earth. Works Cited Johnson, George B. The Living World. Missouri: WCB-McGraw-Hill, 1997: pp. 366 - 367.
Amphibians, United States Geological Survey web Amphibians declining since 1960 s, USA Today, May 2000. Amphibian Facts, Center for Global Environmental Education, web Faye Flam, Jurassic frogs, The Franklin Institute, web Focus on Amphibian Declines and Deformities, Frogweb, web Goliath Frog, American Museum of Natural History, web Habitat, web frame 1. htm. Muro, Mark, Western Roundup, High Country News.
May 25, 1998. Vol. 30, No. 10
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