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Amphibian Population Declines Amphibian Population Declines An unparalleled diminishment in populations is occurring worldwide in many species of amphibians frogs, toads, and salamanders.
Although there are various causes for declining amphibian populations, the most obvious is habitat destruction. However, introduced exotic species, pathogenspollution, and global environmental changes all contribute. Moreover, various factors can act together to produce adverse effects on amphibians.
Because amphibians are important predators and prey in many ecosystemsdeclines in their populations may affect many other species that live within the same ecological community.
For example, populations of aquatic insects and amphibian predators such as snakes, birds, mammals, and fish may be especially affected by a loss in amphibians. Moreover, the populations of animals that amphibians eat, such as mosquitoes, may increase as amphibians disappear.
Water Quality Factors Amphibians have permeable, exposed skin and eggs that may readily absorb toxic substances from the environment. Their eggs are laid in water or in moist areas, and their larvae tadpoles are aquatic.
Because amphibians are intimately tied to an aquatic environment, the quality of the water in which they live can affect their growth, development, and survival. Because pollutants, waterborne pathogens, and global environmental changes can all affect water quality, these factors can in turn affect amphibians.
Conversely, amphibians are important indicators of water quality, and are considered a sentinel species, meaning that what affects amphibians presently may affect other animal species in the future.
A number of studies have shown that acidification of fresh water that is, a reduction in pH to acidic levels via acid rain, acid snowmelt, or other modes of pollution are harmful to amphibian growth and development.
Some species are more tolerant of acid conditions than others. Thus, depending on the species, the amount of acidity, and other environmental variables, amphibians may experience developmental deformities and increased mortality due to acidification. Acidification can potentially affect amphibian populations and the communities in which amphibians live.
For example, some populations of toads in Britain have probably been reduced by water acidification. Salamander populations in Colorado seem to have declined because of increased acidification during snowmelt.
Several studies have shown that acidification of the water can affect competition and predation between amphibians. Thus, the larvae of some frog species may have increased survival rates under acid conditions because their salamander predators show reduced predation at low pH. Many chemical products used in agriculture and industry pollute aquatic habitats, causing potentially severe damage to ecosystems.
For example, the increase in concentration of nitrate in surface water on agricultural land due to numerous sources may be hazardous to many species of fish, wildlife, and even humans. Data suggest that nitrogen-based fertilizers may be contributing to amphibian population declines in agricultural areas.
However, some species appear to be more sensitive than others to nitrate and nitrite pollution. In one experimental study in Oregon, it was shown that some species reduced their feeding activity, swam less vigorously, and showed disequilibrium when nitrate or nitrite ions were added to the water.
Importantly, all species tested in this study showed high mortality at nitrite levels deemed safe for warm-water fishes by the U. Furthermore, significant larval mortality occurred at the recommended limits of nitrite concentration for drinking water.
Just as amphibian species display variation in sensitivity to nitrate-related compounds, they also show variation in tolerance to other toxic substances that may be found in water.
Insecticides such as organophosphates, carbamates, and synthetic pyrethroids, which are used mainly in crop production, have a wide array of effects on amphibians. Depending on the concentrations used and the species involved, some of these substances may be lethal, may affect growth and development, or may affect metamorphosis.
Effects of Ultraviolet Radiation Global environmental changes may also affect amphibians. For example, ambient natural but increasing levels of ultraviolet UV radiation owing Scientists believe that certain compounds found in agricultural fertilizers, pesticides, and herbicides are contributing to the decline of many amphibian populations in the United States and other countries with large-scale, chemically enhanced agriculture.
Yet synthetic chemicals are only one among several human and environmental factors linked to amphibian impacts.Batrachochytrium dendrobatidis (Bd), the causative agent of chytridiomycosis, has been implicated in widespread amphibian declines and is currently the largest infectious disease threat to biodiversity.
Here, we review the causes of Bd emergence, its impact on amphibian populations and the ecology of Bd transmission.
Amphibians. If amphibian decline is well-documented in many parts of the world, the role of EDCs (particularly pesticides, including atrazine) in this decline is still a topic of discussion (Gubbins et al., in Amiard-Triquet et al., ).
For intersex, the lack of full scientific certainty likely results from the general plasticity of amphibians with regard to . Amphibian declines are most dramatic in tropical regions of the world, where amphibian diversity is higher and human economic development is occurring fastest.
Britain is, however, experiencing amphibian declines that mirror what is . Amphibian declines may be an early indicator of the Hocking and Babbitt.—Amphibian Contributions to Ecosystem Services.
2 products including food, fresh water, fiber, genetic resources, and medicine. Regulating services include consumption can be extremely detrimental to amphibian populations. Most amphibians . Dramatic declines in amphibian populations, including population crashes and mass localized extinction, have been noted since the s from locations all over the world, and amphibian declines are thus perceived as one of .
Amphibian declines may be an early indicator of the Hocking and Babbitt.—Amphibian Contributions to Ecosystem Services. 2 products including food, fresh water, fiber, genetic resources, and medicine. Regulating services include consumption can be extremely detrimental to amphibian populations.
Most amphibians sold for consumption are.