Why Frog Populations Are Decreasing
Climate Change, Infections and Unsustainable Amphibian Trade
Jul 11, 2009
Scientists have warned for years that the worldwide disappearance of amphibians is an impending sign for ecological changes that imperil the natural world. The resilience of amphibians has been legendary; as a species they have survived for hundreds of millions of years. Now, these creatures, going through their sixth massive extinction, seem to be experiencing challenges that threaten not only the survival of the species, but that of the whole natural world. Three man-made factors stand out as reasons for this ecological disaster: global warming, infections and amphibian trade.
Climate Change and Global Warming
Climate change and global warming have created a set of conditions that are proving to be more than challenging to the amphibian population. Despite evidence that new species of frogs have been discovered recently, scientists are skeptical that amphibians are able to evolve quickly enough in the face of unprecedented changes in the environment. In fact, many suspect that the evolutionary advantages developed by the species over the years may prove to be disadvantageous to them under new climate conditions.
For example, amphibians lay eggs in shallow water under direct sunlight; while this proved to be an evolutionary advantage in the past, it has now become a hotbed for genetic mutations; the stronger UV-B radiation from the sun is producing genetic mutations, impaired immune systems and slower growth rates, hampering the “survivability” of new amphibian generations. Furthermore, fresh water ponds are no longer fresh because industrial pollutants and fertilizers have literally contaminated the water. Amphibian populations are therefore becoming more vulnerable to toxins and infections.
Climate Change and Infections
Global warming has accelerated daytime and night-time temperature changes that in essence have created a “perfect storm” for the gestation of a skin fungal infection that is particularly deadly for the amphibian population. According to J. Alan Pounds, principal scientist in a study on amphibian extinction affiliated with Tropical Science Center’s Monteverde Cloud Forest Preserve in Costa Rica, global warming conditions have enhanced the growth conditions of this fatal fungus.
Compounding the situation is the tendency of amphibians to lay eggs in communities; their tendency to congregate communally has once been a protective strategy against predators. However,this communal tendency is now contributing to faster and more effective spread of the fungus among amphibian populations. The fungus infects tadpoles which spread the spores to adults; scientists also know that these fungal spores can swim through water to infect frogs and other amphibians.
Unsustainable Amphibian Trade and the Ecosystem
A third major threat to the amphibian population is the unsustainable appetite for amphibian trade on the international markets. Statistics show that this appetite is voracious: anywhere from 200 million to more than a billion amphibians are consumed worldwide each year; in essence, “frogs are literally being eaten to extinction.” The United States and Europe have the highest demand for amphibians as food and pets. Asia, South America and Central America share a wide demand for amphibians for medicinal use. Trade is one of the chief factors in the spreading of the fatal skin fungus.
Amphibians are part of an ecosystem whose disruption bodes ill for human survival; is there hope that their resilience will see them through the next stage of evolution?
Oregon State University (2007, May 5). Amphibians In Losing Race With Environmental Change. ScienceDaily. Retrieved July 16, 2009, from sciencedaily releases/2007/05/070501075044.
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