An Early Indicator of Global Disaster
Frog populations around the world have showed increasing signs of stress in recent years. Some species have disappeared, and others are no longer found where they used to be. An increase in deformities may be a sign that something is wrong.
The continental United States is home to at least 230 amphibian species: 90 frog and toad species, and 140 species of salamanders.
In the U.S., declines are particularly serious in California, the Rocky Mountains, the Southwest, and Puerto Rico. Worldwide, decline "hot spots" also include Australia and Central America.
Amphibian deformities - extra limbs, malformed or missing limbs, and facial malformations - have been documented in 44 states, and involve nearly 60 species. In some local populations, up to 60% of the amphibians exhibit deformities.
Source: USGS
Possible Reasons For The Declines
An increase in ionizing radiation (UV-B) resulting from ozone layer depletion.
Chemical contamination: the oestrogenic effects of pesticides, acid precipitation, or the effects of fertilizers and herbicides.
Introduction of exotic competitors and predators
Herpetologists (scientists who study amphibians and reptiles) have reported finding frogs with missing legs, extra legs, misshapen legs, paralyzed legs that stuck out from the body at odd places, legs that were webbed together with extra skin, legs that were fused to the body, and legs that split into two half-way down. They have also found frogs with missing eyes. One one-eyed frog had a second eye growing inside its throat.
Amphibians are good "indicators" of significant environmental changes that may go initially undetected by humans. Humans breathe through lungs, which are inside our bodies and thus protected from direct contact with air and water. Amphibians, however, breathe partially (and in some species, completely), through their skin, which is constantly exposed to the environment. Their bodies are much more vulnerable and sensitive to factors such as disease, pollution, toxic chemicals, radiation, and habitat destruction. The worldwide occurrences of amphibian declines and deformities could be an early warning to us of serious ecosystem imbalances.
The current global loss of species is a process generated by the activities of humans. As we modify our environment for our own ends, it is clear that the destruction of the habitats of other species leads directly to their disappearance. However, more recently we have begun to observe, and to speculate about more subtle impacts that human activities may be having, acting at a global level.
We have depleted atmospheric ozone levels; pollutants are accumulating in the natural systems on which we and other organisms depend; we may be altering weather patterns. Such gradual, but fundamental changes are certain to have an effect on the ecosystem. It is possible that amphibians are responding adversely to these changes. They may be showing us how our activities are affecting our shared ecosystem.
The world's frogs, toads and newts and other amphibians are dying out, with populations falling each year, according to research.
One of the biggest studies of its kind reveals that amphibian numbers have declined dramatically over the past 40 years. The findings were compiled using Internet contacts with some 200 scientists around the world. Pollution, intensive farming, disease and climate change are all likely to have played a role said Jeff Houlahan, a PhD candidate in biology from the University of Ottawa in Ontario, Canada who spearheaded the report. Data on 936 populations of amphibians and 157 species came in from 37 countries and eight regions of the world.
Using data covering the last four decades, the analysis concluded the world's amphibian population has likely decreased by more than 50 per cent since the 1950s.
Decline was steepest in the 1960s -- as much as 15 per cent a year -- but continued at a slower rate, roughly two per cent, in the 1980s and '90s. North America has shown the greatest fall in amphibian populations in recent years.
Berkeley – The nation's top-selling weed killer, atrazine, disrupts the sexual development of frogs.
