Monday, September 1, 2008

Frogs: Global Canaries

Frogs are considered to be the “canaries in the coal mine” of the environment. Before instruments were made that could detect lethal or explosive gases, coal miners used to take a canary in a cage down into the tunnels with them. Birds have very sensitive respiratory systems and respond to toxins and gases before humans even know there is a problem. If the canary collapsed, the men left the mine immediately and management then had to deal with the problem.

Frogs have a thin, permeable skin that is not waterproof making frogs and tadpoles sensitive creatures – a living barometer of the health of the environment. Due to the porous nature of the skin (all frogs breathe partially and some completely through the skin), they absorb chemicals from both the air and the water. With their skin constantly exposed to the environment, their bodies are much more vulnerable and sensitive to factors such as disease, pollution toxic chemical, radiation and habitat destruction.

Toads and frogs are part of the amphibian family. The word “amphibian” means “double life” in Greek. This refers to the two stages in every amphibian’s life – life in the water and on land. Frogs can be found everywhere on earth with the exception of the Arctic, Antarctic and Greenland. So, is it surprising that these changes are happening world-wide?

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.

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.

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.

Limited research findings and anecdotal information suggest several possible causes, for this decline including habitat loss; introduction of non-native predators such as fishes and bullfrogs; disease; and, possibly airborne contaminants. Where does this leave us? If we don’t change; we may be the last generation to hear frogs in the wild.

I grew up not many miles from where I live now. Thirty-five years ago, I was lulled to sleep every night by a chorus of frogs. I loved the sound and lay awake for hours just listening and imagining. Thirty-five years ago, was the last time I heard frogs in the wild. I haven’t heard a frog in 35 years unless it was on television. I, for one, miss them!

1 comment:

Kathi said...

You're coming up with some great topics, Philippa! We still have lots of frogs, including tree frogs, where I live in the Southern US. I was at a friends house on a local mountain the other night and the chorus of frogs was absolutely deafening. Of course, there are many changes in the flora and fauna here, from environment, etc. Reading your blog, given what is happening with the ice caps, I can't help but wonder if we would have had the blessing of the frogs warning sooner, if they were in the Artic. They're paying a horrible price for our stupidity and we, apparently, are still not listening.