HAMILTON SPECTATOR (Ontario) 29 August 03 Fearing for a world without frogs (Mark Coakley)
In the shallow water of a stream or swamp or pond, a baby frog wriggles out of its egg.
It is now a little tadpole, with no legs, and a tail for swimming. It breathes water and eats plants. When it grows to a certain size, the baby frog loses its tail and grows legs. Its eyes and mouth get much bigger. It starts to breathe air. The frog hops out of the water and starts hunting insects.
Adult frogs mainly eat bugs, catching them with a lightning-fast jab of the tongue. Ontario's frogs eat huge amounts of mosquitoes every summer (protecting us from diseases like West Nile). Ontario's frogs also eat a lot of annoying blackflies, deer flies, horseflies and houseflies.
In summer, female frogs start looking for love. Mr. Right is a male frog with a loud singing-voice and some real estate. (A sense of humour is also nice.) A female frog lays her transparent, jelly-like eggs in the shallow water of a stream or swamp or pond. A male fertilizes the eggs and they float on the surface, another generation of these strange, beautiful animals.
Frogs can live almost everywhere in the world -- including deserts, mountains and a part of the Arctic. There are many different kinds: navy-blue frogs, lemon-yellow frogs, fire-engine-red frogs. There are frogs smaller than a dime, and frogs bigger than a large house-cat. One kind of frog can bark like a dog. Another can puff its body up like a balloon, to frighten snakes.
To survive winter in Ontario, some frogs dig into the mud under a pond or stream, absorbing oxygen through their skin; other frogs spend winter on land, sleeping under dead leaves.
Breeding frog populations live in many of our natural places, especially Cootes Paradise and the Red Hill Creek valley and parts of the escarpment.
Eating mosquitoes and flies, providing food for fish and birds, fascinating kids and nature-lovers, frogs really are our friends.
And they are disappearing fast.
According to recent scientific reports, the world's frog population is shrinking. In the past few decades, frog populations in parts of North America, Central America, South America, Europe and Australia have rapidly declined, sometimes by as much as 15 per cent a year. Frogs are disappearing from streams and swamps and ponds all over the world. More than 20 frog species have become extinct in the past decade.
The Hamilton area is home to eight frog species. In recent years, the populations of the leopard frog, the bull frog and the chorus frog have declined in Ontario. The green frog, the tree frog, the wood frog, the pickerel frog and the spring peeper are also at risk. Why are frogs disappearing around the world?
One important factor is habitat loss. When wetlands are covered with buildings and lawns and shopping malls and parking lots, frogs go somewhere else. If there is nowhere else to go, they die. Roads and expressways cut frog habitat into fragmented, isolated chunks. Millions of frogs are killed in Ontario each year by cars while crossing roads to get to their breeding-places. Frogs live on small, shrinking islands of nature in a deadly ocean of concrete.
Habitat loss is a serious problem, but it does not explain why, in some places, a particular species of frog will decline or disappear, while another species in the same place does well. And frog populations have declined in provincial parks where their habitat is protected. Why?
Scientists disagree about what, other than habitat loss, is killing off the world's frogs. Some scientists blame increased UV radiation, from the thinning ozone layer. UV radiation has been linked to birth defects and vision problems in frogs. Other scientists point to global warming, or the stocking of lakes with non-native sport fish, or new kinds of parasites and disease.
All of those factors probably contribute to the frog declines, but the most important factor (combined with habitat loss) is probably pollution.
We release millions of different chemicals into nature, in huge amounts. They are easily absorbed by a frog's wet skin, or its tender floating eggs.
PCBs, dioxins and other chlorine chemicals build up in a frog's body, causing tumors or birth defects. Heavy metals, like mercury, weaken a frog's immune system. Other chemicals can disrupt frog hormones.
One of the most widespread pollutants is nitrate. Nitrate is released by beef and pork farming, sewage-treatment plants and the use of fertilizers. Approximately 20 per cent of the water around the Great Lakes has levels of nitrate that cause birth defects in frogs, and 3 per cent has nitrate at levels that kill frogs.
The most harmful kinds of pollution to frogs are probably pesticides -- sophisticated chemicals designed to destroy life. Over 3,000 pesticides are for sale in Ontario, with thousands of ingredients in unpredictable combinations. Only a few of these ingredients have been tested for effects on people. Even fewer have been tested for effects on wildlife. Ontario's golf courses, farms and lawn owners dump out huge amounts of toxic pesticides every year.
And it's getting worse.
Reacting to a recent panic over West Nile, Hamilton's top health officer has stated that she will "probably" send spray trucks to cover neighbourhoods with thick clouds of malathion -- which kills adult mosquitoes in air. Local government has already dumped 50,000 storm sewers in Hamilton (plus 35,000 storm sewers in Halton) with methoprene -- which kills young mosquitoes in water.
Malathion and methoprene hurt more than mosquitoes.
Malathion damages DNA, leading to birth defects in frogs. Malathion also disrupts the hormone systems of frogs. Exposure to malathion can cause nerve damage and asthma in people; it probably has a similar effect on frogs.
According to the Canadian Cancer Society, malathion spraying is "the least effective means of mosquito control and potentially the most risky in terms of human and ecosystem effects."
Like malathion, methoprene disrupts hormones.
In a laboratory experiment, frog eggs were exposed to methoprene. The frogs that hatched grew up with much higher than normal rates of mutations and early deaths.
Another experiment showed that in ponds dumped with methoprene, an average of 15 per cent of the frogs developed deformities such as extra legs. In ponds not dumped with methoprene, scientists found deformities on less than 1 per cent of the frogs.
Chemicals like methoprene and malathion are, together with habitat loss, taking us towards a world without frogs. Do we want that?
A world without frogs would be a world full of mosquitoes and biting flies. A world without frogs would be a world with fewer fish and birds, which rely on frogs for food. A world without frogs would be a world without their songs on a warm summer night.
A world without frogs would be a world much less strange and much less wild and much less beautiful than the world now in our hands.