ВалерияГрузд

22.12.2022 06:41 •  Английский язык

When was the last time you saw a frog? Chances are, if you live in a city, you have not see

none for some time. Even in wet areas once teeming with frogs and toads, it is becoming less and

less easy to find those slimy, hopping and sometimes poisonous members of the animal kingdom.

All over the world, even in remote jungles on the far side of the globe, frogs are losing the

ecological battle for survival, and biologists are at a loss to explain their demise. Are amphibians

simply over-sensitive to changes in the ecosystem? Could their rapid decline in numbers be

signalling some coming environmental disaster for us all?

This frightening scenario is in part the consequence of a dramatic increase over the last

quarter century in the development of once natural areas of wet marshland; home not only to

frogs but to all manner of wildlife. Yet, there are no obvious reasons why certain frog species are

disappearing from rainforests in the Southern Hemisphere which are barely touched by human

hand. The mystery is unsettling to say the least, for it is known that amphibian species are

extremely sensitive to environmental variations in temperature and moisture levels. The danger is

that planet Earth might not only lose a vital link in the ecological food chain (frogs keep

populations of otherwise pestilent insects at manage able levels), but we might be increasing our

output of air pollutants to levels that may have already become irreversible. Frogs could be

inadvertently warning us of a catastrophe.

An example of a bizarre occurrence regarding a species of frog dates from the summer of

1995, when ' an explosion' of multi-coloured frogs of the species Rana kleptonesculenta occurred

in the Netherlands. Normally these frogs are brown and greenish-brown, but some unknown

contributory factor is turning these frogs yellow and/or orange. Nonetheless, so far, the unusual

bi- and even tri-coloured frogs are functioning similarly to their normal-skinned contemporaries.

It is thought that frogs with lighter coloured skins might be more likely to survive in an

increasingly warm climate due to global warming.

One theory put forward to explain extinct amphibian species that seems to fit the facts

concerns the depletion of the ozone layer, a well-documented phenomenon which has led to a

sharp increase in ultraviolet radiation levels. The ozone layer is meant to shield the Earth from

UV rays, but increased radiation may be having a greater effect upon frog populations than

previously believed. Another theory is that worldwide temperature increases are upsetting the

breeding cycles of frogs.