问答题 The world's tropical rainforests comprise some 6% of the Earth's land area and contain more than half of all known life forms, or a conservative estimate of about 30 million species of plants and animals. 61)Some experts estimate there could be two or even three times as many species hidden within these complex and fast- disappearing ecosystems — scientists will probably never know for certain so vast is the amount of study required Time is running out for biological research. 62)Commercial development is responsible for the loss of about 17 million hectares of virgin rainforest each year — a figure approximating 1% of what remains of the world's rainforests.
The current devastation of once impenetrable rainforest is of particular concern because, although new tree growth may in time repopulate felled areas, the biologically diverse storehouse of flora and fauna is gone forever. 63)Losing this bountiful inheritance, which took millions of years to reach its present highly evolved state, would be an unparalleled act of human stupidity. Chemical compounds that might be extracted from yet- to-be-discovered species hidden beneath the tree canopy could assist in the treatment of disease or help to control fertility. Conservationists point out that important medical discoveries have already been made from material found in tropical rainforests. The drug aspirin, now synthesised, was originally found in the bark of a rain- forest tree. Two of the most potent anti-cancer drugs derive from the rosy periwinkle discovered in the 1950s in the tropical rainforests of Madagascar.
The rewards of discovery are potentially enormous, yet the outlook is bleak. Timber-rich countries mired in debt view potential financial gain decades into the future as less attractive than short-term profit from logging. Cataloguing species and analysing newly-found substances takes time and money, both of which are in short supply. The developed world takes every opportunity to lecture countries which arc the guardians of rainforests. 64)Rich nations exhort them to preserve and care for what is left, ignoring the fact that their wealth was in large part due-to the exploitation of their own natural world.
It is often forgotten that forests once covered most of Europe. Large tracts of forest were destroyed over the centuries for the same reason that the remaining rainforests are now being felled—timber. 65)As well as providing material for housing, it enabled wealthy nations to build large navies and shipping fleets with which to continue their. Plunder of the world's resources. Besides, it is not clear that developing countries would necessarily benefit financially from extended bioprospecting of their rainforests. Pharmaceutical companies make huge profits from the sale of drugs with little return to the country in which an original discovery was made.