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5. Biodiversity and genetic resources:

When we think of wildlife facing extinction, we are usually thinking of large majestic animals such as whales, elephants and rhinos or of the “cuddly” black-and-white panda. These creatures are indeed at risk of extinction because of irresponsible and cruel hunting by human predators. It is easy to become angry at the plight of these endearing mammals. But the threat of extinction is not limited to the few species that we can recognize in pictures or visit in zoos. The threat of extinction affects almost every species on earth, down to the tiniest microbe.

A species is

a group of animals, plants or microorganisms that share a common genetic structure. Members of a species can mate with one another but not with members of another species. The earth probably contains between 10 and 100 million different species, although scientists have so far only identified 1.4 million of them. Each species is genetically unique. This means that we cannot produce new members of a species by breeding other species. The great variety of different species of animals, plants and microorganisms are the world’s genetic resources. There is a new word in the English language that underlines the importance of conserving these resources: biodiversity, which means biological diversity or, literally, “many different forms of life”. Fifty to seventy percent of all the earth’s animal, plant and bacteria species live in the tropical rainforests. The floor of the forest is a warm, moist, sheltered environment that encourages a great variety of living things to grow. Wild plants and animals in the rainforests already supply us with hundreds of useful materials, foods and medicines. The genetic resources within the rainforests provide a huge potential for new developments. We do not know very much about the balance of nature inside the rainforests. We cannot say that any single species is unimportant to the rest of the ecosystem. Maintaining biodiversity by conserving the rainforests is one of the greatest priorities for environmentalists today. Yet at the present rate of destruction, 7 percent of the earth’s biodiversity is lost every 25 years.

The balance of nature within any ecosystem depends on the complex interaction between millions of species of animals, plants and micro-organisms. The death of one species could threaten the survival of hundreds of others. A second species might lose its food supply and it, too, might become extinct. Another species could lose its predators, so it might become more numerous. The populations of parasites, arid microorganisms that depend on these larger specie will also change. This may lead to the spread of new, virulent disease in the higher organisms. The balance of nature is often a very precarious one. There are many more species of small organisms than of large ones. Insects outnumber all other animal species combined, and bacteria outnumber all the animal and plant species together. These small organisms have a large influence on the microenvironment.

Microorganisms influence important physical properties such as the acidity and mineral content of the soil, the salinity of the sea, and the amount of oxygen and carbon dioxide in the air. Changes in the populations of microorganisms may, therefore, cause major changes in the compositions of the earth and its atmosphere.

In general, organisms that live in the wild are stronger and more resistant to disease that domestic strains. They can replace domestic strains that develop disease. In the 1860, the grape vines in Europe were infested with a deadly pest, phylloxera, which threatened to destroy the entire European grape harvest. The wild American vines were resistant to phulloxera, so farmers cross-bred the European vines with these wild strains and the grape harvest survived. A more resent example of the benefits of biodiversity is a species of wild corn discovered a few years ago growing in a Mexican forest. The wild corn was extremely hardy and was resistant to viruses that often attack cultivated corn. The wild strain was a perennial (that is, it grew again spontaneously every year), whereas other forms of corn are annuals (that is, the farmers must sow new seeds every year). Scientists successfully cross-bred the wild strain with domestic varieties and created a new, hardy, perennial strain of cultivated corn. The wild Mexican corn was only growing in a tiny area of forest – about four hectares in total. When the corn was discovered, this small area was threatened by timber traders who were about to cut down the trees.