26) BIODIVERSITY
"It is often said that variety is the spice of life. No
intelligent investor confines his money to one or two shares. No
one can sit stably and comfortably on a chair with two legs. No
one remains fully healthy on a restricted diet. These facts are
obvious, but the larger analogy that a varied base is vital for
human existence fails to achieve recognition." - HRH Prince
Bernhard of the Netherlands
The variety of living things around us is one of the greatest
wonders of life on earth. Unfortunately this variety is being
steadily reduced by the actions of people. This has serious
consequences for the future.
Biodiversity describes the variety of life in an area, including
the number of different species, the genetic wealth within each
species, the interrelationships between them, and the natural
areas where they occur.
MASS EXTINCTION
Remarkably, we do not know the true number of species on earth.
More than 1,4 million have been identified, and it is estimated
that the absolute number is between 5 and 30 million! Human
destruction of the natural world is so serious that millions of
these species are doomed to become extinct before they have even
been named.
The biodiversity found on earth is the result of 3,6 billion
years of evolution. A natural part of the evolutionary process
is extinction, where species disappear owing to changes in their
living conditions which they are unable to survive. In recent
times, however, the rate of extinction has increased dramatically
and is estimated to be 1000 to 10 000 times greater than before
human intervention.
LOSS OF BIODIVERSITY - THE CAUSES
* Habitat loss:
All plants and animals rely on their habitat (the area where they
live), for food, water, shelter and living space. Growing human
populations requiring land for agricultural, industrial and urban
development are destroying species' habitat on a huge scale.
* Pollution:
Various forms of pollution contribute to the loss of plants and
animals. For example, marine turtles often mistake plastic bags
floating in the sea for jelly fish, and eat them. This may choke
turtles to death or prevent them from eating properly. Scavenging
birds are vulnerable to poison baits put out by farmers in an
attempt to control stock predators.
* Wildlife trade:
The huge international trade in wildlife threatens many species
with extinction. Despite laws passed to protect threatened
species, potential profits make illegal dealing worth the risk.
For example, the rhino is hunted for its horn which is prized in
Eastern countries as a dagger handle and for supposed medicinal
properties.
Cycads and many succulent plants are also traded illegally,
whilst many parrot species are collected for the wild bird trade.
* Alien species:
When an alien species is introduced to an area it may have
advantages which allow it to survive better than indigenous
species, and thus may threaten these local species with
extinction. Cape fynbos, for example, is threatened by Australian
acacias which were originally brought in to stabilise the dunes.
Alien species sometimes interbreed with indigenous species, as
has happened with the domestic cat and the African wild cat.
* Poaching and hunting:
This is often, but not always, linked to trade in a particular
species. The African wild dog, for example, has been in conflict
with stock farmers for a long time and has been hunted
relentlessly, making it Africa's most threatened carnivore.
THE IMPORTANCE OF BIODIVERSITY
Possibly the most important reason for the maintenance of
biodiversity is summed up by American conservationist, Aldo
Leopold: "The first rule of intelligent tinkering is to save all
the parts."
The variety of life on earth forms a huge gene pool which is the
material on which natural selection works in the ongoing process
of evolution, which generates more biodiversity. This gene pool
is also a resource of crucial importance to humanity for food,
fuel, clothing, shelter, and to maintain our health. Biodiversity
enhances our lives in countless ways, from the development of new
and improved food crops and medicines, to the sight of a flight
of geese against a sunset. While modern technology has given
people greatly increased power over nature, it has done little
to reduce our dependence on biodiversity.
Living things do not exist independently of each other, or the
non-living environment. They depend on one another in a variety
of ways: think, for example, of a food chain. Together with the
non-living parts of our environment (e.g. soil, water, air),
living things form essential life-support systems such as the
water cycle, the carbon cycle and several other nutrient cycles.
The pool of life is therefore much more than the sum of its
parts.
WHAT YOU CAN DO
* Demands for goods and services place pressure on the
environment - the less we use, the less severe the pressure.
* When a conservation issue rears its head, make your voice
heard - draw up a petition, contact your local MP, write to the
Department of Environment Affairs and liaise with your newspaper.
* Become informed and talk about this issue to your friends,
family and colleagues.
* Support a conservation organisation.
Many people believe that every species has the right to exist,
and that our role as custodians of the planet is to ensure their
survival.
DID YOU KNOW?
* Tropical rain forests are the world's most important areas of
species diversity, containing over half the world's species on
just 7% of the earth's land surface. They are being destroyed so
rapidly that most will disappear within the next century.
FURTHER READING
SOUTH AFRICA'S THREATENED WILDLIFE.
J. Ledger. Endangered Wildlife Trust, Johannesburg, 1990.
THE GAIA ATLAS OF PLANET MANAGEMENT.
N. Myers (ed). Pan Books, London, 1985.
GOING GREEN: PEOPLE, POLITICS AND ENVIRONMENT IN SOUTH AFRICA.
J. Cock and E. Koch (eds). Oxford University Press, Oxford, 1991.
SOUTH AFRICAN ENVIRONMENTS INTO THE 21ST CENTURY.
B. Huntley, R. Siegfried and C. Sunter. Human, Rousseau and
Tafelberg, Cape Town, 1989.
BIODIVERSITY.
E. Wilson (ed). National Academy Press, Washington D.C., 1988.
BIOLOGICAL DIVERSITY.
A pamphlet available from WWF-SA. Address below.
Enviro-Facts: "Why Conserve?" and "Biodiversity in South Africa".
USEFUL ADDRESSES
Department of Environment Affairs and Tourism.
P/Bag X 447, Pretoria, 0001. Tel. 012-310 3425.
WWF-SA.
P.O. Box 456, Stellenbosch, 7600. Tel. 021-887 2801.
Endangered Wildlife Trust.
P/Bag X11, Parkview, 2122. Tel. 011-486 1102.
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