|Nature Gallery (Global Trends)|
Wildlife & Habitat Destruction
|According to some scientists, plant
and animal species are becoming extinct
faster than at any time since the dinosaurs died out 65 million years ago
at the end of the Cretaceous period. As of 1990, 12 per cent of mammals
and 11 per cent of birds
worldwide were classified as endangered
or threatened. In the United
States alone, 540 species are endangered, and another 150 are
on the threatened list.
The loss of such biodiversity has many repercussions beyond the disappearance of individual species because of the broad variety of plants and animals required to sustain the natural cycles essential to human survival. For example, the interplay of freshwater plant and animal species keeps wetland ecosystems clean, and plants provide raw material for 25 per cent of the pharmaceuticals sold in the United States.
|Throughout history, the
primary cause of species extinction has been the introduction of
non-native species into new ecosystems. Imported farm animals, predators
brought in to control native pests, and accidental stowaways can severely
harm native flora and fauna
and upset ecological
equilibrium. This is particularly true on islands,
where species frequently evolved without competition from predators or
intruders. For instance, 75 per cent of all species in the United States
that have become extinct were native to the Hawaiian
Islands, where 3,900 exotic species have been introduced since
European explorers first arrived in 1778. Today, one-fifth of Hawaii's
native flora and 50 per cent of the state's indigenous
birds are endangered.
Habitat Loss and Poaching
loss is the second most critical factor in species
extinction. Worldwide, there is now 20 per cent less forest cover than
existed 300 years ago, and there is five times as much land devoted to
agriculture. Forests and fields
that are cleared for agriculture can sustain only a fraction of the
species they formerly held.
Poaching and hunting are another major cause of animal species extinction. In some regions of Africa, hunters in search of much-needed food have wiped out scores of game species. Poaching and illegal trade in animals are US$2 billion to $3 billion global industries, and as long as rhinoceros horns bring US$12,500 per pound on the black market and ocelot pelts fetch US$40,000, exotic animals will continue to be endangered.
In recent years, conservationists concluded that it is ineffective to try saving species one at a time. Most efforts to preserve biodiversity now focus on the maintenance of the habitat necessary for plant and animal survival rather than on particular species. Currently, 6 per cent of all the Earth’s land is protected or preserved habitat, although the preserves are not distributed equally across all continents. To that end, the World Conservation Union has set a goal of preserving 10 per cent of each of the Earth’s major ecological regions by the year 2000, thereby protecting greater numbers of species from extinction.