Biodiversity - Page 3 - By Mara Hurwitt


Extinction Of Species
Although biodiversity is lost in many different ways, the most fundamental is the extinction of species. Once eliminated from the Earth, a species cannot be regained. Extinction is irreversible. Extinction is forever.

Species extinction is a natural phenomenon, and, theoretically, all species have a finite span of existence. However, man is now responsible for the extinction of species far in excess of any otherwise naturally occurring rate. Species are now being lost at a rate that rivals the mass extinctions of Earth history. This mass extinction is unique, in that it is the only one attributable to the actions of a single species - man.

Humans contribute to species extinction in many ways, including habitat destruction, modification, and degradation, as well as over-exploitation of species through over-hunting, fishing or collection.

The second or third most lucrative illegal international trade is the buying and selling of wildlife, which threatens the very survival of many plant and animal species. The Convention on International Trade in Endangered Species (CITES) restricts international commerce in products such as elephant ivory, rhinoceros horns, and sea turtle shells, as well as other items taken from plants or animals endangered by trade. Unfortunately, the total ban on trade in elephant ivory may be lifted in the near future to allow "limited" sales from animals who have died a natural death or otherwise come into the possession of national governments. However, since it is impossible to distinguish such ivory from that acquired by the killing of healthy wild elephants, this change in policy may bring back much of the elephant poaching that the worldwide ban has sought to end.

Clearcutting and burning result in the elimination of nearly 28,000 species annually. On the North American continent alone, 200 plant species and 71 species and sub-species of vertebrate animals have been lost in the last 500 years, and another 750 species are officially recognized as endangered or threatened. Approxmately 20% of plant species are in danger of significant reduction or even extinction in the northeastern United States, and much of the rest of the country is facing similar losses.

Increasing demands on limited biological resources can only cause the rate of extinction to accelerate. Many specialists in biological diversity estimate that the current rate of habitat destruction will cause a full 25% of all species to fall victim to premature extinction within the next 30 years.

In the 5.5 billion years of Earth's existence, there have been five mass extinctions recorded in the fossil record. These episodes all took place during the last 500 million years, when large complex organisms have populated the land and oceans, at intervals of between 20 and 140 million years. The most recent, which occurred about 65 million years ago at the close of the Mesozoic Era, has been attributed to some cataclysmic physical event - a giant meteor strike or unusually active volcanoes. This last major extinction brought the Age of Dinosaurs to an end, and another 5 million years passed before the Earth regained its previous degree of biological diversity through evolutionary processes.

Scientists believe we are now threatened with the greatest mass extinction in 65 million years. Even the most conservative scientific estimate of the current global extinction rate warns that half of all living species could be eliminated within a mere century. If the current rate of species extinction continues unabated, the Earth could experience a crisis of the magnitude of the Permian crash that wiped out 77% to 96% of all marine animal species 240 million years ago. Of particular concern, plant species which survived the last mass extinction largely intact are now disappearing at an unprecedented pace, with as yet untold consequences for the future of life on Earth.
Value Of Biodiversity
Although it is difficult to predict the ultimate consequences of the loss of biodiversity, we can easily identify many of the benefits offered by diversity.

Biological diversity is essential to maintaining the biosphere functions that support life on Earth. Diverse ecosystems provide alternate pathways for critical ecological processes, ensuring that the ecosystem can continue normal functions despite the loss or degradation of a single mechanism.

The life processes and interactions of the organisms comprising ecosystems control the flow of energy and materials between living organisms and the air, water, and soil. Biodiversity is necessary for the recycling of carbon, oxygen, nitrogen, phosphorous and other elements essential to plant and animal life.

Natural ecosystems provide numerous ecological services. They protect watersheds, provide water treatment, stabilize sensitive coastal zones, combat soil erosion and control soil quality, mitigate the effects of man-made pollution, and help regulate greenhouse gases. In addition, biodiversity acts as a buffer against extreme shifts in climate and weather and catastrophic ecological events. Biodiversity also provides man with the raw materials for food, shelter, energy, and medicine, as well as many aesthetic pleasures.
Ecosystem Serving The Planet
A 1993 report by the Biodiversity Unit of Australia's Commonwealth Department of the Environment, Sport and Territories identified a wide range of benefits to be gained by conserving biological diversity. Among these are several key ecological functions:

Soil formation and protection. Biodiversity is necessary to create and maintain soil structure, retain moisture and nutrient levels, and preserve the soil's productive capacity. Natural ecosystems also recycle life-essential nutrients from the soil and air. Biodiversity reduces the occurrence of landslides, protects against erosion of coastlines and riverbanks, and prevents damaging silt formations in coral reefs and riverine and coastal fisheries.

Protection of water resources. Naturally occurring vegetation provides critical ecosystem services, and its removal can seriously affect water resources. In water catchments, the natural vegetation cover regulates runoff and serves as a buffer against flood and drought, thereby maintaining consistent hydrological cycles. The effects of vegetation loss include reduced water quality and quantity, siltation of vital waterways, and degradation of aquatic habitats.

Climate stability. Plant life is also an important factor in regulating the Earth's climate. Undisturbed forest habitats recycle water vapor and return it to the atmosphere, while the forest canopies promote the atmospheric turbulence necessary to produce rainfall.

Pollution breakdown and absorption. Ecological processes lessen the harmful effects of pollution by breaking down and absorbing many manmade pollutants, such as oil spills, sewage, and other waste products. Many ecosystem components contribute to this natural environmental clean-up.

Recovery from unpredictable events. Diverse ecosystems rebound more quickly and fully from unpredictable natural disasters, as well as from those caused by man. In isolated or poorly conserved populations, plant and animal life are less likely to recover from fire, flood, cyclones or other catastrophic events.
And Man Looses More >>

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