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Biodiversity |
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Definition of Biodiversity
Biodiversity refers to the diversity of living organisms and the ecosystems and processes of which they are part. It includes animals, plants, fungi, algae, protozoa, bacteria and viruses. It is most often used in the context of flora and fauna and those organisms required to sustain the ecosystems necessary for these higher life forms.
Biodiversity is usually considered at three different levels: genetic diversity, species diversity and ecosystem diversity.
Genetic diversity is the sum total of genetic information contained in the genes of the individual animals, plants, and microorganisms that inhabit the earth.
Species diversity refers to the variety of living organisms on earth. Globally, a total of about 1.5 million species has been described. Estimates of the total number of species vary between 5 and 50 million with a figure of 10 million being generally accepted.
Ecosystem diversity relates to the variety of habitats, biotic communities and ecological processes that occur on earth. Ecosystem diversity is easier to measure and is often used as the basis of land management and conservation.
Variability of Biodiversity
The level of biodiversity on a worldwide basis is highly variable. The greatest diversity occurs in tropical forests. Although these areas cover only about 7% of the earth's land surface, they account for more than half the world's species (some estimates place the number as high as 70% to 90%). Other habitats that are particularly rich in diversity include areas with Mediterranean-like climates, islands, coral reefs, and some lakes.
While areas especially rich in species or endemic species (those with limited ranges) occur most often in the tropics, scientists caution that preservation of other less diverse areas, such as arid zones, is also critical to maintaining the world's biodiversity.
Biodiversity as a Worldwide Issue
Although humans have inhabited this planet for many thousands of years, our population has been low (less than half a billion) and sparse until relatively recent times. In 1950 the world's human population was 2.6 billion. It grew to 5 billion by 1989. In 2025 the population is projected to reach 8.5 billion. This population
growth causes increasing pressure for more space, food, energy and natural resources. The ecosystem destruction resulting from meeting the needs of the growing population has led to a loss of biodiversity.
Loss of habitat is considered the greatest current threat to biodiversity. However, other important factors include competition from or predation by introduced plants and animals, and susceptibility to introduced pathogens. Introduced species of birds, insects, animals, plants, and bacteria have had significant ecological impacts in many parts of the world.
Although the actual numbers can never be known, extinction of plant and animal species is occurring at a high rate. Extinction rate estimates ranging from thousands to tens of thousands of species per year have been published in the scientific literature. Some extinction is a normal part of the evolutionary process, but it is generally accepted by the scientific community that the high rate that is currently being experienced cannot be sustained without serious implications.
Ecosystem losses are also occurring. Globally, half of all marshes and wetlands have been filled or drained. In North America, 99% of tall grass prairies have been lost. Estimates are that Latin America loses 1.3% of its remaining forest each year. Such ecosystem losses are clearly not a natural part of the evolutionary process.
As an expression of the growing worldwide concern, representatives of more than 150 countries signed an international Convention for the Conservation of Biological Diversity at the U.N. Conference on Environment and Development held in Rio de Janeiro in June 1992. The Convention came into force in December 1993.
Values of Biodiversity
Maintenance of the diversity of biological resources helps ensure the continued viability and balance of life by sustaining ecosystems, many of which are highly interdependent. While the values of biological resources may not always be quantifiable, or represent a direct benefit to humans, they are nonetheless significant. They include the range of resources which are the basis of survival by providing a food source, shelter or warmth.
Some values can be measured in monetary terms, for example, products that are harvested by humans and exchanged in formal markets. National income accounts typically identify values for harvesting of fuelwood, timber, game, fish, skins, medicinal plants, honey, fibers and so forth. Overexploitation for human use, e.g., fish stocks, can be a significant threat to biodiversity in itself.
It is not possible to place a monetary value on resources and processes that are of major benefit but are not directly consumed by humanity. Maintenance of water cycles, prevention of erosion, production of soil, provision of recreational, scientific and aesthetic values are illustrations of these very important resources and processes. A broad gene pool is essential for the development and maintenance of a stable ecosystem.
There are other less tangible values of biodiversity such as potential future values of medicinal, genetic, chemical and economic resources. A good example is that of communal animals. Ants, termites, wasps etc. have developed contagious disease resistance systems through millions of years of communal evolution. The solutions to some human disease problems may be found through the careful scientific study of these kinds of organisms.
Although factors such as cultural background and economic well-being influence people's perceptions differently, the conservation of plant and animal species is widely seen in many countries as an important ethical issue.
Alcoa's Position on Conservation of Biodiversity
Consistent with Alcoa's environmental policy and its published position on sustainable development, the company actively endorses the concept of conservation of biodiversity by operating worldwide in a manner which minimizes impacts on natural habitats and biological resources.
Alcoa's operations can play a positive role in conserving biodiversity by adopting appropriate land management practices (reference position paper on Land Management) and rehabilitating land disturbed by the operations in an appropriate manner (reference Bauxite Mine Rehabilitation Standards and Guidelines).
New or expanding operations should document the level of ecosystem and species diversity within their area of influence by applying techniques, procedures, and information generally accepted by the international scientific community. Measures to minimize adverse impacts on ecologically significant ecosystems or species should be adopted. Particular attention should be paid to the conservation of rare biological communities and rare, endangered or threatened species.
Where relatively extensive operations such as bauxite mining are carried out in natural habitats, rehabilitation of the disturbed land should in most circumstances favor the return of the pre-existing vegetation and fauna communities. Such rehabilitation should aim to re-establish the broadest practicable genetic base using local genetic material and provenances wherever possible.
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