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Endangered Species

By Mehrose Hossain
Over 19.000 plant species and 5000 animal species around the globe are classified as endangered, and many thousands more become extinct each year before biologists can identify them. A steady rate of extinction is a normal process in the course of evolution, and is called the background rate of extinction. Species have slowly evolved and disappeared throughout geologic time because of climatic changes and the inability to adapt to survive competition and perdition. Since the 1600s. however, the rate of extinction has accelerated rapidly because of human population growth and resource consumption.
Today most of the world's habitats are changing faster than most species can adapt to such changes through evolution or natural selection. The current global extinction rate Is estimated at about 20.000 species per year, exponentially greater than the background extinction rate. Many biologists believe that we are in the middle of the greatest mass extinction episode since the disappearance of the dinosaurs 65 million years ago. The survival of ecosystems (plant and animal communities and their physical surroundings) such as forests, coral reefs, or wetlands depends on their bio-diversity, or variety of plants, animals, and habitats, as well as the many interactions among these species.
The removal or disappearance of one or several species may irreversibly damage the ecosystem and lead to its decline. For example, the undersea kelp forest ecosystems of the northern Pacific Rim are some of the richest marine habitats known they are the home or breeding ground of many species of fish and other wildlife, such as sea otters. When the sea otter population off the western coast of Canada and the United States are hunted almost to extinction In the 19th and early 20th centuries, invertebrates such as the sea urchin were left without a major predator. The population of sea urchins increased dramatically and rapidly consumed the kelp and other seaweed, turning the rich ecosystem Into a barren undersea terrain.
Conservation efforts throughout the latter half of the 20th century, such as the US Marine Mammal Protection Act (1972), allowed for the protection and reintroduction of the sea otter to these ecosystems and the kelp forests once again thrived. The irreversible loss of bio-diversity has a serious Impact on the ability of remaining species, including humans, to survive. Humans depend on species diversity and healthy ecosystems to provide food, clean air and water, and fertile soil for agriculture. In addition, we benefit greatly from the many medicines and other products that blo-dlversity provides. As many as 40 per cent of our modern pharmaceutical medicines are derived from plants or animals.
Species become extinct or endangered for a number of reasons, but the primary cause in the destruction of habitat by human activities (see Environment). As species evolve, most adapt to a specific habitat or environment that best meets their survival needs. Without this habitat the species may
not survive. Pollution, drainage of wetlands, conversion of shrub lands to grazing lands, cutting and clearing of forests, urbanization, coral-reef destruction, and road and dam construction have destroyed or seriously damaged and fragmented available habitats. Habitat fragmentation, the isolation and division of habitats into smaller areas has caused plant and animal species in the remaining islands of habitat to lose contact with other populations of their own kind. This reduces their genetic diversity and makes them less adaptable to environmental or climatic change. These small populations are highly vulnerable to extinction. For some species, the fragmented habitats become too small to support a sustainable population.
Since the 1600s, worldwide commercial exploitation of animals for food and other products has caused many species to become extinct or endangered. The whaling industry, in which whales are slaughtered for oil and meat, for example, has led many whale species to the brink of extinction The African black rhinoceros, killed for its hom, which is prized as a medicine and aphrodisiac, is also critically endangered The great auk and the passenger pigeon became extinct in the 19th and early 20th centuries because of over hunting and the Carolina parakeet perished as a species because of a combination of over hunting and habitat destruction. Virtually entire families of plants such as cactus, orchids and cycads are considered threatened or ■ endangered because of over-collection for < ommerdal purposes. Non-natlve species introduced to a new ecosystem have caused serious native species declines. The non-native, or exotic, species may be introduced either accidentally or intentionally, and either out-compete the native species or prey on them Native plants and animals may have no defenses against these invaders, which can exterminate or greatly reduce the populations of many native species
The damaging effects are generally irreversible, and there is often no way to keep the damage from spreading. The accidental introduction of blight, for example, virtually eliminated the American chestnut tree from North American hardwood forests. The zebra mussel first discovered in North America in Lake Victoria in eastern Africa s a sport fish This large predator drastically reduced native fish populations c md caused the extinction of as many as 200 endemic species of cichlld fish. Because the cichlids are important algae-feeding fish, the lake has since become choked with decomposing aquatic vegetation, depleting the oxygen in the water and leading to further species declines.
Pollution is another important cause of extinction. Toxic chemicals especially chlorinated hydrocarbons, such as dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCBs) have become concentrated in food webs, the interconnected food chains that circulate energy through an ecosystem. These toxic chemicals strongly affect species near the top of the food chain Both DDT and PCB’s interfere with the calcium metabolism of birds, causing soft-shelled eggs and malformed young. PCBs also impair ■reproduction in some carnivorous animals. Water pollution and increased water temperatures have wiped out endemic species of fish in many habitats. Oil spills destroy birds, fish, and mammals, and may contaminate the ocean floor for many years after the event. Acid rain, the toxic result of extreme air pollution, has been known to kill organisms In freshwater lakes and destroy large tracts of forested land.
In an effort to protect global bio-diversity and encourage the study, restoration, and sound management of endangered species the IUCN and the World Conservation Monitoring Center (ACMC) maintain a global list of endangered and vulnerable animal species called the Red Ust. A framework for international conservation efforts, the Red List database assesses the status of, and threats to, animal species worldwide To add to this and other bio-diversity databases, non governmental organizations such as Conservation International .ind World Wildlife Fund conduct periodic rapid assessments (focused. Intensive evaluations) of biodiversity in various hotspots regions like Madagascar that are both rich in endemic species
and is also environmentally threatened Tills information rs used in the administration of international agreements such as the Convention on International trade in Endangered Species of Wild Fauna and Flora (CITES), signed by 125 nations in 1973 and put into effect in 1975
The purpose of CITES Is to restrict exploitation of endangered plants and wildlife by regulating and restricting their trade. Despite legal protection, however, the future of many species, such as the African black rhinoceros, is in doubt because of poor law enforcemen' and the activities of poachers and dealers who supply the S6 billion per year trade in endangered animals and animal parts. Similarly, the International Whaling Commission is charged with protecting global whale populations, but lacks the authority to enforce its rulings. Several pnvate and governmental efforts in the United States have been mobilized to save endangered species One immediate approach is to protect a species by legislation.
The Lacey Act of 1900 was enacted to protect wildlife from commercial trade and over hunting Th< Marine Mammal Protection Act of 1972 banned the killing and importing of whales and nearly all marine mammals. In addition to promoting species and habitat protection in the United States, the Endangered Species Act (ESA) discouraged the exploitation of endangered species in other countries by banning the importation and trade of any product such as elephant-tusk ivory, obtained from such species. Although the ESA is one of the most progressive national wildlife protection laws evri enacted, it is constantly threatened by development industries unhappy with the government restrictions
The United ftales also has various agreements with other nations like Canada and Mexico for tin legal protection of migratory birds These include the Migratory Bird Treaty Act of 1918, the Migratory Bird Conservation Act of 1929, and the North American Waterfowl Management Plan of 1986 Canadian laws designed to protect endangered species include the Migratory Birds Convention Act of 1917, the Canadian Endangered Species Protection Act ol 1996, and the Wild Animal and Plant Protection and Regulation of International and Inter-provincial Trade Act of 1996
The current global extinction crisis is one of the greatest challenges posed by the rapid growth and expansion orhuman populations. The protection of endangered species and habitats should be a top priority for international organizations. _..,.rnmental agencies, industry, and individuals if there is hope for preserving the earth's valuable biodiversity for future generations
Dear Mehrose,
Yours is undoubtedly a good piece of research work, but it is only proper to give credit to the books you have done your research from, otherwise there is always Ilie risk ol others calling it a plagiarized work —RS Desk