Endangered Species of South Am

Endangered Species of South America
Endangered species are plant and animal species that are in danger of extinction, the dying off of all individuals of a species. 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 (Microsoft 1). The primary cause of species extinction or endangerment are habitat destruction, commercial exploitation, damage caused by non-native plants and animals introduced into an area, and pollution (1). Of these causes, direct habitat destruction threatens the most species.

A steady rate of extinction is a normal process in the course of evolution, and is called the background rate of extinction (Lampton 14). Species have slowly evolved and disappeared throughout geological time because of climate changes and the inability to adapt to survive competition and predation. Since the 1600's, however, the rate of extinction has accelerated rapidly because of human population growth and resource consumption (17). 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 (17). 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 (18).

The survival of ecosystems (plant and animal communities and their physical surroundings) such as forests, coral reefs, or wetlands depend on their biodiversity 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 ecosystems 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 and other wildlife, such as sea otters. When the sea otter population off the western coast of Canada and the U.S. was hunted almost to extinction in the 19th and early 20th centuries, invertebrates such as the sea urchins 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 (Grolier 41). Conservation efforts throughout the latter half of the 20th century, such as the U.S. Marine Mammal Protection Act (1972), allowed for the protection and reintroduction of the sea otter to these ecosystems and kelp forests once thrived again (41).

The irreversible loss of biodiversity 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 biodiversity provides. As many as 40 percent of our modern pharmaceutical medicines are derived from plants and animals (Fast Facts about Endangered Species 1). A small plant from Madagascar, the rosy periwinkle, produces substances that are effective in fighting two deadly cancers, Hodgkin's disease and Leukemia (Newman 135). Yet the forest habitat of the rosy periwinkle is rapidly disappearing to supply firewood and farmland for the impoverished people of Madagascar, and most of the endemic species there - that is, species that live nowhere else - are endangered.

Species become endangered or extinct for a number of reasons, but the primary cause is the destruction of habitat by human activities. 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 available habitats (Microsoft 2). Habitat fragmentation has caused plant and animal species in the remaining islands of habitat to lose contact with other population of their own kind. This reduces their genetic diversity and makes them less adaptable to environmental or climate change (Lampton 21).

Since the 1600's, worldwide commercial exploitation of animals for food and other products has caused many species to become extinct or endangered (Microsoft 2). The whaling industry, in which whales are slaughtered for oil and meat, has led many whale species to the brink of extinction (2). Virtually entire families of plants such as cactus, orchids and cyads are considered threatened or endangered because of over-collection for commercial purposes (2).

Non-native 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 (Newman 92). 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 irreversibly, and there is often no way to keep the damage from spreading.
Pollution is another important cause of extinction. Toxic chemicals - especially chlorinated hydrocarbons, such as dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCB's) - have become concentrated in food webs, the interconnected food chains that circulate energy through an ecosystem (Microsoft 3). These toxic chemicals strongly affect species near the top of the food chain. Both DDT ; PCB's interfere with the calcium metabolism of birds, causing soft-shelled eggs and malformed young. PCB's also impair reproduction in some carnivorous animals (Newman 33). Water pollution and increased water temperature 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 results of extreme air pollution, has been known to kill organisms in freshwater lakes and destroy large tracts of forested land (Microsoft 3).

In any effort to produce global biodiversity and encourage the study, restoration, and sound management of endangered species the IUCN and the World Conservation Monitoring Centre (WCMC) maintain a global list of endangered species and vulnerable animals called the Red List. A framework for international conservation efforts, the Red List database accesses the status of, and threats to, animals species worldwide (IUCN Red List of Threatened Animals Database Search Results 1).

Efforts to save endangered species also include captive breeding of severely endangered species later released in the wild to restore or add to a breeding population (Microsoft 4).

Captive breeding is considered a last resort because such breeding may reduce the genetic diversity of the species and it's ability to survive the wild. Captive-bred animals, extremely difficult to successfully reintroduce to the wild, are more likely to carry disease, which they may transmit to the wild population (Lampton 36). Captive breeding programs are extremely costly, sometimes reaching over $500,000 per year per species (Microsoft 4).
The scientific field of conservation biology evolved to study the complex problems surrounding habitat destruction and species protection. The objectives of conservation biologists are to understand how humans affect biodiversity and to provide potential solutions that benefit both humans and non-human species.

One of the approaches that conservation biologists study and implement is the development of habitat reserves. All species require a minimum amount of habitat for survival. Wildlife habitat reserves are established to meet these requirements for as many species as possible. Some national parks, wilderness areas, and other protected habitats are suitable for the survival of a wide range of species. Unfortunately, the minimum required by large carnivores such as grizzly bears or cougars may be larger than the area protected in a reserve. In order to effectively enlarge the area available to the species, protected areas that connect separate reserves may be developed. These areas are narrower than the actual reserve, but allow for easy travel between reserves. Conservation biologists recommend that reserves be surrounded by a wide belt of landscape to maintain the effectiveness of the reserve. Conservation biologists also study and promote habitat restoration and extensive public education, and work with ecologists and taxonomists to identify and describe the millions of imperiled species not yet known to science.

The current global extinction crisis is one of the greatest challenges posed by the rapid growth and expansion of human populations. The protection of endangered species and habitats should be a top priority for the international organizations, government agencies, industry, and individuals if there is hope for preserving the earth's valuable biodiversity for future generations.

Works Cited
"Endangered Species." Microsoft Encarta, 1993-1997.

"Endangered Species; South America, 1." Grolier World Encyclopedia, 1993.

"Fast Facts about Endangered Species." EAC. http://www.worldkids.net/eac/fastfact.htm
(8 April 1999).

"IUCN Red List of Threatened Animals Database Search Results." World
Conservation Monitoring Centre. http://wcmc.org.uk/cgi-bin/arl_output.p
(1 April 1999).

Lampton, Christopher. Endangered Species. New York: Impacts, 1980.

Newman, Arnold. Tropical Rainforests. New York: Facts on File, 1990.