Endangered Species of South Am Essayerica
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 .
