Endangered Species, plant and animal species that are in danger of extinction, the dying off of all individuals of a species. Over 8,300 plant species and 7,200 animal species around the globe are threatened with extinction, and many thousands more become extinct each year before biologists can identify them. The primary causes of species extinction or endangerment are habitat destruction, commercial exploitation (such as plant collecting, hunting, and trade in animal parts), damage caused by nonnative plants and animals introduced into an area, and pollution. 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. Species have slowly evolved and disappeared throughout geologic time because of climatic changes and the inability to adapt to survive competition and predation. 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 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 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 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..............
