Biodiversity—the vast numbers of species of plants and animals interacting on Earth—provides people with food, building materials, fibers, and medicines. Insects pollinate crops, wild plant genes reinvigorate domestic ones, forests provide breathable air, microorganisms create soil, and aquatic microorganisms cleanse and purify water. Without the millions of known and unknown species operating interdependently, life on Earth would be impossible for human beings. Yet life-forms are dying off at an unprecedented rate. Biologists estimate that there were 1 million fewer species in 2000 than in 1900.
The U.S. Endangered Species Act of 1973 defines an endangered species as one that is on the brink of extinction. A threatened species is defined as one with a good chance of becoming endangered in the foreseeable future. What pushes a healthy animal species into the threatened category? Almost all of the answers involve human beings. Either through misuse, thoughtlessness, or overconsumption of Earth's resources, humans are the source of the current mass extinction.
As human populations soar, more and more of the world's natural habitats are being destroyed. Forests are cleared for logging, shopping centers, and housing developments. Wetlands are drained for farms and factories. Valleys and rivers are flooded for hydroelectric power and recreation. Oil spills at sea threaten marine life. Acid rain from factories and automobile exhaust, pesticides scattered indiscriminately and chemical pollution of air and water further stress animal species. Legally protected animals are poached in wildlife preserves for their body parts, and ranchers and hunters exterminate grizzlies, wolves, large cats, and prairie dogs alike for trophies or because they consider them to be a nuisance.
One of the species headed for endangered status is the Pribilof seal. About 30,000 a year die entangled in plastic fishing lines and six-pack aluminum can holders. Most species require a critical number of members in order to successfully breed. The Key deer and Florida panther are diminishing below the breeding population (the number of individuals necessary for the species to breed successfully) because of deaths by automobile. Manatees are equally threatened due to collisions with motorboats.
Among the other threatened species are the whales, who are killed for their body parts. Mountain gorillas and pandas are threatened by shrinking habitat and food sources as human populations press in on their range. Asian tigers, South American jaguars, and snow leopards are disappearing as their pelts are sold as souvenirs. Sea turtles are hunted for their shells, reptiles for their skins, and rare birds are trapped to be sold as pets.
The numbers of unidentified species vanishing forever from the tropical rain forests, home to the greatest amount of life on Earth, has become a cause of great concern to environmentalists. The most disturbing phenomenon connected to the disappearing rain forests is that they are being destroyed to make room for ranches built to breed cattle that will eventually provide inexpensive meat products for developed nations.
Like the dinosaurs 65 million years ago, humanity finds itself at the top of a food chain that is in the midst of a mass extinction. A mass extinction is a traumatic event. As the food chain falls apart, the survivors scramble to reassemble a workable ecosystem . For example, should the food of any common prey, such as rabbits or mice, become scarce, the numbers of those species will drop. This will set off a chain reaction that affects all the ground and air predators that feed on them, such as, coyotes, badgers, hawks and owls. The largest, most resourceful consumptive species do not survive. Ultimately, if humans continue to abuse the intricate ecological mechanisms that keep the world running smoothly, humans themselves may prove to be the most threatened species of all.
see also Endangered Species; Extinction; Habitat Loss; Habitat Restoration.
Bailey, Jill, and Tony Seddon. The Living World. Garden City, NY: Doubleday, 1986.
Lampton, Christopher. Endangered Species. New York: Franklin Watts, 1988.