Monoculture, the agricultural method of growing a single crop, can also reduce genetic variation. Modern agribusiness relies on monocultures. Almost all potatoes cultivated, sold, and consumed, for instance, are from a single species, the Russet Burbank. Potatoes, native to the Andes Mountains of South America, have dozens of natural varieties. The genetic variation of wild potatoes allows them to adapt to climate change and disease. For Russet Burbanks, however, farmers must use fertilizers and pesticides to ensure healthy crops because the plant has almost no genetic variation. Ebony ( Diospyros crassiflora) is a tree native to the rain forests of central Africa, including Congo, Cameroon, and Gabon. Ebony is an endangered species because many biologists calculate its probability of extinction in the wild is at least 20 percent within five generations. Species that are not threatened by extinction are placed within the first two categories—least concern and near-threatened. Those that are most threatened are placed within the next three categories, known as the threatened categories—vulnerable, endangered, and critically endangered. Those species that are extinct in some form are placed within the last two categories—extinct in the wild and extinct.

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The Siberian sturgeon is an endangered species because its total population has declined between 50 and 80 percent during the past 60 years (three generations of sturgeon). Overfishing, poaching, and dam construction have caused this decline. Pollution from mining activities has also contributed to abnormalities in the sturgeon’s reproductive system. A critically endangered species’ population has declined between 80 and 90 percent. This decline is measured over 10 years or three generations of the species, whichever is longer. Threatened categories have different thresholds for these criteria. As the population and range of the species decreases, the species becomes more threatened. The San Diego Zoo, in southern California, is the largest zoo in the United States. It is a suburbanzoo that houses more than 4,000 animals (800 different species) in its 0.4 square kilometers (100 acres). Landscape immersion divides animals into their natural habitats, such as the tundra (with reindeer and polar bears) or bamboo forest (featuring pandas.) The San Diego Zoo also includes a wild animal park, which is even more expansive (almost 8 square kilometers or 2,000 acres.) Biologists, anthropologists, meteorologists, and other scientists have developed complex ways to determine a species’ probability of extinction. These formulas calculate the chances a species can survive, without human protection, in the wild.

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The Bolivian chinchilla rat ( Abrocoma boliviensis) is a rodent found in a small section of the Santa Cruz region of Bolivia. It is critically endangered because its extent of occurrence is less than 100 square kilometers (39 square miles). The major threat to this species is loss of its cloud forest habitat. People are clearing forests to create cattle pastures. A species is extinct when there is no reasonable doubt that the last remaining individual of that species has died. The definitions of the three threatened categories (vulnerable, endangered, and critically endangered) are based on five criteria: population reduction rate, geographic range, population size, population restrictions, and probability of extinction. A species is classified as critically endangered when its population has declined at least 90 percent and the cause of the decline is known. A species is also classified as endangered when its population has declined at least 80 percent and the cause of the decline is not known.

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When a species is classified as endangered, governments and international organizations can work to protect it. Laws may limit hunting and destruction of the species’ habitat. Individuals and organizations that break these laws may face huge fines. Because of such actions, many species have recovered from their endangered status. Petting zoos feature domesticated animals that are gentle enough for children to pet and feed. Sheep, goats, donkeys, and rabbits are common petting zoo animals. A species is classified as endangered when its population is restricted to less than 250 mature individuals. When a species’ population is this low, its area of occupancy is not considered.Access-restricted-item true Addeddate 2021-04-17 14:00:37 Associated-names National Geographic Society (U.S.) Boxid IA40089307 Camera Sony Alpha-A6300 (Control) Collection_set printdisabled External-identifier

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Development can also endanger species indirectly. Some species, such as fig trees of the rain forest, may provide habitat for other species. As trees are destroyed, species that depend on that tree habitat may also become endangered. Tree crowns provide habitat in the canopy, or top layer, of a rainforest. Plants such as vines, fungi such as mushrooms, and insects such as butterflies live in the rain forest canopy. So do hundreds of species of tropical birds and mammals such as monkeys. As trees are cut down, this habitat is lost. Species have less room to live and reproduce. Early zoos like the Menagerie du Jardin des Plantes were more like museums of living animals than natural habitats. Animals were kept in small display areas, with as many species as space would allow. The brown pelican was taken off the endangered species list in 2009, for instance. This seabird is native to the coasts of North America and South America, as well as the islands of the Caribbean Sea. It is the state bird of the U.S. state of Louisiana. In 1970, the number of brown pelicans in the wild was estimated at 10,000. The bird was classified as vulnerable. Species with fewer than 10,000 mature individuals are vulnerable. The species is also vulnerable if that population declines by at least 10 percent within 10 years or three generations, whichever is longer. The first modern zoo, built in 1793, opened in Paris, France. The menageries of French aristrocrats, including the king and queen, were taken by leaders of the French Revolution and relocated to the Ménagerie du Jardin des Plantes. The facility is still a busy and popular zoo in downtown Paris.In many urbanzoos, animals are kept in relatively small enclosures. Some animal activists argue that keeping animals in urban settings is cruel because of cramped conditions, noise, and pollution. A species is extinct in the wild when it only survives in cultivation (plants), in captivity (animals), or as a population well outside its established range. A species may be listed as extinct in the wild only after years of surveys have failed to record an individual in its native or expected habitat.

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A species is classified as critically endangered when its population is restricted to less than 50 mature individuals. When a species’ population is this low, its area of occupancy is not considered. Urbanzoos, located in large cities, still resemble the smaller zoos that were popular 200 years ago. Often, these zoos sit in the middle of cities, making expansion difficult. There is little room for urbanzoos to grow, and many of the zoo’s buildings are historic landmarks that cannot be destroyed or redesigned. The Transcaucasian racerunner ( Eremias pleskei) is a lizard found on the Armenian Plateau, located in Armenia, Azerbaijan, Iran, and Turkey. The Transcaucasian racerunner is a critically endangered species because of a huge population decline, estimated at more than 80 percent during the past 10 years.

The goal of many captive breeding programs at zoos is the re-introduction of animals into the wild. The California condor, a very large bird native to the west coast of the United States, has been re-introduced to its native habitat after breeding in zoos and wildlife parks. There are several breeding pairs of California condors in the wild today. During this time, people started wanting to study animals for scientific reasons. Scientists wanted to research animal behavior and anatomy. To do this, scientists and zookeepers had to keep animals in places that were close to, or resembled, the animals’ natural habitats.