Animal Endangerment and its Causes - Dearborn Public Schools



Animal Endangerment and its CausesThe Siberian tiger is an endangered tiger subspecies. Three tiger subspecies are already?extinct.Living things have been disappearing since the beginning of life on our planet. In fact, most species that have ever lived on Earth are now extinct.?Extinction and endangerment can occur naturally as a normal process in the course of evolution. Or, it can be the result of a major event, such as an asteroid colliding with Earth.?For example, scientists believe an asteroid struck near Mexico's Yucat?n Peninsula?about 65 million years ago. Almost 50 percent of plant species and 75 percent of animal species, including the dinosaurs, became extinct.?Scientists have identified five great extinction episodes like this before humans even appeared on the planet.?Species throughout history have disappeared due to?disease, competition or natural climate change.However, when humans became the dominant species, the extinction rate of other species began to increase dramatically.?Especially since the 17th century, technological advances and the increasing number of people have changed the world.Jaguar at the Edinburgh Zoo in Scotland. Jaguars need a great deal of space to thrive, but their territory has been encroached upon by human activity. Photo: Pascal Blachier/Wikimedia. [click to enlarge]Species are disappearing faster than they can be created.?Therefore, the planet has entered a sixth wave of mass extinction that scientists believe is caused by human activity.It is impossible to measure the number of species going extinct because there are millions that have not yet been discovered. However, it is thought that amphibians and corals are the animal groups at highest risk of extinction because about 40 percent of each group is currently threatened. Meanwhile, about 25 percent of mammals and 13 percent of birds are at risk.People contribute to the loss of species primarily in three ways, which are habitat destruction, commercial use of animals and plants, and the introduction of non-native species, also known as an invasive species, into a habitat. If climate change continues at its current pace, 25 percent of all species could be at risk by 2050.Habitat DestructionThe destruction of habitats all over the world is the primary reason species are becoming extinct or endangered. Houses, highways, dams, industrial buildings, and farms sit on what used to be forests, deserts and wetlands.For instance, 46,000 to 58,000 square miles of forest each year are destroyed worldwide, the equivalent of 36 football fields each minute. Tropical rain forests, home to 50 percent of all animal and plant species, once occupied 6 million square miles worldwide. Now, only 2.4 million square miles remain.Habitat destruction does not just come from building structures. Pollution, such as sewage from cities and chemical runoff from farms, can flow into streams and rivers, which can endanger species.When species' habitats become smaller and smaller, they become crowded. There is also more competition for fewer resources and space, so access to food, water and mates may become limited.?Commercial ExploitationThroughout history, animals have been hunted by humans for their meat and in order to make clothing, medicines, art and other things. Overhunting has caused the extinction of many species and brought a great many others to the brink, including whales, the black rhinoceros and the bluefin tuna. Other species are threatened because they are collected or captured as pets or for trading. Elephants, for instance, face the constant threat of poaching because of the value of their ivory tusks.?International treaties, such as CITES, which stands for the Convention on International Trade of Endangered Species, outlaw the capture and trade of many species. Unfortunately, these laws are very difficult to enforce. Many endangered species live in remote areas that are hard for law enforcement officers to fully monitor.?Non-Native SpeciesNative species are those that have lived in a certain place for a long period of time and they have adapted to the environment, climate and other species also living there.?Introduced species are those that have been brought into that landscape by humans, either accidentally or intentionally.?In some cases, these introduced species may not cause any harm and may adapt in time. However, introduced species?most often?throw off ecological balances because they compete with native species for food and shelter. They may also prey on the native species and carry diseases that infect them.When introduced species cause harm to an environment, they are called invasive species. More than 40 percent of threatened or endangered species are at risk because of invasive species.Climate ChangeHumans burn fossil fuels such as coal to make electricity. We burn gasoline to power our?cars. Burning fossil fuels releases?carbon dioxide into the air; which?traps Earth's heat.?The more carbon dioxide in the atmosphere, the warmer Earth becomes. Levels of carbon dioxide in the atmosphere have increased since the period known as the industrial revolution began in the 19th century.?Earth's temperature is still continuing to increase, which is referred to as global warming. A related term, climate change, refers to all major, long-lasting changes in climate. This includes global warming but also longer, more severe heat waves and changes in rainfall that lead to floods or droughts. These heat waves and rainfall changes are linked to increased levels of carbon dioxide and other gases in the atmosphere.Climate change threatens many species in many ways.?Melting sea ice causes sea levels to rise, which could engulf areas where animal and plant species live.?Warmer temperatures on land can force animals to move to cooler areas or wake animals too early from hibernation. Droughts threaten many animals, especially amphibians, and plants. Often the effects of climate change cause a chain reaction. One example is rising temperatures reducing the algae population. This harms sea animals that eat algae and then harms larger animals, like whales that eat those sea animals.Some scientists believe climate change has already contributed to the extinction of one species: the golden toad, a small, bright orange amphibian from Central America. ................
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