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What Causes Species to Become Endangered?

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What Causes Species to Become Endangered?

Orangutan habitat destruction due to logging, mining and forest fires, as well as fragmentation by roads, has been increasing rapidly in the last decade.

Photo by Nonie / Wikimedia

We know that more and more species are on the verge of extinction, but why? Explore the major reasons why species become endangered and are added to the endangered species list.

Habitat Destruction

Every living organism needs a place to live. But habitat is not simply a home; it also is the place where an animal finds food and raises its babies. Then, of course, those babies need room to grow up, spread out, and live their own lives.

The trouble is, humans take up a lot of space on the planet. Not only do we build houses in wild animal habitats, we clear forests to get lumber and to make fields where we farm food. We plow up native plants to grow miles and miles of single crops like corn and wheat. We drain rivers to bring water to our crops, and many of our farming methods strip the soil of its nutrients and microbes. We pave meadows to make streets and parking lots.

As we're busting around making these "developments," we destroy animals' habitats and pollute the natural landscape with petroleum products, pesticides, and other chemicals. These actions kill some species outright and push others into areas where they can't find the food and shelter they need to survive. Often, when one animal suffers from human encroachment, it affects many other species in its food web, so more than one species' population begins to decline.

Habitat destruction is the most critical factor affecting the endangerment of species.

Introduction of Exotic Species

An exotic species is an animal, plant, or insect that is transplanted, or introduced, to a place where it did not evolve naturally. For example, a species like the bighead carp that is brought from China and turned loose in the United States.

Exotic species often have a predatory or competitive advantage over native species, which have been a part of a particular biological environment for centuries. Even though native species are well adapted to their surroundings, they may not be able to deal with species that closely compete with them for food or hunt in ways that native species has not developed defenses against. As a result, native species either cannot find enough food to survive or are killed in such numbers as to endanger survival as a species.

According to Endangered Species.com, a good example of endangerment due to both competition and predation is the Galapagos tortoise. "During the 20th century, goats introduced to the Galapagos Islands fed on the tortoises' food supply, and pigs, dogs and rats ate tortoise eggs. As a result, tortoise numbers went dramatically down."

Illegal Hunting

Species all over the world are hunted illegally (also known as poaching). When hunters ignore governmental rules that regulate the number of animals that should be hunted, they reduce populations to the point that species become endangered. Poachers are often hard to catch because governments don't have enough money to hire game wardens to patrol large tracts of wilderness. Poachers are also very sneaky. They transport live animals and animal parts in ways that are hard for law officials to track. Bird smugglers will bind live birds tightly to their legs so that they can't be seen when the criminals pass through airports. Baby bears, leopards, and monkeys have been sedated and stuffed into suitcases for transport. Live animals are sold to people who want exotic pets or medical research subjects. Animal pelts and other body parts are also secretly smuggled across borders and sold through "black market" networks of buyers who pay high prices for illegal animal products to be displayed as decorations or used in cosmetic products.

Legal Exploitation

Even legal hunting, fishing, and gathering of wild species can lead to population reductions that force species to become endangered. "Unrestricted whaling during the 20th century is an example of overexploitation," reports EndangeredSpecies.com. "The whaling industry brought many species of whales to extremely low population sizes. When several whale species were nearly extinct, a number of nations (including the United States) agreed to abide by an international moratorium on whaling. Due to this moratorium, some whale species, such as the grey whale, have made remarkable comebacks, while others remain threatened or endangered."

Natural Causes

Over the past 200 years, humans have made significant changes to natural environments all over the globe, and most of these changes have negatively affected wildlife, forcing unprecedented numbers of species toward extinction. However, extinction is a natural biological process that has been a part of species' evolution since the beginning of time. Fossil records have shown that, even before humans were a part of the world's biota, natural factors such as overspecialization , competition, sudden climatic change, or catastrophic events like volcanic eruptions and earthquakes have driven species to endangerment and extinction.

The University of Florida Extension Service lists the following characteristics that may predispose certain animals to becoming threatened or endangered:

  • Species with narrow habitat requirements
  • Species of economic importance (e.g., blue whale, sea turtle, ocelot, Atlantic salmon )
  • Species of large size, especially predators, and/or those intolerant of humans or vice versa (e.g., grizzly bear, Florida panther, bald eagle, Asiatic lion, gray wolf)
  • Species having limited numbers of offspring per breeding, long gestation periods, or those requiring extensive parental care (e.g., mountain gorilla, Mississippi sandhill crane, Abbott's booby, California condor)
  • Species with highly specialized adaptations, or high genetic vulnerability (e.g., manatee, Auckland flightless teal, red wolf, giant panda)
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