Reasons for Extinction

There is no single reason for extinction. The following are reasons for extinction:

• Rareness: Many species only exist in small numbers.

• Loss of habitat: When species lose their home, they are often unable to adjust to neighboring habitats or biomes.

• Disaster: Volcanoes, tornados, hurricanes, etc. can force a species to extinction.

• Climate change: Many species are unable to adapt to climate changes in their ecosystem.

• Disease: Naturally-occurring diseases can cause problems.

• Human-caused reasons: These reasons include hunting, pollution and loss of habitat.

• Imbalance in the ecosystem: The number of predators or prey may change the species ability to survive.

• Invasive species: Invasive species can often spread rapidly and out-compete other organisms for resources.

As you may have noticed, a lot of these reasons are interrelated. That's because changes to an ecosystem often have a large number of effects. For example, humans chopping down a forest for wood mean a loss of prey and habitat.

The number one problem facing wildlife today is the loss of habitat by human activity. At no other time in Earth's history has there been such a high rate of species loss than there is today. According to Harvard University Biologist E.O. Wilson, changes to wildlife habitat due to human activity dooms to extinction three species each hour, 74 each day, and 27,000 each year. This rate of extinction is 1,000 to 10,000 times faster than any other time in the geologic history of our planet. If current destruction of rainforests and other habitats continues, it is estimated that one-fifth of the 1.2 million species on Earth will become extinct by 2022.



Sources
http://library.thinkquest.org/J002558F/extinction.htm (fair use)
http://www.nps.gov/piro/forteachers/wildlifemgtguide.htm (gov site. public domain)