The Living World - Extinction of Species

Description:

Many species are experiencing extinction from earth because of various factors. Some of the factors include −

Natural extinction (Background extinction)

• Some organisms are disappearing due to change in the environment.
• This is a gradual continuing process and has occurred in geological past.

Mass extinction

• At times several species disappear due to catastrophes.
• One example is the disappearance of dinosaurs along with loss of more than 50% of the existing species.
• Global warming may cause mass extinction in future.

Anthropogenic extinction

• Due to human interference, loss of biodiversity is taking place.
• This leads to disappearance of number of species and it takes place within short span of time.
• Habitats have been disturbed due to which these are near extinction.

The International Union for Conservation of Nature and Natural resources (IUCN) maintains a Red Data Book which contains records of animals which are known to be in danger.

IUCN has developed 8 Red list categories based on the degree of threat. These categories are −

• Extinct −  When there is no reasonable doubt that the last individual has died.
• Extinct in the wild − When extensive surveys, in known or expected habitats have not recorded an individual.
• Critically endangered − Facing high risk of extinction in the wild or near future.
• Endangered − Not critically endangered, but facing high risk of extinction in near future.
• Vulnerable − Not critically endangered or endangered but facing high risk of disappearance in mid-term future.
• Lower risk − When it has been evaluated but it does not satisfy the criteria for critically endangered, endangered or vulnerable.
• Data deficient − When there not sufficient information to make direct or indirect assessment of its risk of extinction.
• Not evaluated − When it has not been assessed in any of the above criteria.