Most extinctions that have occurred throughout Earth's long history have been a result of natural factors. However, recent evidence suggests that human-made factors may be the cause of many extinctions arising today.
Endangered Species
Over 7,000 species around the world are considered endangered. That number doesn’t even include the plants, animals, and other life-forms that are listed by some scientists as vulnerable, critically endangered, or extinct in the wild—all these classifications just mean a species is getting closer and closer to extinction.
So how does a species become endangered, and who decides?
- While different governments have their own way of deciding, the International Union for Conservation of Nature (IUCN) maintains the most-comprehensive list of endangered species around the world.
- The Red List of Threatened Species, judges each species on five different standards.
According to the IUCN, an endangered species is one that meets any one of the following criteria:
- A 50–70% population decrease over 10 years.
- A total geographic area less than 5,000 km2 (or local population area less than 500 km2).
- A population size less than 2,500 adults.
- A restricted population of 250 adults.
- A statistical prediction that it will go extinct within the next 20 years.
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Topic Tips
- An endangered species is a species that is very likely to become extinct in the near future.
- Many species today appear to be significantly threatened or endangered due to human-made factors.