Endangered organisms, extinction and the Red Data Book
The Red Data Book, kept by the IUCN as its Red List, records extinct and threatened species. It shows that extinctions today are far faster than natural rates.
Types of extinction
| Type | Cause | Example |
|---|---|---|
| Natural (background) extinction | Slow change in the environment over long periods; some species fail to adapt | The steady loss of species seen through the fossil record |
| Mass extinction | Catastrophic events wipe out huge numbers of species in a short geological time | Five in Earth's history; the dinosaurs died out in the last one, about 65 million years ago |
| Anthropogenic (human-caused) extinction | Habitat loss, over-hunting, invasive species and pollution | Dodo, passenger pigeon, Steller's sea cow; today's sixth extinction |
The Red Data Book
The Red Data Book is a record of species that are extinct or at risk of extinction, with their status and the threats they face. The IUCN (International Union for Conservation of Nature and Natural Resources) keeps it as the IUCN Red List, and your textbook quotes its 2004 edition. Your textbook calls an organism endangered or threatened when it is at a very high risk of dying out in the wild in the near future. Such species need urgent help, and ex situ conservation is then the desirable approach. The list helps governments decide which species need protection first.
What the IUCN Red List shows (textbook figures)
- 784 extinctions in the last 500 years: 338 vertebrates, 359 invertebrates and 87 plants. 27 species disappeared in the last twenty years alone.
- More than 15,500 species worldwide face the threat of extinction; the textbook's summary says more than 650 of them are from India.
- Share of species under threat: 12% of birds, 23% of mammals, 32% of amphibians and 31% of gymnosperms.
- Extinctions are not random: some groups, such as amphibians, appear more vulnerable.
- If present trends continue, nearly half of all species on Earth might be wiped out within the next 100 years.
Extra reading (not in your textbook): IUCN categories and Indian examples
The IUCN sorts species into categories: extinct, extinct in the wild, critically endangered, endangered, vulnerable, near threatened, least concern and data deficient. Critically endangered, endangered and vulnerable species are together called threatened. Older printed Red Data Books had pink pages for critically endangered species and green pages for species that had recovered. In India, the Botanical Survey of India and the Zoological Survey of India have prepared Red Data Books. The Great Indian Bustard and the gharial are listed as critically endangered, but statuses change, so check the latest list.
The Red List helps India decide which species need habitat protection or captive breeding first. (Extra reading: the Great Indian Bustard of Rajasthan's Thar, one of the rarest Indian birds, is now being bred in captivity.)
1 marks: “Name the organisation that maintains the Red List of threatened species.” The IUCN (International Union for Conservation of Nature and Natural Resources).
2 marks: “What is the Red Data Book? What does the IUCN Red List (2004) quoted in your textbook show about extinctions?” A record of species that are extinct or at risk of extinction, kept by the IUCN as its Red List. It records 784 extinctions in the last 500 years: 338 vertebrates, 359 invertebrates and 87 plants.
2 marks: “Distinguish between natural extinction and anthropogenic extinction.” Natural: slow loss due to environmental change over long periods, part of evolution. Anthropogenic: rapid loss caused by human activities such as habitat destruction and over-hunting.
Red List numbers: 784 lost in 500 years, 15,500 under threat, and amphibians (32%) the most at risk.