Ex situ conservation, the Red Data Book and the IUCN… | StemPy Lab
Course 31.3·Lesson 2 of 3
Ex situ conservation, the Red Data Book and the IUCN categories
When a species cannot survive in the wild, we keep it outside its habitat. This lesson explains ex situ conservation with zoos, botanical gardens, seed banks and cryopreservation, and the IUCN Red List, with its categories from Extinct to Least Concern.
about 25 min1 simulation1 practice question
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Try the code and the simulations beside the lesson.
A last resort
Think of a species with only a few animals left, in a forest that is shrinking. In situ protection may not be enough. Then people take some of the animals or seeds out of the habitat and keep them safe. This is ex situ conservation.
Methods of ex situ conservation
NCERT lists these methods.
Zoological parks, botanical gardens and wildlife safari parks. Threatened animals and plants are kept and bred in places that people look after. They are also places where people can learn.
Cryopreservation. The gametes of threatened species are stored in a viable and fertile condition at very low temperatures. The usual store is liquid nitrogen at about minus 196 degrees Celsius. Eggs can later be fertilised in vitro by IVF.
Tissue culture. Plants can be grown again from small pieces of tissue.
Seed banks. Seeds of wild and cultivated plants are dried and kept cold for a long time.
Ex situ conservation saves the species, but not its habitat or its web of life. That is why it works best with in situ conservation, and not alone.
How long can a seed wait?
A seed bank is a store, not a forever place. Seeds slowly lose their power to germinate. This part is not in the NEET syllabus, but A-Level and IB teach seed bank management. The sample is grown out to make fresh seed before its viability falls too low.
The model below uses a half-life. Every half-life, the share of viable seeds is halved. It is a model for practice, and each species has its own real rate.
A graph of the per cent of seeds that can germinate against the years in storage, from 0 to 100 years, for a model seed bank. Three curves start at 98 per cent. The red curve, with a half-life of 30 years, falls fastest. The green curve, with a half-life of 60 years, falls more slowly. The blue curve, with a half-life of 120 years, falls slowest. A dashed horizontal line marks the limit of 85 per cent.
The Red Data Book and the IUCN Red List
How do we know which species are in danger? A group called the IUCN (the International Union for Conservation of Nature) keeps a record of species that face the threat of extinction. This record is the Red Data Book, which is now published as the IUCN Red List. It is the source of the figures that NCERT gives for the threatened species.
The Red List sorts species into categories by the risk of extinction.
Extinct (EX): no individual is left.
Extinct in the Wild (EW): alive only in zoos, gardens or other places that people keep.
Critically Endangered (CR): an extremely high risk of extinction in the wild.
Endangered (EN): a very high risk.
Vulnerable (VU): a high risk.
Near Threatened (NT): close to threatened.
Least Concern (LC): at a low risk.
Two more are Data Deficient and Not Evaluated.
The three categories CR, EN and VU together are the threatened species.
A ladder of seven coloured bars under the title categories of the IUCN Red List, from most to least at risk. From the top: Extinct (EX) in black, Extinct in the Wild (EW) in dark grey, Critically Endangered (CR) in red, Endangered (EN) in orange, Vulnerable (VU) in yellow, Near Threatened (NT) in light green and Least Concern (LC) in green. A bracket marks CR, EN and VU as threatened. A line below says that Data Deficient and Not Evaluated are also categories, and are not ranked by risk.
The category of a species changes when it is assessed again. So a NEET question tests the meaning of the categories, and not the category of a named species. The detail of the categories is standard IUCN knowledge. NCERT does not list them in this chapter.
Try it in Python
The program uses the model to find the viability after some years and the time to grow out a sample.
Practise with new numbers
Common mistakes
Calling a zoo in situ. A zoo is outside the habitat, so it is ex situ.
Confusing Extinct and Extinct in the Wild. The second still has living individuals, but only in human care.
Putting Near Threatened among the threatened. Only CR, EN and VU are called threatened.
Saying that a seed bank stores seeds for ever. The seeds lose viability, and samples must be grown out.
Remember these
Ex situ: zoological parks, botanical gardens, wildlife safari parks, cryopreservation of gametes, tissue culture, seed banks.
The Red Data Book is the record of threatened species kept by the IUCN. It is now the Red List.
Categories from the highest risk: Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern.
Threatened means Critically Endangered, Endangered or Vulnerable.
Check yourself
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
Name three ex situ methods of conservation.
What is stored in cryopreservation, and in what condition?
What is the Red Data Book?
Which categories are called threatened?
How is Extinct in the Wild different from Extinct?
References
NCERT (2023). Biology, Textbook for Class XII, chapter 13, Biodiversity and Conservation, section on how do we conserve biodiversity.
IUCN (2012). IUCN Red List Categories and Criteria, version 3.1, second edition.