The IUCN Red List at Higher Level: The same Red List as SL, with different species: the Hainan gibbon, the European hamster and the European eel. At HL, expect to outline the IUCN's criteria with their thresholds, such as 'a fall of more than 80% in three generations'.
Practise this as you read
- Match each fact about a species to an IUCN criterion.
- Quote a threshold or a number with every criterion.
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One global list: Every species can be given a conservation status. The IUCN assesses it and publishes the result as the IUCN Red List.
The points to remember
- A species' conservation status shows how close it is to extinction.
- Status is assessed globally by the IUCN: the International Union for Conservation of Nature.
- The results are published as the IUCN Red List of Threatened Species.
- Scientists, conservationists, governments and policymakers worldwide use it to set priorities.
Remember it as: Status = how close to extinction. IUCN decides; the Red List shows it.
Who uses the Red List
- Scientists and conservationists: to see which species need help most.
- Governments and policymakers: to write laws and decide where money goes.
- Everyone: it is free to search online, so anyone can check a species.
Real example: in 2021 the IUCN assessed Africa's two elephant species separately for the first time. The forest elephant was listed as critically endangered and the savanna elephant as endangered, so each now gets the attention its own risk needs.
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The IUCN does not guess. It uses precise criteria and data on five things the guide names.
The five things status is based on
- Number of individuals: how many are left, especially mature (breeding) adults.
- Rate of increase or decrease of the population, e.g. a fall of 80% in three generations.
- Breeding potential: how fast it can reproduce and recover.
- Geographic range: how large the area it lives in is, how many places, how fragmented.
- Known threats, such as habitat loss or hunting, which make a fall likely to go on.
Remember it as: How many, how fast, how fertile, how far, how threatened.
Real example: the Hainan gibbon lives in one reserve on Hainan Island, China (tiny range). About 2000 in the 1950s fell to fewer than 10 by 1980 (steep decrease); about 40 are left (tiny number). A female has one infant about every two years (low breeding potential). Forest clearing for rubber (known threat). So it is critically endangered.
Say it the IUCN way
- The precise IUCN criteria: population size, reduction in size, range (extent of occurrence, area of occupancy).
- Also: habitat fragmentation, habitat quality or loss, and the probability of extinction.
- Always say the size or the direction: 'fewer than 250 adults', 'decreased population', not 'population'.
- A threat on its own (hunting, predators, fire) is a cause, not a criterion: turn it into one, e.g. 'habitat loss'.
- Also accepted: trophic level (top predators are few to begin with) and genetic diversity.
Three answers that score nothing: 'Population' with no size or direction. 'Population density'. A threat alone, such as 'poaching' or 'predation by rats': say what it does, e.g. 'loss of habitat' or 'reduction in population size'.
The criteria place each species in one rank, from the lowest risk to the highest.
The points to remember
- Seven ranks from lowest to highest risk: LC, NT, VU, EN, CR, EW, EX.
- Threatened means vulnerable, endangered or critically endangered: VU + EN + CR.
- EW, extinct in the wild: it survives only in captivity or cultivation. EX: none left alive.
- DD, data deficient: not enough data to judge. NE: not yet evaluated.
- Each rank has precise thresholds, e.g. critically endangered: fewer than 250 mature adults and still falling.
- When the data change, a species moves up (uplisted) or down (downlisted) a rank.
| Rank | What it means |
|---|---|
| Least concern (LC) | Widespread and common |
| Near threatened (NT) | May become threatened soon |
| Vulnerable (VU) | High risk of extinction in the wild |
| Endangered (EN) | Very high risk |
| Critically endangered (CR) | Extremely high risk |
| Extinct in the wild (EW) | Survives only in captivity or cultivation |
| Extinct (EX) | No individuals remain alive |
Real example: the European hamster was once so common in Europe's wheat fields that it was a pest. As farms changed, its numbers and range shrank fast, and in 2020 it was moved up to critically endangered: a reduced range and a decreasing population.
| Criterion | Critically endangered when... |
|---|---|
| Population reduction | It fell by 90% or more in 10 years or three generations (80% if the causes have not stopped) |
| Small range | Extent of occurrence under 100 km², or area of occupancy under 10 km², and fragmented or in one place |
| Small, declining population | Fewer than 250 mature adults and still falling, or no group larger than 50 |
| Very small population | Fewer than 50 mature adults |
| Probability of extinction | At least 50% within 10 years or three generations |
A change needs a change word: Why did a species move up a rank? 'Its population decreased', 'its range was reduced', 'its habitat became more fragmented'. The word decreased, reduced or increased is what earns the mark.
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Red List data often come as a bar chart split into ranks, or as a graph of numbers over time.
The points to remember
- Add the three threatened bars: VU + EN + CR. Near threatened is not threatened.
- A percentage is part ÷ whole × 100; always write the % sign.
- Average annual change = change in numbers ÷ number of years.
- Read both values when asked for two years: both are needed for the mark.
- Data deficient groups are hard to survey: they move a lot, live in deep or vast oceans, hide, or few experts can identify them.
- A criterion must fit the data: if numbers are rising, 'declining' is wrong; say 'small population' or 'small range'.
Worked example (the chart above): cycads: 18% CR + 26% EN + 21% VU = 65% threatened. Freshwater crabs are 49% data deficient: few experts can tell the species apart, and many live in remote streams.
Give the reason, not just the problem: 'They are hard to find' or 'they migrate' alone is not enough. Say why: 'they migrate across whole oceans, so they cannot be counted in one place'.
How this comes up: Paper 1 (HL): a fact file on one species. Outline two criteria used to assess it as critically endangered [2].
Figure 1 is a fact file on the European eel.
With reference to Figure 1, outline two of the criteria used to assess the European eel as critically endangered.
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