Level: SL and HL: Subtopic 3.2 Human impact on biodiversity
The International Union for Conservation of Nature (IUCN) assesses a species using evidence about its population, distribution, reproduction and threats. It applies standardized criteria to place the species in an IUCN Red List conservation category representing its global extinction risk.
How the Assessment Works
Scientists compile field-survey, monitoring, satellite, research and expert data. Evidence is evaluated against quantitative Red List criteria and reviewed before publication.
| Factor assessed | Why it matters |
|---|---|
| Number of individuals | Small populations are vulnerable to disease, environmental change and loss of genetic diversity. |
| Rate of population increase or decrease | A rapid or continuing decline raises extinction risk even if the population remains large. |
| Breeding potential | Low reproductive rates or limited breeding success reduce the species' ability to recover. |
| Geographic range | A small, fragmented or declining range increases vulnerability to habitat loss and local disturbance. |
| Known threats | Habitat destruction, overexploitation, invasive alien species, pollution, disease and climate change increase extinction risk. |
The resulting categories include Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild and Extinct. Data Deficient indicates insufficient evidence for assessment; it does not mean the species is safe.
The giant panda was reclassified from Endangered to Vulnerable after evidence showed population recovery, although habitat fragmentation remains a threat. Red List classifications can change when populations, threats or evidence change.
A common misconception is that the IUCN simply counts animals. In reality, it combines population size with trends, range, reproductive capacity and threats to estimate global extinction risk.
Exam Technique
For an explain question, link each factor to extinction risk rather than merely listing criteria. For an evaluate question, note that standardized categories support conservation priorities, but limited data, uncertainty and differences between global and local conditions can affect an assessment.
