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In the previous lesson, you explored how human activities threaten biodiversity through direct and indirect impacts, and how invasive alien species can reduce local biodiversity. This lesson asks a different question: how do we decide which species are most at risk, and who is responsible for saving them?
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3.2.4 The global conservation status of species is assessed by the International Union for Conservation of Nature (IUCN) and is published as the IUCN Red List. Status is based on number of individuals, rate of increase or decrease of the population, breeding potential, geographic range and known threats.
Precise criteria and data are used to assign status to a species, and a sequence of conservation status ranks have been defined from least concern (LC) to extinct (EX).
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The International Union for Conservation of Nature (IUCN) was founded in 1948. It is the global authority on the status of the natural world and the measures needed to safeguard it.
The IUCN Red List of Threatened Species
The IUCN publishes the Red List of Threatened Species, a comprehensive inventory of the global conservation status of species. The Red List currently includes over 160,000 assessed species. It uses precise criteria and data to assign a conservation status rank to each species. This is not a matter of opinion; it is a systematic, evidence-based process.
A sequence of conservation status ranks has been defined, from Least Concern (LC) to Extinct (EX). The full sequence is:
| Rank | Meaning |
|---|---|
| Not Evaluated (NE) | Has not yet been evaluated against the criteria |
| Data Deficient (DD) | There is inadequate information to make an assessment |
| Least Concern (LC) | Widespread and abundant; lowest risk of extinction |
| Near Threatened (NT) | Does not currently qualify as threatened, but is close to qualifying or likely to in the near future |
| Vulnerable (VU) | Facing a high risk of extinction in the wild |
| Endangered (EN) | Facing a very high risk of extinction in the wild |
| Critically Endangered (CR) | Facing an extremely high risk of extinction in the wild |
| Extinct in the Wild (EW) | Known only to survive in cultivation, captivity, or as a naturalised population well outside its past range |
| Extinct (EX) | No reasonable doubt that the last individual has died |
Note that NE and DD are not threat ranks; they indicate gaps in knowledge. The ranks from LC through to CR represent an increasing risk of extinction.
The IUCN assigns conservation status based on five criteria. These are the exact terms used in the IB syllabus:
For example, a species is classified as Critically Endangered if its population has declined by more than 80% over three generations, or if it has fewer than 250 mature individuals. These are quantitative thresholds, not subjective judgements.
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3.2.5 Assigning a global conservation status publicises the vulnerability of species and allows governments, non-governmental agencies and individual citizens to select appropriate conservation priorities and management strategies.
Include differences between the perspectives of governments, agencies and individuals in conservation.
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The Red List is not just a scientific database. By publicising the vulnerability of species, it provides the evidence base that allows governments, non-governmental agencies and individual citizens to select appropriate conservation priorities and management strategies.
However, these three groups may use the same data to arrive at different priorities, depending on their perspective and values.
| Stakeholder | How they use the Red List | Potential tensions |
|---|---|---|
| Governments | Draft legislation, designate protected areas, allocate funding, fulfil international treaty obligations (e.g. CBD, CITES) | May prioritise economically valuable species or politically convenient targets; constrained by budgets and competing national interests |
| Non-governmental agencies | Set campaign priorities, target fundraising, direct fieldwork, lobby governments for policy change | May focus on charismatic species that attract donations rather than ecologically critical but less photogenic species |
| Individual citizens | Make consumer choices (e.g. sustainable seafood), support campaigns, participate in citizen science, donate to conservation organisations | May lack scientific knowledge to assess priorities; influenced by media coverage and emotional appeal rather than ecological importance |
The key point is that the same data can lead to different conservation priorities depending on perspective and values. This links back to the environmental value systems you studied in Topic 1.1.