Ranking species according to their risk of extinction is an important tool in conservation management. The Department of Conservation (DOC) spends almost 15% of its total budget on species conservation. Additional money is spent on related programmes, including the control of introduced species, mainland islands and fire control.
Conservation rankings help DOC to prioritise which species most urgently require action to prevent extinction. They can then allocate the budget according to these priorities.
There are 2 major ranking systems recognised in Aotearoa New Zealand – the IUCN Red List categories and the New Zealand Threat Classification System.
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN) was founded in 1948 as the world’s first global environmental organisation. The IUCN aims to support and promote conservation initiatives worldwide. A major aspect of their work is assessing the conservation status of different species and assigning rankings to help prioritise conservation actions.
The IUCN Species Survival Commission manages this work, and the rankings are published in the IUCN Red List of Threatened Species™. The Red List ranks species according to their threat of extinction – these ranking categories are recognised internationally.
| Extinct | When there is no reasonable doubt that the last individual has died. |
| Extinct in the wild | When the species is known only to survive in captivity. |
| Critically endangered | When the best available evidence indicates that the species faces an extremely high risk of extinction in the wild. |
| Endangered | When the best available evidence indicates that the species faces a very high risk of extinction in the wild. |
| Vulnerable | When the best available evidence indicates that the species faces a high risk of extinction in the wild. |
| Near threatened | When the species does not qualify for ‘critically endangered’, ‘endangered’ or ‘vulnerable’ status now, but is close to qualifying or is likely to qualify in the near future. |
| Least concern | When the species does not qualify for any of the above rankings. The species may be widespread. |
| Data deficient | When there is not enough information available to make a satisfactory assessment. |
| Not evaluated | When a species has not yet been evaluated. |
The process of assigning rankings is very detailed and is based on scientific evidence. Thousands of scientists around the world are involved in the process. Information used to make an assessment includes distribution of the species, habitat preferences, major threats, conservation measures and population size estimates. The paperwork is standardised, and there is an appeal process in case of a disagreement over a ranking.
In 2021, IUCN launched a new global standard known as the IUCN Green Status of Species. The standard uses a species' historical population size, current distribution, success of ongoing conservation efforts and viable habitat to create a fuller picture of the species' conservation status.
Nature of science
Assigning a conservation ranking to a species is an important process that requires input from a number of scientific experts. Rankings are not fixed and may change as new information becomes available.
New Zealand Threat Classification System
The New Zealand Threat Classification System was first developed in 2002 and is used to rank our native species according to the threat of extinction. It was designed to complement the IUCN system and is tailored to New Zealand’s unique ecology.
The Department of Conservation (DOC) manages the system, and panels of experts who have specialist knowledge about a particular species carry out the rankings process. These experts use a flowchart to determine the most appropriate ranking and consider various factors including whether or not the species is endemic, whether the species breeds in New Zealand and whether there are any threats to the species’ habitat.
Revised manuals of the New Zealand Threat Classification System were published in 2008 and 2022. Some of the categories were changed as a result. The revised system is divided into the following groups:
Threatened species
- Nationally critical – most severely threatened, facing an immediate high risk of extinction
- Nationally endangered – facing high risk of extinction in the short term.
- Nationally vulnerable – facing high risk of extinction in the medium term.
- Nationally Increasing – small but increasing population still facing a risk of extinction in the medium term.
At-risk species
- Declining – population declining but still moderately common.
- Uncommon – population increasing after previously declining.
- Recovering – naturally or unnaturally small population and therefore susceptible to harmful influences. Uncommon is the conservation status that combined the 2008 conservation statuses Relict and Naturally Uncommon.
Introduced species
- Migrant
- Vagrant
- Coloniser
Species that do not fit into any of these categories
- Data deficient
- Extinct
- Not threatened
Relationship of the NZTCS categories
This diagram shows the Zealand Threat Classification System (NZTCS). The conservation status of a species is a forecast based on observed trends and likely pressures. Panels of experts from New Zealand’s scientific community work together to determine a species' conservation status.
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Related content
What does it really mean if a species becomes extinct, for example, the huia.
Find out more about the work being undertaken in Aotearoa New Zealand to protect our endemic species.
Activity ideas
Conservation ranking in action explores the processes and criteria used to rank animals according to their conservation threat status.
Ethics in conservation science encourages students to consider the conservation of native frogs from a number of different perspectives.
Useful links
Visit the IUCN website for detailed information about each category on the Red List and to search for the latest international conservation rankings.
Read The Guardian article New IUCN green status launched to help species ‘thrive, not just survive’.
View the Conservation status of plants and animals on the DOC website and additional information about the New Zealand Threat Classification System in the manual published by DOC.
See the Stats NZ Tatauranga Aotearoa website for more information on the Extinction threat to the indigenous species of Aoteraroa.
For information on the conservation status of a species search the NZTCS database.
The electronic atlas for amphibians and reptiles from the Department of Conservation (DOC) gives the New Zealand Threat Classification and IUCN threat status for our native reptiles and amphibians.
See the New Zealand Herpetological Society (NZHS) website, it has comprehensive and freely available online resources about Aotearoa New Zealand’s reptiles and amphibians.
