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  • 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.

    Rights: The University of Waikato Te Whare Wānanga o Waikato

    An Archey’s frog

    A number of Archey’s frogs have been successfully cured of chytridiomycosis in the lab. Archey’s frogs are critically endangered, so this is an important step in their conservation.

    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 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 1st 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.

    Rights: ICUN

    IUCN red list

    The IUCN Red List of Threatened Species™ is an internationally recognised system for evaluating conservation status. The list aims to help prioritise the species that most urgently need conserving and to provide a global biodiversity index.

    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.


    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.


    When the best available evidence indicates that the species faces a very high risk of extinction in the wild.


    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.

    Conservation rankings

    Dr Phil Bishop talks about our native frogs and some of the reasons they are so vulnerable to extinction. He describes the process of assigning a conservation ranking or threat status to a species.

    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.

    The New Zealand system was revised in 2007, and some of the categories were changed as a result. The revised system is divided into the following groups:

    Threatened species

    • Nationally critical
    • Nationally endangered
    • Nationally vulnerable

    At-risk species

    • Declining
    • Recovering
    • Relict or naturally uncommon

    Introduced species

    • Migrant
    • Vagrant
    • Coloniser

    Species that do not fit into any of these categories

    • Data deficient
    • Extinct
    • Not threatened

    Useful links

    The Department of Conservation electronic atlas for amphibians and reptiles gives the New Zealand threat classification and IUCN threat status for our native reptiles and amphibians.

    Visit the IUCN website for detailed information about each category on the Red List and to search for the latest international conservation rankings.

    Additional information about the New Zealand Threat Classification System in the manual published by DOC.

    See the New Zealand Herpetological Society (NZHS) website, it has comprehensive and freely available online resources about Aotearoa New Zealand’s reptiles and amphibians.

    Read The Guardian article New IUCN green status launched to help species ‘thrive, not just survive’

      Published 12 January 2010, Updated 29 July 2021 Referencing Hub articles
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