How the status of species is assessed
The New Zealand Threat Classification System (NZTCS) assesses the conservation status of species according to the risk of extinction they face within New Zealand.
Most native species are considered to be ‘Not Threatened’ because their populations are sufficiently large and stable that there is little concern about their future. However, a significant number of species are undergoing or have experienced significant declines.
Species are assessed by panels of experts drawing from the New Zealand scientific community. The assessments use two very basic measures:
- population size (number of breeding adults or area of habitat occupied)
- population trend (rate of decline or increase).
For species with stable populations, whether or not they have declined historically is also taken into account.
These are species at greatest risk of extinction. They are either extremely rare, rare following severe historical decline, declining at an extremely high rate, or both uncommon and declining.
This broad ‘umbrella’ category is subdivided into three conservation status categories depending on the severity of risk they face:
- Nationally Critical
- Nationally Endangered
- Nationally Vulnerable
Nationally Critical species are at immediate risk of extinction. The others are at serious risk of extinction but are somewhat buffered by larger populations or lower rates of decline.
At Risk species
NZTCS categories for native species
Species in this category are not considered Threatened but could quickly become so if declines continue or if a new threat arises. At Risk species are either declining but not uncommon, or uncommon but not declining. The categories in this umbrella category are:
- Declining (population declining but still common)
- Relict (small population stabilised after declining)
- Naturally Uncommon (population is naturally small and, therefore, susceptible to harmful influences)
- Recovering (population is small but increasing after previously declining)
The relationships among these categories are summarised in this diagram on the right.
Other categories are:
- Migrant (native species that visit regularly but do not breed here)
- Vagrant (native species that visit only irregularly and/or in very small numbers and do not breed here)
- Coloniser (species that are uncommon because they are recent arrivals but have arrived and established without human assistance)
- Introduced and Naturalised (species that arrived by human agency and are reproducing in the wild in New Zealand)
- Data Deficient (species that are too poorly known for an assessment to be possible)
Difference between threatened and protected species
In many countries, when species are listed as threatened, they automatically also receive legislative protection from hunting, habitat destruction and other threats. In New Zealand this is not true – there is no direct link between conservation status as assessed using the NZTCS (or IUCN red-list) and legal protection.
Legal protection for native plants and animals exists via the:
- Conservation Act 1987 (plants and animals on public conservation land only)
- Marine Mammals Protection Act 1978 (marine mammals only)
- Wildlife Act 1953 (animals only; originally terrestrial vertebrate animals only, but a few invertebrate and marine fish species are declared to be “animals” for the purposes of the act)
Terrestrial vertebrate animals are completely protected under the Wildlife Act unless they are specifically excluded or the degree of protection limited in one of the schedules to the Act.
Marine Mammals are completely protected under the Marine Mammals Act.
Plants, invertebrates and fish are generally not protected except where they occur in national parks or reserves. Exceptions are the few fish and invertebrates deemed to be animals under the Wildlife Act.
The Native Plants Protection Act 1934 allows for the national or regional protection of a native plant species by a Warrant issued by the Governor-General, but does not infer any general protection of native plants outside national parks and reserves.
The schedules to the Wildlife Act 1953 are reviewed from time to time and may be changed by order in council.
The New Zealand Threat Classification System series are lists providing the conservation status of a plant or animal group. There are 23 groups and each group is assessed once every 3 years.
View the NZTCS series
Threatened: likely to go extinct (or be reduced to a few small safe refuges) within the lifetime of those alive today.
Nationally Critical: most severely threatened subset of Threatened species; facing immediate high risk of extinction
Nationally Endangered: second subset of Threatened species; facing high risk of extinction in the short term
Nationally Vulnerable: third subset of Threatened species; facing risk of extinction in the medium term
At Risk: species which are not considered Threatened but could quickly become so if declines continue or if a new threat arises. At Risk species are either declining or uncommon but not both.
Declining: subset of At Risk; population declining but still common
Relict: subset of At Risk; small population stabilised after declining
Naturally Uncommon: subset of At Risk; population is naturally small and, therefore, susceptible to harmful influences
Recovering: subset of At Risk; population is increasing after previously declining
Migrant: native species that visit regularly but do not breed here
Vagrant: native species that visit only irregularly and/or in very small numbers and do not breed here
Coloniser: species that are uncommon because they are recent arrivals but have arrived and established without human assistance
Introduced and Naturalised: species that arrived by human agency and are reproducing in the wild in New Zealand
Data Deficient: species that are too poorly known for an assessment to be possible
Protected species: species for which deliberate killing or capture is prohibited by act of parliament (Wildlife Act 1953 or Marine Mammals Act 1978)
Partially Protected species: species which are protected in most circumstances but for which deliberate killing or capture is permitted in some specific circumstances under the Wildlife Act 1953