Threat classification systems
The IUCN (or World Conservation Union) developed the IUCN Red List of Threatened Species™ over four decades ago. This classification system determines the relative risk of extinction of the world’s animal and plant species. Red List species are categorised as Least Concern, Vulnerable, Endangered, or Critically Endangered. Extinct species are also listed (Extinct and Extinct in the Wild). For wide-ranging species such as many New Zealand seabirds (e.g. albatross), this internationally-recognised classification system is of great value in focusing conservation management actions across country borders. However, its applicability to the New Zealand environment was questioned, and the first national-based classification system for New Zealand species was developed in 1992 which ranked species according to management priority (Molloy and Davis 1992).
This system was superseded in 2002 by the New Zealand threat classification system which assesses taxa according to threat of extinction (Molloy et al. 2002). This system had many differences from the IUCN system, but was designed to complement it. The system takes account of the relatively small size of New Zealand, and the large number of taxa with naturally restricted ranges and small population sizes. Notably, unlike the Red List, the New Zealand system not only classifies species, but also classifies subspecies, ‘forms’ and taxa which have not yet been assigned taxonomic status (e.g. newly-discovered plant or lizard species). It also classifies the New Zealand populations of species that are found in other countries (e.g. the white heron or kotuku is Nationally Critical in New Zealand as it numbers less than 200, but the species is expanding its range in many other parts of the world). New Zealand taxa were classified according to the categories and criteria set out in Molloy et al. 2002 in 2005 (Hitchmough 2007). Hitchmough et al. (2007) listed 2788 taxa as Threatened (i.e. from Sparse to Nationally Critical).
Figure 1: Structure of the New Zealand Threat Classification System (from Molloy et al. 2002)
In 2008, the classification system was revised and substantial changes made to some categories and criteria (Townsend et al. 2008). Leading experts in their respective fields are presently at various stages in the process of reclassification of New Zealand taxa. To date, classifications of birds and plants have been revised.
The most recent classification available is used on this website. This means that, at present, two systems are used in this website. Categories are broadly comparable, for example, the categories of Gradual Decline and Serious Decline in the old system are similar to Declining in the new system.
Figure 2: Revised New Zealand Threat Classification System (from Townsend et al. 2008)
Additionally, increasing information about certain species and/or successful conservation management actions have resulted in some species previously considered to be Threatened to be listed as Not Threatened in 2009 (e.g. kereru or woodpigeon). These species remain on the website for the sake of completeness.
Suggested reading (all available online)
de Lange P.J.; Norton D.A.; Heenan P.B.; Courtney S.P.; Molloy B.P.J.; Ogle C.C.; Rance B.D.; Johnson P.N.; Hitchmough R. 2004. Threatened and uncommon plants of New Zealand. New Zealand Journal of Botany 42: 45-76.
Hitchmough R.; Bull L.; Cromarty P. (Comps.). 2007. New Zealand Threat Classification System lists 2005. Department of Conservation, Wellington, New Zealand.
Miskelly C.M.; Dowding J.E.; Elliott G.P.; Hitchmough R.A.; Powlesland R.G.; Robertson H.A.; Sagar P.M.; Scofield R.P.; Taylor G.A. 2008. Conservation status of New Zealand birds, 2008. Notornis 55: 117-135.
Molloy J.; Bell B.; Clout M.; de Lange P.; Gibbs G.; Given D.; Norton D.; Smith N.; Stephens T. 2002. Classifying species according to threat of extinction. A system for New Zealand. Threatened Species Occasional Publication 22. Department of Conservation, Wellington. 26p.
Townsend A.J.; de Lange P.J.; Duffy C.A.J.; Miskelly C.M.; Molloy J.; Norton D.A. 2008. New Zealand Threat Classification System manual. Department of Conservation, Wellington, New Zealand.