The International Union for the Conservation of Nature has a ranking system for threatened species. Many countries also have their own systems.
New Zealand’s system
In 2002, conservationists created a New Zealand-specific system for classifying threatened species. It can be used for all New Zealand life forms, including marine species. The ranking depends on conservation status, threats to survival, whether they are endemic, vulnerability and cultural importance. There are eight rankings, from the most to the least threatened:
- nationally critical
- nationally endangered
- nationally vulnerable
- serious decline
- gradual decline
- range restricted
- data deficient.
New Zealand has one of the highest rates of threatened native species in the world. For example, 34% of plants are considered to be at some level of risk, and 37% of the 215 native birds are listed as threatened by the International Union for the Conservation of Nature.
Numbers of threatened species
A 2002 survey classified a total of 2,372 species (including 312 subspecies) as threatened. This included bats, birds, bryophytes (mosses, liverworts and hornworts), freshwater fish and invertebrates, frogs, fungi, macro algae, marine fish, marine mammals, reptiles, land invertebrates and vascular plants.
Between 1860 and 1970, at least 150,000 kea (alpine parrots) were killed. This figure is based on a bounty offered to kill the birds, which were believed to attack sheep, causing blood poisoning, and drive flocks over cliffs. In 2021 there were as few as 3,000–7,000 kea left.
By 2007 the number of threatened species had increased to 2,788. This was mostly due to better information on many that were once classed as ‘data deficient’.
Scientists know a lot about the more charismatic species – those that are large, attractive, odd, or rare. Little is known about less visible species. Only bats, birds, and frogs have been described and understood well enough to be assigned a status with some confidence.
Less understood species
Many species fall into the ‘data deficient’ category. Scientists may suspect they are in danger, but have little information – 1,455 species and subspecies of fungi belong in this group.
Although 30,000 native New Zealand species have so far been identified and named, there are possibly a further 50,000 that are as yet unidentified. Most of these are insects, worms, fungi, or micro-organisms such as algae. Some of these may be threatened, and some may have already been lost without ever being scientifically described.
It is difficult for the Department of Conservation to decide where to spend its limited funds. Many questions arise. Which species are actually at risk of extinction? Can the risk be measured? Even if enough information exists to answer these questions, trade-offs have to be made.
In 1990 the Department of Conservation and other groups set up the Threatened Species Trust Programme to attract commercial sponsorship. This has generated more funds for saving threatened species. For example, between 1990 and 2004 the aluminium smelting company Comalco donated $1.6 million towards saving the kākāpō. The Bank of New Zealand has been a multi-million-dollar sponsor of efforts to save the kiwi since 1991.