New Zealand's offshore islands
What islands do we have?
The Department of Conservation manages or has an interest in approximately 220 islands (larger than 5ha in size) and numerous small islets and rock stacks. These include:
- 21 island groups (e.g. Poor Knights group (Northland), Mercury Islands (east of Coromandel Peninsula), Chetwode Islands (Marlborough Sounds), Auckland Islands (subantarctic);
- 11 islands that are partly reserve (eg D'Urville Island, Kapiti Island, Great Barrier Island);
- 8 inland freshwater island reserves (eg Mou Tapu and Mou Waho Islands in Lake Wanaka);
- 42% are nature reserves because of their outstanding biological values. A permit is required to visit these islands;
- Only a few islands are connected to marine reserves (eg Poor Knights Marine Reserve).
View a map of New Zealand's offshore islands.
Pest-free
Because islands can be made free from pests, they are good places for caring for threatened species which can no longer live on the mainland. For example, South Island saddlebacks were introduced to Kaimohu and Pohotairea Islands in the 1960s. Offspring from those birds are now on nine other islands!
Removal of pests can create spectacular plant regrowth and abundance of birds, lizards and insects. For example on Tiritiri Matangi Island there is now a carpet of regenerating seedlings following the eradication of kiore (Pacific rat) in 1993.
Where pests have been removed, the regeneration of the island often needs a helping hand. Conservation and community groups play an important role in replanting trees and shrubs to kick-start natural healing and to provide food sources for birds and insects.
As knowledge and technology improves, so does our ability to remove pests from larger islands. For example, by developing rat eradication techniques on small islands such as Burgess Island (159ha) and Tiritiri Matangi Island (196ha) we were able to plan for removal of kiore from Codfish Island (1396ha) to protect indigenous ecosystems and kakapo.
The water that surrounds islands acts as a moat, keeping threats away. As a result, some islands around New Zealand have few introduced pests or weeds and have relatively intact habitats. Many of these islands are nature reserves.
Vegetation on the wet western slopes,
Maud Island
Isolation of islands from the mainland has allowed evolution of some plants and animals found only on islands, (such as the Poor Knights lily and Campbell Island teal).
Islands have protected species from extinction. Tuatara and Whitaker's skink were once widespread in New Zealand, and are now found only on islands because on the mainland pests have wiped them out.
Where pests have got to an island, the water barrier makes it harder for them to re-invade once removed. For example, rats cannot usually swim the distance back from the mainland to the island.
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