The Department of Conservation looks after about 220 offshore islands, including New Zealand's subantarctic islands, and numerous small islets and rock stacks. Offshore islands that are predator and pest-free are treated as havens or sanctuaries for New Zealand's vulnerable native species. Water surrounding offshore islands protects from invasions of introduced species that hunt or compete with natives. As a result, many offshore islands have few or no introduced pest species and relatively intact.
Some islands are home to animals and plants that have become extinct on the mainland.
Islands are also easier to eradicate pest species from as reinvasion is less likely with a water boundary than on mainland sites. People can visit most offshore islands, although permits are required to visit some sensitive and special islands. Check with the relevant Department of Conservation office to see if you need to apply for a permit.