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Why are islands special?

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.
Isolation of islands from the mainland has allowed evolution of some
plants and animals found only on islands, (such as the Poor Knights lily.)

Islands have protected species from extinction. Tuatara  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.

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 (eg 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).

What impact do
animal pests
have?


Pests such as stoats and wild cats eat nesting birds and chicks. Rats have
a wide diet of lizards, birds, chicks, insects and seeds. Possums are
known for their ability to eat foliage and have been known to eat bird
eggs and kill birds protecting their nests.
New Zealand's flora and fauna evolved in the absence of mammalian
predators and herbivores and are poorly equipped to survive in their
presence. 44 birds have become extinct since the arrival of pests in New
Zealand with human colonisation.
Analysis of the stomach contents of stoats and rats has confirmed that
native species are part of their diet. Videos have captured possums
eating eggs. Where pests have been removed, the increase in native plant
and insect life shows the effect the pests have had.

Pest-free!

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.

Department of Conservation fact sheet on offshore Islands.