Ecological island

The definition does not include land within a fence erected to: The concept of mainland islands was pioneered in New Zealand and arose mainly from the particular circumstances of that country's history.

For millions of years New Zealand was part of the supercontinent Gondwanaland, which included Australia, Africa, and South America, and shared the same flora and fauna.

Birds, reptiles, plants, insects, and bats, all evolved in the absence of terrestrial mammals, and have little defence against alien species.

However, New Zealand also includes many offshore islands, some of which contained species rare or extinct on the mainland because introduced pests could not reach them.

[3] There are excellent projects where alien species numbers are kept down by various methods other than a pest-exclusion fence or the coastline, but these are not generally described as ecological islands.