Ecological Island

Encyclopedia : E : EC : ECO : Ecological Island

Contents

1 Definition
2 Background
3 Offshore Islands
4 Ecological Islands
5 See also

Definition

An Ecological Island is not necessarily an island surrounded by water, but is an area of land, isolated by natural or artificial means from the surrounding land, where:

a natural micro-habitat exists amidst a larger differing ecosystem,
all non-native species (at least predator species) have been eradicated,
native species are reintroduced and nurtured,
the natural or artificial border is maintained to prevent reintroduction of non-native species.

In addition, there is usually provision for controlled public access, and scientific study and research.

The ultimate goal is to recreate an ecological microcosm of the country as a whole as it was before human arrival.

The definition does not include land within a fence erected to:

protect farm animals from wild predators
protect a specific species from specific predators
exclude farm animals only
exclude native animals (although some native animals, weka for example, may need to be excluded during a species' recovery phase)

Background

The concept 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. About 70 million years ago New Zealand became separated, earlier than Australia, South America and Antarctica. About five million years later dinosaurs became globally extinct leaving the way open to mammals to dominate - except in New Zealand where there were no land mammals (only bats and seals). In the absence of mammals, birds became dominant. Evolutionary processes resulted in a unique assemblage of plants and animals, and New Zealand became a land dominated by birds. Without competition from browsing mammals, birds evolved to occupy niches that mammals occupied elsewhere. Threatened by few predators many birds had no need to fly and became flightless. Birds, reptiles, plants, insects, and bats, all evolved in the absence of mammals, and have little defence against alien species.

With human colonisation came many accidental or deliberate introductions of mammals and birds. These wrought havoc with native species and many became extinct, many others were reduced in range and number, with some teetering on extinction.

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.

Offshore Islands

Increasingly over the last hundred years, New Zealand's Department of Conservation together with many volunteers have developed and perfected world-first methods of clearing some of these islands of all introduced pests, and island restoration, creating safe havens for the reintroduction of at-risk species, thereby saving them from extinction. These islands are also used to expand the range of rare species so that an ecological disaster on one island would not result in the total extinction of a species. As many species rebound in numbers in the absence of predators the islands act as species reservoirs enabling the periodic removal of some to create breeding colonies on other cleared islands, or on the mainland itself.