An ecological island
is not necessarily an island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
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
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
Also, in artificial ecological islands (also known as mainland islands
- all non-native species (at least predator species) have been eradicated,
- native species are reintroduced and nurtured, and
- the natural or artificial border is maintained to prevent reintroduction of non-native species.
The ultimate goal is to recreate an ecological microcosm of the country as a whole as it was before human arrival. There is usually provision for controlled public access, and scientific study and research.
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
The Weka or woodhen is a flightless bird species of the rail family. It is endemic to New Zealand, where four subspecies are recognized. Weka are sturdy brown birds, about the size of a chicken. As omnivores, they feed mainly on invertebrates and fruit...
for example, may need to be excluded during a species' recovery phase).
The concept of mainland islands was pioneered in New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
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
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, and South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, and shared the same flora
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
. About 70 million years ago New Zealand became separated, earlier than Australia, South America and Antarctica. About five million years later dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s became globally extinct leaving the way open to mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s to dominate - except in New Zealand where there were no land mammals (only 3 species of bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s and seals
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
). In the absence of mammals, bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s 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 many species became flightless. Birds, reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s, plants, insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, 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. Traditionally pacific rats (Rattus exulans
), Norway rats (Rattus norveigucus
), ship rats (Rattus rattus
) cats, ferrets, stoats, and weasels were all considered to be the main culprits in the decline of native species of New Zealand birds, reptiles and insects. More recent information adds hedgehogs and mice to the list. These species have been introduced for a variety of reasons and some inadvertently. The effect remains the same: they have all contributed to the decline of native animals. Possums and deer did the same for the forest.
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.
Increasingly over the last hundred years, New Zealand's Department of Conservation
The Department of Conservation , commonly known by its acronym, "DOC", is the state sector organisation which deals with the conservation of New Zealand’s natural and historic heritage...
together with many volunteers have developed and perfected world-first methods of clearing some of these islands of all introduced pests, and island restoration
The ecological restoration of islands, or island restoration, is the application of the principles of ecological restoration to islands and island groups. Islands, due to their isolation, are home to many of the world's endemic species, as well as important breeding grounds for seabirds and some...
, 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.
Following the example of what had been achieved on offshore islands, groups of New Zealanders decided to create artificial ecological islands on the mainland so that the public could have easier access and learn what New Zealand looked and sounded like before human colonisation. There are excellent projects where alien species numbers are kept down by various methods other than a pest-exclusion fence
thumb|280px|Xcluder pest-exclusion fence around perimeter of [[Maungatautari Restoration Project|Maungatautari]]A pest-exclusion fence is built to exclude certain types of animal pests from an enclosure...
or the coastline, but these are not generally described as ecological islands.
Projects that do meet the criteria, or are aiming to, include:
- New Zealand
- Glenfern Sanctuary Charitable Trust
- Karori Wildlife Sanctuary
Zealandia, formerly known as the Karori Wildlife Sanctuary, is a protected natural area in Wellington, New Zealand, where the biodiversity of 225 ha of forest is being restored...
- Karori Wildlife Sanctuary Trust
- Maungatautari Restoration Project
The Maungatautari Restoration Project is the largest ecological restoration project in New Zealand, located near Cambridge in the Waikato region in the central North Island of New Zealand....
- Maungatautari Ecological Island Trust
- Moehau Environment Group
- Orokonui Ecosanctuary
Orokonui Ecosanctuary, called Te Korowai o Mihiwaka in Māori, is an ecological island wildlife reserve being developed by the Otago Natural History Trust in the Orokonui Valley near Waitati, New Zealand, 20 km to the north of central Dunedin....
- Orokonui Ecosanctuary
- Tawharanui Open Sanctuary
Tawharanui Peninsula is a finger of land projecting into the Hauraki Gulf from the east coast of the much larger North Auckland Peninsula of New Zealand. It separates Omaha Bay to the north from Kawau Bay and Kawau Island to the south...
- Tawharanui Open Sanctuary Society
- The Brook Waimarama Sanctuary (external website)
- Brook Waimarama Sanctuary
The Brook Waimarama Sanctuary is a 700 hectare mainland “ecological island” sanctuary located in Nelson, New Zealand. It was created in 2004 with the intent of restoring the local populations of pre-European flora and fauna which have been ravaged by introduced mammalian predators. Invasion by...