Never Never isLand: the definition of island
The definition of island (such as the definition of cave, mountain, valley, river, lake, river island...) is strongly linked to an anthropocentric concept, which does not really apply to Nature. This concept should NOT be related to Earth as it is, but to the representation that we need to make of it.
It, at once, follows that an absolute definition of (marine) island really does not exist.
From a physio-geographical and geomorphological point of view, the island is a portion of the Earth's surface (made by any lithotype, or sand, clay, ice) generally located above the average sea level (asl). It bears a well-defined and closed cartographic boundary, regardless of its size and context where the island is located.
|Map of Neverland created by Walt Disney Productions|
as a promotion for its 1953 film Peter Pan.
For Biology, the island is a portion of the terrestrial environment not directly connected to other terrestrial environments. The variability of the shoreline in biology is resolved by considering the supralittoral plan as marine and not emerged, although it might only temporary be subject to the waves effects or being wet by aerosol and sprays. If the peace of rock is a stack of 20 m, where the supralittoral biocenosis disappear, then this is called island.
From an ecological point of view - Ecology as a science that studies how the life systematically occupies the space - the concept and definition of "island" is functional to how life occupies the portion of the Earth's surface surrounded by the sea.
From a geopolitical and juridical point of view (according to the Law of the Sea United Nations - UNCLOS - the International Convention of Montego Bay, 1982), the island is a natural extension of land surrounded by the sea, which remains emerged during the maximum tide, and with a size that allows drawing a line attributable to the territorial waters limit. A small natural rock is defined as a portions of land not suitable for permanent human settlements or capable of economic activities, therefore, they are not taken into account for the purpose of delimiting the territorial sea.
It seems that at the basis of the definitions of island and little rocks for the military Institutes, there is an internationally adopted and not better defined concept of "self-sustainability". According to this concept, the island is "a piece of land that can ensuring livelihood regardless of his physical size. A sea rock, in its strict sense is, indeed, a rock formation or corallifera, thus not suitable for self-sustenance". (An immediate question arises: self-sustaining for plant communities, communities of animals, a man or a human community?)
In the specific case of the Italian Small Island Information System I am realising (still in progress), the reference definition is the geo-physical and morphological one, less the cartographic and administrative definition.