Island environments are terrestrial ecosystems that remain isolated from the continent by the sea, and whose boundaries are perfectly defined by the coastline, a characteristic that defines their isolation from the continents. This isolation, in the short or long term, made it possible for phenomena related to the greater simplicity of the ecosystems and the difficulty or impossibility that the species settled there have to carry out genetic exchange with the continental species, which present populations much more extensive, diverse and interconnected.
Broadly speaking, the islands can be divided according to their geological origin between the so-called continental islands and the oceanic ones. The continental islands may have their origin in ancient continental drift phenomena, which make up the so-called microcontinents, or be made up of spaces near the continental coast, whose insular origin is linked to oscillations in the sea level, so that they have been functioning alternately as islands or as a continent throughout the Pleistocene. Within LIFE INSULAR, this group includes the archipelagos located in the European Atlantic region.
On the contrary, the oceanic islands are linked to the volcanic activity of the seabed, they present a greater degree of isolation and therefore, in general, a greater degree of relictualism and endemicity, both due to the greater isolation and the absence of a biota. initial. The islands of the Macaronesian region included in the LIFE INSULAR project are included in this type of island.
Despite the fact that they only represent a small percentage of the earth's emerged surface, insular spaces are home to an important part of the planet's biodiversity, so that they form ecosystems with exceptional natural wealth. Not only the emerged part of the islands has high biodiversity values, the marine areas make up a mosaic of habitats that support a great diversity of flora and fauna species. Both the terrestrial and marine environments present a great singularity and fragility, exposed to damage derived from human activities.
In recent decades, the high tourist and fishing pressure and the presence of invasive species have led to the extinction or endangerment of many island species. Thus, according to IUCN data, more than 40% of the animal species included in the Red List live on islands.
The loss of biodiversity and the alteration of ecosystems have an unequal incidence depending on the territories, both due to the different degrees of pressure in different areas and due to the variation in resilience against these pressures. Within this global variation, the particular biogeographical conditions of the insular environments determine that these environments currently stand out in terms of biodiversity loss, presenting a problem in terms of conservation of habitats and specific species, which makes a different management necessary.
In turn, fragility depends on both the size of the space and the insulation. The insular phenomenon is very variable, depending on its size, its origin and the distance to the mainland of the insular spaces. These factors determine whether or not there is an initial biological endowment, the degree of possibility of exchange with continental spaces or the possibility of developing complete food chains. All these peculiarities mean that conservation problems are much more virulent in insular spaces.
Among the main problems of the insular spaces, there is the alteration of the habitats, either due to the occupation of the territory by plantations or infrastructures, or due to tourist pressure. In addition, climate change also poses a significant threat to these environments, due to the difficulties of movement of species. However, the main conservation problem faced by island biocenoses is the alterations produced by the introduction of invasive alien species, determined by the great invasibility that characterizes island territories.