Threatened island habitats
Nature
Islands are experiencing increasing demands from growing populations, exacerbating the familiar land degradation problems of the mainland. Islands seem particularly susceptible to species loss. The introduction of species, particularly on remote oceanic islands has caused a tremendous loss of species. Hawaii and the Galapogos islands are prime examples of islands suffering from invasions and introductions.
The demand for commodities and the advent of refrigeration has lead to the establishment of plantations in place of the natural flora. Islands become degraded when they lose their mangroves and coral reefs which protect them from storms and soil erosion. Mining particularly for phosphates has done great damage to islands especially in the west indian ocean and pacific.
Military activity has caused the degradation of many islands, many to the extent that the local populations have had to leave. Bomb damage, construction of air strips, military infrastructure and most poignantly the testing of nuclear and other destructive weapons, has virtually destroyed many islands.
Islands or island groups, which often have high rates of endemicity, face particularly high levels of threat to their flora. Indeed, seven of the top ten areas listed on the IUCN 1997 Red List for plants, according to percentage of threatened flora are islands: St. Helena, Mauritius, Seychelles, Jamaica, French Polynesia, Pitcairn, and Réunion.
Background
Biogeographers recognise two basic types of island; oceanic and continental shelf islands. One view is that, according to size these would differ in species numbers, the ability to 'retain species' and species:area relationships. Larger islands are more likely to have a greater habitat diversity, enabling them to withstand greater pressures on the environment.
Incidence
Easter island was once covered in a now extinct palm species, lost within the last 1000 years. The Madeira islands had extensive tree cover until the Portuguese arrived in the fifteenth century. In the Galapogos, the red quinine [Chinchona auccirubra] is threatening the native flora and fauna over large areas. The list of islands where man (both aboriginal and european colonists) have affected the native flora and fauna is a long one. Introduced reindeer, sheep and rabbits have done great damage to the island tussuck grasses of New Zealand, S. Georgia, Kerguelen island and other islands of the southern oceans and the south Atlantic. Livestock and fuelwood collection has decimated many island forests.
Claim
An understanding of the way in which species are lost from islands is crucial, since in effect conservation areas are all islands in a sea of disturbance/development.
Aggravates
Aggravated by
Strategy(ies)
Value(s)
Type
(D) Detailed problems