ISLANDS AND INVASIVES
What is an invasive alien species?
An invasive alien species is defined by IUCN as:
"A species which becomes established in natural or semi-natural ecosystems or habitat, is an agent of change, and threatens native biological diversity."
Invasive alien species come in all shapes and sizes; from mice to mosses to malaria. They are the second biggest threat to global biodiversity after habitat destruction. On some islands invasive alien species are the main threat to native biodiversity - and to peoples livelihoods. Expanding transport networks and increasing trade and tourism mean that few islands are now safe from deliberate or accidental introductions.
For further information on invasive alien species, please click on the following links;
Why focus on islands?
- Islands are important ecosystems
Many island ecosystems are unique. They contain landforms and biotic communities (including aquatic and marine systems) that are not found at continental (land-locked) sites. They also contain a disproportionately large percentage of endemic species (those that occur nowhere else). Islands also provide critical breeding habitats for mobile species such as seabirds and turtles.
Island biotas are especially vulnerable to human-induced changes. More species have gone extinct on islands than in comparable continental sites. For example:
(i) 80-90% of all reptile extinctions
(ii) 80-93% of all bird extinctions
(iii) 50-81% of all mammal extinctions
have taken place on islands
Invasive alien species impacts are escalating rapidly as more alien species become established in island ecosystems. There is a pressing need to more effectively manage the threats invaders pose to islands if further extinctions are to be averted and the livelihoods and lifestyles of island people are to be sustained. Active management - including preventing invasions in the first place, eradicating invasives where this is achievable, or controlling them where other approaches are not feasible is urgently required.
- Islands present important management opportunities
Islands present unique opportunities to effectively manage invasives. As they are isolated by water it is difficult for terrestrial invaders to colonise (or re-colonise) them. Also, because of their isolation and their relatively small size, eradicating some invasive species from islands is potentially more achievable than at continental sites. These attributes, coupled with their vulnerability, make islands important places to "take a stand" against invasives. Exciting recent advances have been made in managing a growing array of invasive alien species on islands, and important social and economic - as well as biodiversity conservation outcomes have been attributed to these successes.
The thrust of the Cooperative Islands Initiative is to build on these successes so that the tide of invasions may be turned back on many more islands around the world.
Last updated 21 May 2008
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