Getting rid of island gatecrashers

21 May 2010 | News story

Climate change can have a devastating impact on islands worldwide but an even greater threat to these often remote and isolated biodiversity ‘hotspots’ comes from its uninvited inhabitants – invasive alien species. Although many of us are unaware of this growing threat, invasive species are the second biggest threat to biodiversity, placing both nature’s and people’s well-being under serious pressure.

Although islands cover only 5% of the Earth’s land surface, they are home to approximately 20% of all known terrestrial species and almost half of all endangered species.

However, this exceptional diversity is also exposed to exceptional dangers. Island ecosystems are particularly fragile and vulnerable due to their size and the fact that they are often isolated. Overharvesting of resources, natural disasters and other major causes of biodiversity loss, such as climate change and invasive species, are one of the main threats to islands, with the latter having a truly devastating impact on its biodiversity.

70–95% of the world’s terrestrial species extinctions have occurred on islands, and most of these (55–67%) were directly caused or facilitated by invasive alien species, introduced through ballast water, hull fouling and aquaculture.

Invasive species are species introduced to a new area where they establish, spread and cause negative impacts on biodiversity, livelihoods or development. For example, Kdzu (Pueraria Montana), which was originally used to combat soil erosion, has now spread out of control, smothering native plants and uprooting trees. It can grow as fast as a foot a day.

Invasive alien species are recognized as one of the major reasons for biodiversity loss worldwide, with significant impact also on other sectors, including economic development, health, agriculture, tourism and trade. The global cost of invasive alien species impacts is estimated at around US $ 1.4 trillion annually.

So what are the best ways of dealing with invasive species?

“One of the key ways is to identify and control them before they become established and overrun native species”, says Geoffrey Howard, Global Invasive Species Coordinator from IUCN’s East and Southern Africa office. ”If there isn’t a rapid response, they can become increasingly difficult to deal with and have a bigger impact on biodiversity.”

A workshop aiming to help island nations find effective ways of managing invasive alien species was organized by the Global Island Partnership and its results were presented at a side event during the fourteenth meeting of the Subsidiary Body on Scientific, Technical and Technological Advice (SBSTTA) in Nairobi.