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Boiga irregularis /Brown tree snake [Gordon Rodda]
Osteopilus septentrionalis/Cuban tree frog [Cary Bass]
Rattus norvegicus/Brown rat [US National Park Service]
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Invasive Species



What are they?


How do they spread?


What are their impacts?


Managing their spread



About Invasive Species

Invasives: A Major Conservation Threat

A flurry of recent aticles call upon the conservation community to embrace invasive species. Davis and coauthors propose downsizing the struggle against invasives (1). In the News Focus story “Embracing invasives” (18 March, p. 1383), G. Vince suggests that the Galápagos “embrace the aliens.” In The New York Times (2), H. Raffles accused environmentalists, conservationists, and gardeners targeting invasive species of being unreasoningly dogmatic and xenophobic.

These articles imply that the concern with invasive species derives from the unreasonable desire to maintain pristine ecosystems and exclude all alien species. In fact, conservationists recognize that species distributions are constantly changing, that community structure is dynamic, that alien species enter and are introduced into natural communities, and that modifi ed (and even degraded) ecosystems have conservation value...

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22 July 2011

We need to strengthen, not weaken, the struggle against harmful invasive species

An ISSG response to recent articles calling us to re-think the struggle against biological invasions

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15 June 2011

The Invasive Species Problem

The homogenization of biodiversity through the intentional and unintentional introduction of invasive species is accelerating. Increased global trade, transport and tourism, has expanded the movements of organisms from one part of the world to another through newly created pathways.

Many species introduced into new environments are unable to survive in their new surroundings. However, a percentage of these species are able to expand the area they infest and negatively impact the economy, human health or ecology of a region and are termed invasive. Habitat alteration and invasive species impacts have been the major cause of species extinctions over the past few hundred years, increasing the rate of extinction by about 1,000 percent. Although in the past, many of these losses have gone unrecorded, today, there is an increasing realization of the ecological costs of biological invasion in terms of irretrievable loss of native biodiversity and degradation of ecosystem functioning. While the underlying causes of invasive species threats are significant and global in nature, these threats can be effectively dealt with through collaborative efforts at regional and local levels, especially through prevention, early detection and rapid response.

Biologists are trying to characterize a species capability to invade in the hope that incipient invaders can be predicted and stopped. Factors may include: an organism has been relieved of the pressures of predators or parasites of its native country; being biologically "hardy", for example, has short generations and a generalist diet; has many dispersal mechanisms (wind, water, animals, humans); arriving in an ecosystem already disturbed by humans or a natural event. But whatever the causes, the consequences of such invasions - including alteration of habitat and disruption of natural ecosystem processes - are often catastrophic for native species.

A major challenge of our time is to understand the influence of climate change on the complex interactions and impacts of invasive species on natural and human-altered ecosystems.



The list of '100 of the World's Worst Invasive Alien Species' illustrates the incredible variety of species that have the ability, not just to travel in ingenious ways, but also to establish, thrive and dominate in new places. Today, alien invasion is second only to habitat loss as a cause of species endangerment and extinction.

View 100 of the  World's Worst Invasive Alien Species

Click here to view images and follow links to species profiles of '100 of the World's Worst Invasive Alien Species' on the Global Invasive Species Database.