Photographer : Leigh R. Hilbert
So what are they?
The Australian government defines invasive species as 'a species occurring, as a result of human activities, beyond its accepted normal distribution and which threatens valued environmental, agricultural, or other resources by the damage it causes.' In short, invasive species are animals that have been artificially introduced to their current environment, such as the many species that were introduced into Australia during European settlement. Sometimes these species are intentionally brought somewhere, and other times they hitch a ride on cargo ships or trucks.
Typically, an invasive animal will fill an ecological niche that no animal currently fills, and it will be allowed to flourish. Unfortunately, sometimes the animal flourishes a bit too much, resulting in devastating consequences for the ecosystem.
Close to home
The classic Aussie example is the cane toad, an animal purposefully introduced by the sugar cane industry in 1935 to control the cane beetle population. While the cane beetle problem lessened, the toads grew out of control. With no predators that can control its numbers, the cane toad ran rampant. It will eat any animal it can fit in its mouth, and is a carrier for diseases such as salmonella. The toad has also caused problems because it poisons any of the larger animals that try to eat them. While research is being conducted, there is still no proven method of controlling toads, which are adapting and reproducing at a rapid pace.
Another, lesser-known instance of invasive species is on Macquarie Island, just 1500 km southeast of Tasmania. The World Heritage-listed-island has historically been a natural refuge and breeding ground for many varieties of rare birds, including king penguins and two species of nationally threatened albatross.
Yet this site is becoming increasingly threatened by rabbits and other rodents. Since the 1980s, the rabbit population has increased from 10,000 to more than 100,000, all within an area of 128 sqaure km. All those rabbits need something to eat, and eat they do—so much, in fact, that they’ve totally stripped some hillsides of vegetation. This can be devastating during rainfall; during some months, as many as 20 landslides have occurred, sometimes killing penguins in the process.
What can be done?
There are several ways to deal with invasive species. The Tasmanian government has come up with a $15 million plan to completely eradicate the rodent population on Macquarie Island. After a similar program was successful on Campbell Island in 2001, conservationists are confident that this program would be effective on Macquarie Island as well.
The cane toad, however, is a bit more of a problem. It has become so widespread, stretching from Melbourne to Kakadu National Park, that the only effective removal takes place on the local level. Some people trap the toads, while others are doing research on a virus that would affect only the cane toad and destroy its population.
The NSW Invasive Species Plan for 2008-15 has attempted to help prevent and manage the invasive species issues that the state currently faces by following four steps. The first is to exclude, or to prevent the start of any new invasive species, and the second is to destroy or contain the spread of new invasive species, The third step is to effectively manage, or reduce the impacts of widespread invasice species, and finally, the fourth step is capacity building, or ensuring that NSW has the ability to manage invasive species.
This page was updated by Laura318.
How do I know this?
Australian Government, Department of the Environment, Water, Heritage and the Arts, 'Invasive Species', http://www.environment.gov.au/biodiversity/invasice/index.html, viewed 19 May 2009
Department of the Environment and Heritage 2004, The feral cane toad (Bufo marinus), http://www.deh.gov.au/biodiversity/invasive/publications/cane-toad/index.html
Invasive Species Council, 'Working to stop further incasions', http://www.invasives.org.au/
NSW Department of Primary Industries 'NSW Invasive Species Plan 2008-2015', http://www.dpi.nsw.gov.au/agriculture/pests-weeds/nsw-invasive-species-plan
Wikipedia Free Encyclopaedia, Invasive Species, http://en.wikipedia.org/wiki/Invasive_species
WWF Australia 2006, Grey-headed albatross face extinction on Macquarie Island,http://wwf.org.au/news/grey-headed-albatross-face-extinction-on-macquarie-island
WWF Australia 2006, Precious island 'arks' under attack, http://wwf.org.au/articles/precious-island-arks-under-attack/
WWF Australia 2006, World Heritage island under threat, http://wwf.org.au/news/world-heritage-island-threatened-by-rabbits-and-rats/
