Invasive plants and animals

Invasive species are plants or animals that do not belong where humans have intentionally or accidentally brought them.

Why some species are unwelcome


Hundreds of extinctions have been caused by invasive alien species. The ecological cost is the irretrievable loss of native species and ecosystems.

IUCN, the International Union for Conservation of Nature, states that the impacts of invasive species are immense, insidious and usually irreversible. They may be as damaging to native species and ecosystems on a global scale as the loss and degradation of habitats.

For example, European red foxes introduced into Australia have taken a toll on many native species, including small and medium-sized rodents and marsupials.

Growing global trade and communication is directly contributing to the mixing of wildlife across bio-geographical boundaries.


Growing realisation of the ecological costs of invasion


Some species that appear in new environments die, while others thrive and become invasive. In many cases, native species are likely to be unprepared to defend themselves against the invaders. This process, together with habitat destruction, has been a major cause of native species extinction throughout the world in the past few hundred years.

In the past, many of these losses have gone unrecorded. Today, there is a growing realisation of the ecological costs of biological invasion in terms of the native biodiversity losses.


Countering the invaders


Biologists are investigating how these invaders succeed in establishing themselves in new environments so that, where necessary, the intruders can be controlled and eradicated.

Click here to read more about Rats and Cats.
Invasives Redhot pokers  / ©: Averil Bones / WWF-Aus
Invasives Redhot pokers
© Averil Bones / WWF-Aus

Garden Escapees & Cane toads

The cane toad is one of the world's 100 worst pest species, according to the World Conservation Union.

Go to our Cane Toad page (archived)

Escaped invasive garden plants are the biggest source of agricultural and environmental weeds, costing farmers many millions of dollars each year.

Go to our Garden escapees page (archived)