Introduction of exotic species
It is estimated that Australia gains around 20 new pests or diseases each year. Some well-known examples include cane toads, rabbits, willows and, more recently, black striped mussels and red fire ants.
Historically, feral cats, foxes and rabbits have been a cause of local extinctions and significant reductions in range for native species through a combination of habitat modification and predation. They are a major ongoing problem.
Weeds are an equally significant pressure on ecosystems, with more than 2,500 species of introduced plants now thriving in the wild in Australia. They have invaded every part of the landscape - bushland, rangelands, coasts, rainforests, deserts and farms.
Ballast water from shipping has been responsible for introducing more than 250 species, and possibly as many as 500 species, into Australian waters.