Weeds are among the most serious threats to Australia's natural environment and primary production industries. They displace native species, contribute significantly to land degradation, and reduce farm and forest productivity.
Invasive species, including weeds, animal pests and diseases, represent the biggest threat to our biodiversity after habitat loss. Weed invasions change the natural diversity and balance of ecological communities. These changes threaten the survival of many plants and animals as the weeds compete with native plants for space, nutrients and sunlight.
Throughout Australia, weeds are spreading faster than they can be controlled. All Australian states and territories have experienced native plant invasions. Nationally the impact of invasive plants continues to increase with exotic species accounting for about 15% of all flora. This figure is increasing by about 10 species per year.
Weeds typically produce large numbers of seeds, assisting their spread, and rapidly invade disturbed sites. Seeds spread into natural and disturbed environments, via wind, waterways, people, vehicles, machinery, birds and other animals.
Human activities and introduced animals, such as rabbits, cattle, horses, goats and pigs, can create good conditions for weed growth and contribute to weed spread. Weeds can contribute to soil disturbance, loss of native plant cover, and changed burning patterns. They also thrive where fertilizers and other wastes are washed into bushland, leaving extra nutrients in the soil.