Weeds are one of the most serious threats to Australia's environment and primary production resource base. Nationally pest plants continue to invade the land with exotic species accounting for about 15 per cent of flora. About one-quarter of them are either serious agricultural and environmental weeds or have the potential to be serious weeds. Almost all of Australia's native vegetation has been, or could be, affected by weeds. Those affects could include changes to the structure, species composition, fire frequency and abundance of native ecosystems.
Weeds reduce farm and forest productivity, displace native species and contribute to land degradation. The cost of weeds to agricultural industries is estimated at about $4 billion a year. The cost of weeds to the environment is difficult to calculate but could be greater than the estimated cost to agricultural industries.
To combat weeds the Australian Government and all state and territory governments developed the Australian Weeds Strategy. Under the strategy, 32 of Australia's most significant weed species are listed as Weeds of National Significance. After over a decade of national coordination all of these have returned to state and territory management.