Weeds have significant economic, environmental and social impacts.
Weeds have the potential to adversely alter ecosystem function, reduce primary industry productivity and profitability, and seriously limit the long-term sustainability of all the state's agricultural and natural resources.
They increase the risk of fire, increase costs to infrastructure maintenance, and reduce the amenity of recreation areas. Some weeds have well-documented and sometimes serious effects on human health.
Weeds cost Queensland an estimated $600 million every year.
The negative economic impacts of weeds include:
- competition with pastures leading to reduced stocking capacity and erosion
- toxicity to stock
- competition with crops for water and nutrients
- increased stock mustering costs
- loss of ecotourism values
- impacts (of aquatic weeds) on water quality and irrigation
- management costs arising from the use of physical, mechanical and chemical control methods.
Just 5 weeds - parthenium weed (Parthenium hysterophorus), rubber vine (Cryptostegia grandiflora), prickly acacia (Acacia nilotica), mesquite (Prosopis spp.) and parkinsonia (Parkinsonia aculeata) - cost Queensland more than $50 million each year in lost production and costs of control.
The cost of reduced production in the Mulga lands of South West Queensland, caused by the intrusion of woody weeds and the ensuing erosion, is estimated at over $50 million each year.
The estimated annual cost of weeds in winter crops in southern Queensland alone is $40 million.
Weeds can degrade natural vegetation and impact on biodiversity generally.
Rubber vine has the potential to completely destroy all deciduous vine thickets in northern Queensland, which would lead to the loss of entire unique ecosystems and the extinction of many plant and animal species.
Cat's claw creeper (Macfadyena unguis-cati) and bitou bush (Chrysanthemoides monilifera ssp. rotundata) also have serious environmental impacts.
Weed management practices may also have environmental impacts. Tillage can result in soil erosion and subsequent pollution of river systems. Inappropriate use of fire in weed management programs may result in ecosystem modification.
Social impacts include effects on human health, recreation, safety and aesthetics.
Parthenium weed has a significant impact on human health in heavily infested central highlands areas of Queensland. People can suffer serious allergic reactions, such as dermatitis and rhinitis or asthma, on contact with the plant or its pollen.
Many aquatic weeds, such as salvinia (Salvinia molesta), cause safety hazards. Small children have drowned when they thought the floating carpet of salvinia was solid ground. Aquatic weeds also interfere with recreational activities (such as swimming and canoeing), and reduce the aesthetic value of lakes and streams.
Weed control is an essential component of road and railway corridor maintenance, especially with regard to safety considerations.