Weeds have devastating impacts on the health of humans, animals and entire ecosystems.
They can cause asthma, hay fever, dermatitis, conjunctivitis and photo (light) sensitivity. Their spines can enter the skin of animals and humans resulting in severe physical injury.
They can smother natural vegetation and out-compete native plants for space, light and water. They can alter fire regimes, nutrient cycling, fauna diversity and hydrology.
Aquatic weeds can cover the entire surface of a water body. In breading down and decaying the dissolved oxygen of the waterbody is consumed, and there is then less upon which the other aquatic organisms depended for life. The waterbody becomes anaerobic. The water body can ‘die’.
A report on the “Impact of Weeds on Threatened Biodiversity in New South Wales” found that weeds threaten 341 NSW plant and animal species, ‘already declared as vulnerable or threatened species under NSW legislation’ and that of the 127 weed species that directly threaten NSW biodiversity, 82 (65 per cent) were introduced to Australia for cultivation as garden plants and 56 (44 per cent) are still available for sale in Australia. (Coutts-Smith and Downey 2006).
