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).
The chemicals that are needed to control weed infestations can mean added pressures on ecosystems.* (Information courtesy of “Paying the Prince of Garden Escapes” by the Australian Association of Bush Regenerators, NSW Inc.)
Weeds cost the farming sector $4 billion a year but their impact on biodiversity is incalculable.
An alarming inter-relationship that makes it even more urgent to control weeds, is that between weeds and climate change.
The impacts of weeds are vast and serious. The need to control this problem is urgent and it requires the effort of everyone.