Weeds are a major threat to the natural environment, having an impact on biodiversity and ecosystem function as well as soil and water quality.
Many weeds were introduced by European settlers and have since spread beyond the towns and settlements. Weeds can invade vast areas of grazing land, making it less productive. They can also harm stock and native animals if they carry burrs or prickly spikes and spines. Some may be poisonous if eaten.
Weeds compete with native plants for space, nutrients and sunlight, and can choke waterways and woodlands.
Land clearing or overgrazing can reduce native vegetation, making it easier for weeds to grow and spread in areas. At the same time, this can reduce the ability of native vegetation to compete with and suppress invading weeds. Drought, floods, cyclones and sometimes even fire, can also provide conditions for weeds to flourish. Weeds can be spread by wildlife, stock or via waterways and even wind.
There are a number of declared ‘Weeds of National Significance (WoNS)’ that have been defined by the government as key to control. Landowners and land managers at all levels are responsible for managing WoNS. State and territory governments are responsible for legislation, regulation and administration of weeds. Those relevant to the rangelands of WA of:
- Parkinsonia (Parkinsonia aculeate)
- Mesquite (Prosopis spp.)
- Rubber vine (Cryptostegia grandiflora)
- Prickly Pears (Opuntia spp.)
- Mimosa (Mimosa pigra)
- Prickly Acacia (Vachellia nilotica)
- Gamba Grass (Andropogon gayanus)
Weeds can be controlled by a variety of methods including physical control (removal by hand, cutting, burning), chemical control and biological control (using insects, grazing animals or disease).
Key to the management of weeds is collaboration between land managers. Weeds do not care if there are property borders–they will spread across whole catchments, making coordinated management the best way to locate, eradicate, and control them in the long term.
De Grey LCDC, Factsheet 3 – Parkinsonia Control