One third of the Australian continent, Western Australia is one of the most unique and biodiverse regions on the face of the planet. Of the state’s 12,000 plants, more than half are found nowhere else, a situation shared by many of our marsupial and marine species.
Invasive or exotic species are capable of doing immense harm to the state’s environment, agriculture and quality of life. However, preventing the entry of such species, together with controlling species already present, is not well co-ordinated, with no state-wide body able to advise government on invasive species issues. For example, the cane toad is knocking on WA’s northern border and it took a concerted effort by the voluntary conservation movement to achieve some positive action by the state government.
We must get serious about the dangers posed by invasive species, both to the environment and to the economy. If we allow invasive species to gain a foothold or expand their current populations, we jeopardise not only the intrinsic value of our natural ecosystems but we also place at risk the wide range of benefits we derive from tourism, including ecotourism, agriculture, science and medical research, and the ecosystem services that the natural environment provides (clean air and water, for example), education and bio-prospecting.
Invasive species and their impact
Animal, insect and plant pests are costing Australian landowners and governments more than $6 billion a year in crop and stock losses. About 20 new pests, weeds and diseases take hold in Australia every year, destroying native flora and fauna as well as killing stock.
The fox is the major predator of mid size and weight range marsupials. It is responsible for eating almost to extinction native marsupials, such as the numbat and woylie, and causes annual damage of at least $250 million to Australian agriculture. The fox was introduced from England in 1858 for hunting and is now found everywhere in Australia.
Introduced from England in the early 1800s, the blackberry requires almost $50 million in annual control costs. The range of the plant is about 8.8 million hectares, spread largely through the cooler, wetter areas of Australia, including the southwest of WA.
Released in Victoria in the 1850s, this European bird is a major pest of cultivated soft fruits and cereals, also destroying food crops by defecating on them. In urban areas, the starling nests in houses and tree holes. Evidence from established wine growing areas indicates that 10 to 15 per cent of crop production is commonly lost due to damage caused by starlings.
The rainbow lorikeet is alien to the southwest of WA and numbers have now reached at least 10,000 in metropolitan Perth. Complaints increasingly come from people living in urban areas, as well as from commercial fruit growers about the loss and damage caused to their crops. The lorikeet is a noisy bird that out-competes more timid birds for nest hollows and may displace the western rosella from its only habitat in the world, the south west of WA. The lorikeet has been declared a pest species within the Perth metropolitan area, with an open season declared on the species throughout the southwest division of the state.
The South American fire ant solenopsis invicta has been found in Brisbane and is subject to a $140 million eradication program funded by state and federal governments. The fire ant is a serious threat to agriculture, where its nesting mounds have been shown to damage machinery in cropping areas. The ants eat seeds such as sunflower and canola, reducing crop productivity, while poultry stung by the ant has a lower meat quality. The sting of a fire ant is painful to humans, with small blisters forming up to two days after being stung. Fire ants can invade homes, posing risks to pets and to people confined to bed, while also affecting electrical wiring by chewing through insulation.
The public often has difficulty in recognising some invasive species and distinguishing them from native species. In a state as large as Western Australia, government employees responsible for invasive species identification and control face a difficult task, so the active support of the community in identifying and reporting suspect invasive species must remain a key plank in any government’s environmental and agricultural policies.
To determine the best management options for invasive species, it is necessary to assess their abundance and the existing or potential damage that an individual invasive species may cause. For an analysis of the economic benefits of control, data will be needed on the relationship between control costs, damage levels and net returns, preferably for a range of control options.
While many techniques exist to control invasive species, the actual methods used must at all times be humane and ethical. Regardless of the damage that invasive species may cause to our environment, and in spite of animals, such as foxes and feral cats painfully killing native birds and animals, our control actions must always be undertaken with minimal or no pain inflicted upon the target invasive species.