Why pest controls are necessary

Climate change, the environment, land and water management, and conservation of native flora and fauna, are all concerns of early 21st century Australia. However, these issues also matched those of the European settlers who arrived here from 1836, with differing emphasis and priority.

The early settlers faced the task of establishing a new colony in a land that was relatively unknown to them. Even those who were alert to the circumstances and difficulties elsewhere on the Australian continent had to contend with the vagaries and subtle differences of that vast area that was christened South Australia. Read more information concerning the Settlement and Development of South Australia.

Care of our land resources is vital for the economic well-being of South Australia. There is considerable potential for the State to underpin its economic development from primary industries by adopting sustainable land management practices. Conversely, economic development is essential if we are to improve our management of these land resources.

Community interest in land management and resource protection is growing, shown by:

• the increasing number of debates on the future of the arid zone
• a greater interest in land care
• the proper management of water resources, pollution control, and biodiversity
• management of conservation lands, and related issues.

A fundamental component of this is the control of pest animals and weeds. These pests threaten the full potential, sustainability and benefits of:

• agricultural, pastoral, industrial and public enterprises or works
• conservation and biodiversity
• the health and safety of people.

All livestock and plant production industries are at risk from the impacts of pest animals and weeds.

Pest animals

A ‘pest animal’ is usually a vertebrate animal that becomes established and poses a threat to primary industry, the environment or the community. They are also animals that cause more damage than benefits to human valued resources and social wellbeing [1]. Pest animals impact our soils, native plants and animals, and account for annual production losses worth millions of dollars.

In the two centuries since European colonisation, many exotic animals have been introduced to Australia both legally and illegally. In mainland Australia, it is estimated that at least 73 species of introduced vertebrates have established wild populations, including:

• 25 mammal species
• 20 birds
• four reptiles
• one amphibian
• at least 23 freshwater fish.

Some introduced pests — such as rabbits and foxes — are now so widespread in Australia that there is no prospect of eradication. It is no longer technically feasible, as the huge area of the continent is beyond the capacity of the country to fund the initial and potential ongoing costs.

Weeds

At its simplest, a ‘weed’ is any plant growing where it is not wanted. In terms of government and land holder roles it is better described as a plant that requires some form of control action to reduce its negative effects on the economy, the environment, human health and amenity [4].

More than 27,000 exotic plant species have been introduced to Australia since 1788 [5], and at least 2,800 have subsequently naturalised: they establish and spread unassisted unless something is done about them. A 2003 report [6] determined Australia had around 426 major agricultural weeds and about 798 major environmental weeds.

On examining the sources of agricultural, noxious, natural and environmental weeds, it appears that most were deliberately introduced to Australia: only around 7% came accidentally or for reasons unknown [7]. Most food and ornamental plants were planted deliberately; around 70% of weeds have come from gardens, although this only represents around 5% of plants introduced for gardening. Hence, whilst most weeds are originally garden plants, most garden plants do not become weeds.

The need to take action

Concerted action is necessary to eliminate or control a pest, because if left uncontrolled it will have an impact on crops and stock, or even overtake a local eco-system. Yet whatever drastic steps might be taken, new control tool implemented, or preventative procedures adopted to make a situation less likely to recur, there are contradictions and tensions in any method of pest animal or weed control. For example, dingoes are both a protected species in certain areas and a pest that needs to be controlled in others. Feral deer and goats are often sourced from farmed animals. Blackberries can form dense thickets providing cover for both pest and native animals and a food-source for many native birds.

Throughout Australia, many pest animals and weeds are spreading faster than they can be controlled and their management is consuming enormous resources. Climate change poses an additional challenge to our ability to manage these pests.

Some pests will be determined as not cost-effective to be pursuing, others will be pursued at a State level, and some will be national threats. More and faster than ever before, we can use technology for detection and control, although pest animals and weeds are rarely able to be completely eliminated.

For better or worse they can be managed and controlled, but the consequences of these measures still need to be considered carefully. Therefore, science, economics and politics need to coalesce in reaching a decision about striking the optimum balance. Risk assessment is used to determine the pest potential of new animal and plant introductions to Australia.

Legislation

Agriculture was of critical importance to the prosperity of the colony and Government intervention in its development and protection was necessary soon after settlement, to ensure it would continue to expand and flourish. In this regard, pest animals and weeds became matters of public concern, and arrangements to deal with them varied as they assumed greater or lesser importance.

Later, declining biodiversity and the extent and pace of development led to a reassessment of values and ideas, resulting in changes in attitude and behaviour to pests in the natural environment. Effective control of pest animals and weeds by all landowners was considered to be the key to reducing their impacts and fundamental to sustainable land management as well as environmental and community values.

Legislation was passed to deal with pest animals and weeds, although not all of these were legally defined as such at the time. For example, the Crown Lands Consolidation Act 1886 provided for the erection of rabbit-proof and vermin fences (see list of South Australian Acts relating to the control of pest animals and weeds from 1839 to 2019).

South Australia has been a leader in passing legislation for the control of pest animals and weeds. The Scotch Thistle Act 1851 was the first weed control legislation in Australia. The Rabbit Destruction Act 1875 was the first rabbit control legislation in Australia. As far as we can ascertain, both were the first such legislation in the world.

The Dogs Act 1852, the first of a series that confronted the nuisance caused by uncontrolled domestic and native dogs, was a precursor to what eventually became the Dog Fence Act 1946. But such statutes were, in a sense, negative, in that they were designed to prevent certain things from happening rather than taking direct steps to improve conditions positively.

Between 1839 and 2019 there have been 141 Principal or Amendment Acts in South Australia relating to the control of pest animals and weeds. This includes Acts targeting individual species through to a single scheme that integrated pest animal and weed control. Acts to control certain individual species were introduced, such as for thistles, dogs, horses, camels and sparrows, but these species were soon merged with others into more general Acts as the number of pest species grew.

Paradoxically, between the 1860s and the 1950s there were Acts that prevented the destruction of what were to become introduced pest animals, such as pheasants, sparrows, deer, rabbits, blackbirds and starlings. These were Acts for the protection of animals (and later birds) and for game. In total, there were 20 Principal or Amendment Acts for these purposes.

To administer this legislation, responsibility for implementation was vested first with the central Government, then later with local councils and finally with dedicated local boards (for details see the chronological period histories relating to the control of pest animals and weeds).