Biosecurity legislation, dispersal of local weeds and the tort of private nuisance

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Philip Blackmore

New South Wales Department of Primary Industries, PO Box U86, University of New England, New South Wales 2351, Australia.

Cite this article as:

Blackmore, P. (2013) Biosecurity legislation, dispersal of local weeds and the tort of private nuisance. Plant Protection Quarterly 28(3), 83-84.


Following the Australian Government, many Australian states are considering replacing a raft of biosecurity laws with a single biosecurity statute: for example Queensland is much more advanced in this process than New South Wales. Biosecurity law is generic by nature and relies on a number of all encompassing definitions. Biosecurity law can also apply to noxious weeds but would be limited to species that pose a significant threat to the economy, environment and/or community. This type of law aims to prevent or limit the impacts of external costs created by the spread of weeds (or other pests or disease) to new areas. It is inefficient when used to limit the dispersal of established local weeds. Civil tort law, however, may offer a remedy to landholders harmed by ongoing and uncontrolled dispersion of such local weeds.

Keywords: general biosecurity obligation, biosecurity matter, biosecurity event, external cost.


The Beale Review on National Biosecurity Arrangements (2008) recommended the consolidation of biosecurity functions into a single organisation which would operate under a single statute. The Australian Government is leading the way with a bill to replace the Quarantine Act 1908 currently before the Senate. Some of the states are also following this lead. The Queensland government has drafted the Biosecurity Bill 2011 for the previous State parliament and the New South Wales (NSW) and Victorian governments are discussing proposals closely based on the Queensland bill at departmental levels.

Biosecurity definitions

The Queensland Biosecurity Bill 2011 attempts to create general statutory arrangements for the management of all biosecurity eventualities. To do this, it creates generic definitions applicable to biosecurity management, viz:

Biosecurity considerations

The triple bottom line, that is, the economy, environment and community with the 

economy including industry, production, market access, tourism, employment and transport;

environment including natural ecosystems, native flora and fauna, and biodiversity; and

community including lifestyle, community infrastructure, social cohesion, human health and well-being, and cultural values.

Biosecurity entity

A person or business who keeps, or premises where a thing is kept, more than a threshold number of designated animals, plants or other biosecurity matter.

Biosecurity event

Something that has happened, may happen, or is happening, that was caused, or that may be or may have been caused, by biosecurity matter which has had, is having, or may have a significant adverse affect on a biosecurity consideration.

Biosecurity risk

The risk of an adverse effect on a biosecurity consideration caused by, or likely to be caused by, biosecurity matter, dealing with biosecurity matter or a carrier, or carrying out an activity relating to biosecurity matter or a carrier.

Biosecurity matter 

an animal, plant or living thing, other than a human, or part of a human;

a disease, including a prion; and/or

a contaminant.

General biosecurity obligation

The Queensland bill also creates a duty which applies to all persons dealing with, or carrying, or carrying out an activity with biosecurity matter.

A person has an obligation to:

take all reasonable and practical measures to prevent or minimise the biosecurity risk;

prevent or minimise adverse effects on a biosecurity consideration when dealing with the biosecurity matter, or carrier, or carrying out the activity;

minimise the likelihood of causing a biosecurity event, and limit the consequences of a biosecurity event caused by dealing with the biosecurity matter, or carrier, or carrying out the activity; and/or

not do, or omit to do, something if the person knows, or ought reasonably to know, that doing, or omitting to do, the thing may exacerbate adverse, or potentially adverse effects of the biosecurity matter, carrier or activity on a biosecurity consideration.

The provisions of the bill apply to declared biosecurity matter but many of the provisions, including the general biosecurity obligation, also apply to un-declared matter if this matter could create a biosecurity event. Several of the management tools proposed by the bill can be applied to both declared and undeclared biosecurity matter. Under the bill many existing noxious weeds could be declared as biosecurity matter but local noxious weeds (New South Wales Class 4 equivalent) are excluded by the requirement that declared biosecurity matter must have a significant impact on a biosecurity consideration. In Queensland, this exclusion has no consequence as local government in that state has the power to declare local weeds under the Queensland Local Government Act 2009. It is unlikely that local government in New South Wales would gain an equivalent power.

Why are weeds declared?

Weed spread and ongoing dispersal of established weeds create harm to the economy, environment and the community (Blackmore 2008). Various methods can be used to try to prevent this harm, or to provide a remedy to individuals who have suffered harm from this cause.

The problem of weed spread

Spread of a weed species is the occupation of new areas (Auld et al. 1978/9, Forcella, 1985). Weed spread creates external costs (Menz and Auld 1977, Pannell 1994, Jones 2000). External costs occur when the actions of individuals impose unintended impacts on others. Pannell (1994) describes several approaches to abating the impact of external costs, these being:

the market;

a Pigovian tax; and


The market

The use of the market as a method of managing external costs and its associated problems, is discussed in Blackmore (2005). The market is not an effective method as externalities are a form of market failure (Pannell 1994).

A Pigovian tax

This is a tax which aims to internalise external costs to the entities which create those costs (Pannell 1994). It is commonly referred to as the “polluter pays principle”. The Australian governments’ carbon tax is a Pigovian tax. This approach is most suitable where the external cost is constant such as pollution from factories (Baumol 1972).


Regulation is the standard government approach to prevent or limit the creation of external costs caused by weed spread (Burns 1974, Menz and Auld 1977, Pannell 1994, Jones 2000). This has been the case in New South Wales for more than 100 years (currently the Noxious Weeds Act 1993) and more than 150 years in Victoria. Regulation is most effective when applied to weed incursions into new areas and to emerging weed populations (Hobbs and Humphries 1995). When used to limit the dispersal of widespread weeds, regulation can be anti-competitive and inefficient (Carter 2000), except where the majority of the community support compulsory control of a widespread local weed.

Civil tort law – A possible alternative to regulation 

In situations where landholders are being harmed by the ongoing dispersal of established weeds (local weeds) civil tort law might create an opportunity for the landholders themselves, rather than government, to take responsibility for regulating the impact of those weeds. This could be achieved by seeking to apply the law of private nuisance to landholders who cause harm to others by failing to limit the dispersal of local weeds. Preston CJ in Robson v Leischke at para 42 defined private nuisance as

an excessive act or omission which is an unreasonable interference with, disturbance of, or annoyance to a person in the exercise or enjoyment of his or her ownership or occupation of land or some profit or right used in connection of the land.”

The tort of private nuisance and its application to the spread of things naturally on the land is discussed in Blackmore (2011). French v Auckland City Corporation is the landmark private nuisance case in relation to weed spread (Burns 1974). This New Zealand case was about the dispersal of variegated thistle (Silybum marianum) seed and other weeds from land owned by the City to land occupied by the plaintiff. French had made considerable efforts to control weeds including variegated thistles on his land but the City’s attempts at weed control were cursory. French was successful in his action, even though variegated thistle continued to be widespread on his land and was not a noxious weed in the district.

A nineteenth century British case, Proprietors of Margate Pier and Harbour v Town Council of Margate, a case involving the responsibility for removal of an accumulation of rotting seaweed in Margate harbour, subject to the Nuisances Removal Act for England 1855, may also have relevance to weed spread. It could be argued that unrestrained weed spread would be in breach of the general biosecurity obligation. A landholder could be liable in nuisance where the landholder failed to prevent ongoing dispersal of a locally widespread weed. The dispersal would need to be by natural means, that is wind, water or wild or feral animals, rather than by some negligent act, c.f. French v Auckland City Corporation. However the degree of harm must be significant. Harrison J in Hill v Higgins at para 49 stated that

to be liable in nuisance, the annoyance or discomfort must be substantial and unreasonable”.

Burns (1974) reported that the test for nuisance caused by nature was established in Goldman v Hargrave, an action brought both in nuisance and negligence. The Privy Council regarded three factors to be of critical significance in relation to the existence of a duty of care by the occupier, these being:

knowledge of the hazard;

ability to foresee the consequences of not checking or removing it; and

the ability to abate the hazard.

However the Privy Council qualified the duty of an individual to the extent that “what it is reasonable to expect of him in the circumstances” in both a physical and financial sense (Burns 1974, Gardner 1998). A reciprocal duty was also imposed on neighbours to take similar reasonable steps to protect their own interests.


Biosecurity legislation may leave landholders without protection from the externality caused by the unconstrained dispersal of local weeds. Civil tort law may provide a remedy to this problem even though it is reactive by nature: a claim for damages can only be brought for harm that has already occurred, not for potential harm. However, should a significant private nuisance action for weed spread be successful, the threat of costly litigation may be enough to encourage errant landholders to improve their weed management practices. The tort of private nuisance may therefore prove to be an effective tool for landholders to seek a remedy to harm caused by unchecked local weed dispersion.


Auld, B.A., Menz, K.M. and Monaghan, N.M. (1978/79). Dynamics of weed spread: implications for policies of public control. Protection Ecology 1, 141-8.

Baumol, W.J. (1972). On taxation and the control of externalities. American Economic Review 62(3), 307-22.

Blackmore, P.J. (2005). Why declare? The role of government in weed management. Proceedings of the 13th NSW Biennial Weeds Conference. (New South Wales Department of Primary Industries, Orange, Australia).

Blackmore, P. (2008). Noxious weeds or just obnoxious? (accessed 15 May 2013).

Blackmore, P.J. (2011). Can the common law of nuisance effectively manage weed spread? Proceedings of the 16th New South Wales Weeds Conference. (Weed Society of New South Wales, Wahroonga, Australia).

Burns, P. (1974). Liability for blowing thistle down and seed: a thorny problem resolved. The Modern Law Review 37, 702-5.

Carter, R.J. (2000). Principles of regional weed management and quarantine. In ‘Australian Weed Management Systems’, ed. B.M. Sindel, pp. 83-104. (R.G. and F.J. Richardson, Melbourne). 

Forcella, F. (1985). Final distribution is related to the rate of spread in alien weeds. Weeds Research 25, 181-91.

Gardner, A. (1998). The duty of care for sustainable land management. The Australasian Journal of Natural Resources Law and Policy 5(1), 29-63.

Hobbs, R.J. and Humphries, S.E. (1995). An integrated approach to the ecology and management of plant invasions. Conservation Biology 9(4), 761-70.

Jones, R.E. (2000). The economics of weed control. In ‘Australian Weed Management Systems’, ed. B.M. Sindel, pp. 267-83. (R.G. and F.J. Richardson, Melbourne).

Menz, K.M. and Auld, B.A. (1977). Galvanised burr, control and public policy towards weeds. Search 8, 281-7.

Pannell, D.J. (1994). Economic justifications for government involvement in weed management: a catalogue of market failures. Plant Protection Quarterly 9(4), 131-7.


French v Auckland City Corporation [1974] 1 NZLR 340

Hill v Higgins [2012] NSWSC 270

Goldman v Hargrave [1967] 1 AC 645

Proprietors of Margate Pier and Harbour v Town Council of Margate (1869) 20 L.T. (N.S.) 564

Robson v Leischke [2008] NSWLEC 152

First published online: September 6, 2013