Reasons for the weed risk assessment system

All plants imported into Australia, regardless of end use, have the potential to become weeds in Australia. Having a system to screen new plant introductions for weed potential reduces the chances of new weeds entering Australia.

Since the 1800s, new plant species have been introduced into Australia for a range of uses including agricultural production, horticulture and as ornamental plants. Over time a proportion of these species have escaped from domestic or agricultural cultivation and become weeds in Australia.

There are approximately 15,800 native plant species and close to 29,000 introduced exotic species in Australia (Diez et al. 2009). Of these introduced species, about 3,300 species have naturalised (Gallagher et al. 2015) and approximately 500 of these species are now proclaimed as noxious weeds under state/territory legislation (Invasive Plants and Animals Committee 2015).

Garden plant introductions are the primary source of new naturalised plants and weeds in Australia (Groves et al. 2005). Of the 3,300 introduced plant species now estimated to be established in Australia, 70 % are escaped garden plant species (Virtue et al. 2004; Groves et al. 2005). The economic cost of naturalised weed species to Australian agriculture is estimated to be over $4 billion annually (Sinden et al. 2004). The environmental cost is also high, with invasive species second only to land clearing as a cause of global biodiversity loss (DEWHA 2007). Additionally, weeds have non-monetary costs, such as health costs (for example, plants that cause asthma or skin irritations), amenity costs (for example, plants that choke waterways preventing passage) and aesthetic costs.

The direct cost of weed control is largely borne by governments and landowners (Martin 2008). Preventing the importation of potential new weed species may result in the reduction of future weed control expenditure.

Legislative controls

The Department of Agriculture and Water Resources is responsible for developing and implementing biosecurity policies in Australia, in line with Australia's international rights and obligations and Commonwealth Government policies.

Under the Biosecurity Act 2015, the department regulates the importation of all types of plant material through the Biosecurity (Conditionally Non-prohibited Goods) Determination 2021, including propagatable plant material, into Australia.

The Department of the Environment is the agency with administrative responsibility to restrict plant imports under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). During the development of the Weed Risk Assessment system it was determined that it adequately assesses the potential environmental risk of plant imports. The Live Import List established under the EPBC Act is taken to include any plant species allowed to be imported under the Biosecurity Act 2015.

Australia’s international obligations

In developing biosecurity policies for the importation of plants and plant products, the department complies with Australia’s international rights and obligations. These rights and obligations result from Australia being a signatory to both the World Trade Organisation, under the Agreement on the Application of Sanitary and Phytosanitary Measures (the SPS agreement), and the International Plant Protection Convention.


Department of the Environment (2007) Weeds in Australia – Department of the Environment website.

Diez JM, Williams PA, Randal, RP, Sullivan JJ, Hulme PE, Duncan RP (2009) Learning from failures: testing broad taxonomic hypotheses about plant naturalization. Ecology Letters, vol. 12, pp. 1174–1183.

Gallagher RV, Randall, RP, Leishman MR (2015) Trait differences between naturalized and invasive plant species independent of residence time and phylogeny, Conservation Biology, vol. 29, pp. 360–369.

Groves RH, Boden R, Lonsdale WM (2005) Jumping the Garden Fence: Invasive garden plants in Australia and their environmental and agricultural impacts. CSIRO report prepared for WWF–Australia. WWF–Australia, Sydney.

Invasive Plants and Animals Committee (2015) Weeds Australia: Noxious weeds list for Australian states and territories, available at, accessed 23 May 2016.

Martin P (2008) Cross pollination or cross-contamination? Directions for informing the management of invasives with marker-economy concepts. Proceedings of the 16th Australian Weeds Conference, 18–22 May 2008, Cairns Convention Centre 6–13.

Sinden J, Jones R, Hester S, Odom D, Kalisch C, James R, Cacho O (2004) The economic impact of weeds in Australia, CRC for Australian Weed Management, Adelaide, Technical Series No 8, Adelaide. pp 55.

Virtue JG, Bennett SJ, Randall RP (2004) Plant introductions in Australia: How can we resolve "weedy" conflicts of interest? . In 'Weed management: balancing people, planet, profit. 14th Australian Weeds Conference, Wagga Wagga, New South Wales, Australia, 6–9 September 2004: papers and proceedings.' (Eds BM Sindel, SB Johnson.) (Weed Society of NSW: Sydney).​

Last reviewed: 20 March 2021
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