A number of background papers are available, describing different aspects of Weeds of National Significance. These are listed below and may be downloaded using Adobe Acrobat Reader.

Media release (PDF file - 53 kb)
General fact sheet providing background information (PDF file - 27 kb)
Fact sheet describing weed impacts (PDF file - 42 kb)
Fact sheet showing current and potential distribution maps (PDF file - 1.2 mb)
Guidelines for Developing Weed Strategies (PDF file - 67 kb)

The documents are in 'PDF' format and require Adobe Acrobat Reader. If you do not have Adobe Acrobat Reader, click here to download now.

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The Process for Determining Weeds of National Significance

Over the past decade there has been a developing awareness of Australia's weed threat which achieved formal recognition with the launch of the National Weeds Strategy in mid 1997.

A central component of the strategy is the identification of Weeds of National Significance and the resultant coordinated actions across all States and Territories.

The development of an assessment process, nomination of candidate species, assessment and resultant ranking of species, through to final endorsement by Ministerial Councils has no precedent and took two years to complete.

The process developed is based on scientific principles, limited by the availability of national datasets, the ability for adequately quantifying impacts on biodiversity and conservation and the need to gain approval for the process and species by ARMCANZ, ANZECC and Forestry Ministers.

The agreed methodology for determining Weeds of National Significance comprised of the following four major criteria:

• Invasiveness
• Impacts
• Potential for Spread
• Socioeconomic and Environmental Values.

Analytical techniques were required that would enable a ranking that discriminated between species, where, often, only very small differences existed.

Nominations

The weed species nominated by the State and Territories to be assessed against the criteria for Weeds of National Significance represent, in their opinions, the most serious weed problems in Australia.

State and Territory agencies nominated 74 weeds to be tested. By combining similar weed species and eliminating herbicide resistant weeds (as analysis could not be undertaken for some of the criteria on multiple weed species), the number tested was reduced to 71.

The nomination process also provides for assessment of additional species as WONS and the Ministerial Councils agreed on the following:

• Ministers from States and Territories are required to gain agreement from NRMMC for the assessment and the proponent jurisdiction is to fund the assessment and strategy development which is to be managed by the AWC and conducted by independent experts.
• Reconsideration of species already assessed will only by considered where substantial new information is shown to exist.
• Any additional species nominations will require the unanimous endorsement of all relevant States, Territories and Australian Government Ministers to be approved as a WONS weed.

Data Analysis

The National Weeds Strategy Executive Committee (NWSEC) assembled the data, by providing member States with guidelines and formats for data collection, receiving data, verification and standardisation, follow up and on forwarding to the Bureau of Resource Sciences (BRS).

The BRS undertook an objective analysis of the data on behalf of the NWSEC.

BRS used a range of statistical analyses on the various sources of data that comprised the Weeds of National Significance criteria and the NWSEC examined a number of alternative models for ranking Weeds of National Significance.

Five main data sources were used for the Weeds of National Significance analysis:

• an invasiveness and impacts questionnaire was submitted to three expert panels covering weeds for temperate, sub-tropical and tropical environments;
• observed distribution and density for each weed provided by State and Territory agencies and sourced from the literature. This data and published literature was used to predict potential distribution of weeds using climatic modelling;
• economic information on the cost of control for agricultural and forestry weeds provided by State and Territory agencies;
• environmental information on the number of threatened species, communities and IBRA regions provided by State and Territory agencies and the monoculture potential of a weed from the expert panels;
• a qualitative assessment by the expert panels of social impacts caused by a weed (not examined by other data sources).

To allow a comparison of each of the criteria and to facilitate a combination of the criteria and variables within criteria, the majority of data was rescaled. The NWSEC undertook an extensive analysis of the data to investigate the impact of numerous weighting schemes as they affected the ranking of the weeds.

The diagram below summarises the relationship of the criteria and variables used to calculate the weed scores.

Diagram Illustrating the Relationship of all Variables Used in Determining Weeds Of National Significance

Discussion

The lack of appropriate national datasets, number of species assessed, variability of some of the data resulting from different methods of recording made the analysis more difficult. This necessitated that substantial verification and standardisation be applied to the data. Despite these difficulties, the datasets are considered credible, being the best data available on which to make the Weeds of National Significance decision.

The methodology undertaken is not a scientific process, but an attempt to draw together meaningful indicators (where few national datasets exist) and combine them into a form that provides an objective, transparent and defensible ranking system for weeds.

The relativity of the scores for individual species among a group of species is more important than the definitive scores for ranking purposes, therefore Weeds of National Significance are presented in alphabetical order, as any ranking system would be misleading.

Conclusion

It is obvious that the data and information collected has occurred under time and resource constraints which will have impacted to some degree on the analysis. The NWSEC also recognises that the Weeds of National Significance list and overall ranking will generate considerable discussion. However, the NWSEC is of the opinion that the data sources and analysis undertaken to determine Weeds of National Significance is the most comprehensive available and is sufficiently objective as to be clearly defensible.

The Committee acknowledges the limitations associated with compiling the final ranking in what is a ground-breaking undertaking. It is hoped that the process will be further utilised by administrators and policy-makers involved at all levels of land management decision-making throughout Australia, and that future work will progressively refine the methodology.

Weeds of National Significance status will bring a weed species under national management for the purpose of restricting its spread and/or eradicating it from parts of Australia.

Funding decisions for Weeds of National Significance from the Natural Heritage Trust - National Weeds Program and other government sources is a separate issue and distinct from the determination of Weeds of National Significance, beyond the control of the NWSEC.

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List of Weeds of National Significance