Michael J. Coleman

The Risks Associated with Weed Spread in Australia and Implications for Natural Areas

ABSTRACT: Most recently naturalized weeds (invasive non-native plant species, or species growing outside their natural range) in Australia are still only locally distributed, so it is critical to identify the pathways by which these and more widespread species are most likely to spread and to identify the domestic sources from which they are most likely to emerge. Our research sought to identify which weed sources and pathways account for the majority of weed ingress, which pathways pose the greatest risk, how these risks are changing, and how pathway management strategies might be improved. These questions were addressed through a review of literature and a survey of Australian weed experts. Twenty-four sources and 17 natural and human-assisted pathways were identified and assessed. The most significant weed spread pathways in Australia appear to be the trade in ornamental plants and movement of machinery and vehicles, while other important pathways include fodder trade, aquarium plant trade, agricultural produce, and water. Economic and demographic trends, and changing climate, are likely to contribute to growing importance of a range of weed spread pathways in the future. Pathway risk assessment makes it possible to target scarce weed control resources, policy measures, and research efforts by highlighting the pathways that have the greatest potential (in terms of likelihood and potential magnitude) to spread weeds, now and in the future. Similarly, it informs natural area managers as they instigate control and management tools that address the highest risk means by which weeds might enter and spread through their area of responsibility.

Effectiveness of best practice management guides for improving invasive species management: a review

Best practice management (BPM) guides are a key component of invasive species extension in Australia, and are becoming a more important way of reaching land managers with comprehensive invasive species management strategies. However, little is known about the quantifiable benefits of these guides as a stand-alone extension approach, or in comparison with other approaches. We therefore reviewed the existing literature to determine when this form of extension was appropriate, what determines the success or failure of BPM guides in facilitating best practice invasive species management, how effective they had been in the Australian context, and what methods were available to evaluate BPM guide effectiveness. BPM guides are most appropriately used in support of other forms of extension and enforcement of invasive species regulations; as a cost-effective alternative to more labour-intensive extension techniques; or in bringing together disparate information in a single comprehensive source for land managers and extension practitioners. They appear to be most appropriately distributed at mid- and late-stages of the invasion curve. Limited quantitative evidence of the effectiveness of BPM guides for invasive species in Australia is available, although there is a consensus that these materials are popular among target audiences, despite a range of studies having shown face-to-face extension to be more effective. Unfortunately, many factors make successful evaluation of a BPM guide difficult, such that extension professionals are less likely to consider the possibility of evaluation. However, we argue that extension professionals need to consider evaluation of written BPM guides, where time and funding makes this possible. Ideally this will involve formative evaluation to improve the content and messages of the guide, as well as summative evaluation to determine its effectiveness among the target audience and for the target species. We also suggest a range of economic evaluation possibilities that warrant further exploration and trial.