Kakadu National Park Landscape Symposia Series 2007–2009

2.4 WoNS species and strategic weed management in the Northern Territory

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  identification of weed management issues
  
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  assessment and prioritisation of weed management issues
  
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  development of cooperative action/management plans
  
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  implementation of coordinated action/management plans
  
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  encouragement of participation in action/management plans
  
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  development of weed management legislation and policy
  
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  enforcement of weed management legislation
  
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  provision of training, education and awareness in relation to weed species and management requirements
  
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  conducting of research and development in relation to weed impacts and management
  
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  development and maintenance of partnerships
  
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  provision of resources or assistance in accessing resources required for management
  
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  reporting progress against programs aims and objectives to funding providers.
  

Looking at the example of mimosa we see that the species is declared a Class A (to be eradicated) or Class B (growth and spread to be controlled) weed in specific areas of the NT according to the plants current and potential distribution. (Mimosa is also classified a Class C weed (not to be introduced) in all of the NT).

Weed management plans developed by the Branch provide detail specific aims, objectives and management requirements in relation to the particular weed species and to where these requirements apply.

The NT Draft Mimosa Management Plan for example indicates that in areas classified as Class A/C the aims and objectives are based around the principle of eradication and preventing further introduction. In areas where the plant is classified as Class B/C the aims and objectives are based on preventing spread and reducing the impact of well established infestations.

In more detail, the NT Draft Mimosa Management Plan aims to limit the impact of mimosa on the natural environment, the NT economy and social and cultural land uses by:

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  defining the management obligations which apply to all land managers and land users in the NT, which will form an integral part of the strategic management of mimosa across the Territory
  
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  providing information on actions required to meet defined management obligations.
  

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  eradicating isolated plants and outbreaks
  
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  implementing early detection and eradication programs
  
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  designing and implementing a seed spread prevention program
  

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  eradicating isolated plants and outbreaks
  
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  implementing early detection and eradication programs to find newly established plants and outbreaks, for eradication purposes outside core infestations
  
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  active containment of major infestations (eg though the implementation of grazing land management principles and buffer establishment and maintenance)
  
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  minimising further seed production
  
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  designing and implementing a seed spread prevention program.
  

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  developing and maintaining an ongoing monitoring program;
  
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  maintaining an accurate record of control methods applied and results achieved for possible collation at a Territory level
  
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  evaluating the efficiency of control and containment programs over time.
  

We also have the situations where weed species identified as priorities across the regions of the NT vary due to the range of environments encountered and as such a species identified as a priority in Darwin region (eg mimosa) will not necessarily be a priority in Alice Springs. This assessment is made through the use of the NT Weed Risk Management System.

Accordingly priority species and their associated aims, objectives and management responses to various weed management issues vary across the NT. The principles of the National Strategy, however still apply.

2.5 Regional weed management: Darwin region

Looking closer at the regional situation, in particular the distribution and risk posed to the various catchments, we may now also find that the current situation varies in regard to the particular weed species being considered. The weed species may be well established in the catchment, the species may be present at a very low level in the catchment or the species may represent a clear threat to the catchment. Accordingly our aims, objectives, responses and ultimately our level of resource allocation will vary.

Again taking the example of mimosa this is clearly the case considering the current and potential level of infestation. Currently there is approximately 140 000 hectares of mimosa in Darwin region, an area comprising 18 catchments and containing over 1.2 million hectares of vulnerable wetlands. Of these 18 catchments, four are completely free of mimosa, seven have a very low level of infestation and the remaining seven have varying degrees of infestation. As expected, the aims, objectives, responses and ultimately our level of resource allocation vary accordingly.

Figure 1 illustrates Darwin region mimosa management activities, aims and objectives in relation to the current distribution of the species (shown on the underlying catchment map of the Top End).