Environmental issues

Pests and weeds

Selecting sites for protection of environmental assets

The list of assets at risk from lantana invasion provided the basis for the next step of the plan development, ranking sites for control regardless of land tenure.

Site selection process

The site selection process aimed to ensure that control is undertaken in areas where the outcomes will have the greatest benefit for biodiversity. It ensures efficient use of resources in areas that have the greatest likelihood of successful control and recovery of native species. Sites were assessed based on the following three criteria:

  1. the ability to achieve effective lantana control at the site while minimising off target impacts, particularly with respect to protecting the environmental assets at risk,
  2. the degree of impact of lantana at each site, and
  3. the condition of the assets present and the physical condition of the site.

1) Effective control

The ability to achieve effective lantana control at a given location is based on the feasibility of undertaking lantana control, particularly with respect to protecting the species at risk. The assessment range includes:

2) Impact

As the impact of lantana on the native biodiversity at risk will vary from site to site, the degree of impact at each site needs to be considered. To account for the variation between plants and animals at risk we have used two different criteria here. The level of the lantana infestation present and its proximity to the asset at risk. At some sites, lantana may only pose a threat (i.e. potential impact) to the asset at risk. A potential impact is where lantana currently poses a threat to assets, but has no current impacts, although it could impact on those assets in the future.

The assessment range for native plant species includes:

  • High: lantana poses a direct impact to the plant species at risk (i.e. growing within/over the species at risk).
  • Medium: lantana poses a reduced impact to the species at risk or threatens the native species in that it is within close proximity to lantana (i.e. growing next to the species at risk).
  • Low: lantana poses only a low threat to the plant species at risk (i.e. lantana is a distance away from the species at risk so that there is no immediate threat, but could still pose a threat in the short-term).

The assessment range for native animal species includes:

  • High: lantana poses a direct impact to the animal species at risk (i.e. displacing animals by restricting their movements); or indirectly through lantana out-competing native plants that provide a source of food or by lantana negatively altering the native habitat that these animals utilise.
  • Medium: lantana poses a reduced impact to the species at risk or threatens the native species in that it is within close proximity to lantana (i.e. growing next to the species at risk), with lantana invading the species' habitat or lantana altering the structure of the habitat.
  • Low: lantana poses only a low threat to the animal species at risk (i.e. lantana is a distance away from the species at risk so that there is no immediate threat, but could still pose a threat in the short-term).

3) Condition

Condition has three sub-components which assess the recoverability of the species at risk. The first two sub-components relate to (i) the condition of species, and (ii) the importance of a population to the native species’ overall survival. The third component relates to other threats present.

(i) Condition of the assets present at a site

The condition of the native species at risk is determined based on the population health of the individuals present at each site. Again, to account for the variation between plants and animals at risk we have used two different criteria here. Where adults and juveniles do not co-occur within a species the health of the individuals present was assessed.

The assessment range for native plant species includes:

  • High: majority of individuals within the population are healthy. There is a mix of age classes (i.e. seedlings through to adults).
  • Medium: mixture of sick/dying and healthy individuals and/or a poor age structure (i.e. few seedlings and mostly adults).
  • Low: majority of individuals sick/unhealthy. There is a limited age structure (i.e. no seedlings).

The assessment range for native animal species includes:

  • High: majority of individuals within the population are healthy. There is a mix of age classes (i.e. juveniles through to adults).
  • Medium: mixture of individuals in poor condition through to healthy individuals. There would be a poor age structure (i.e. few juveniles).
  • Low: majority of individuals are in poor condition. There is a limited age structure (i.e. only adults present with no off-spring).

(ii) The value of the site to the asset survival

The value of the site to the environmental assets overall survival was also considered. Factors taken into account include the size of the population (for example few or many individuals) in relation to its natural occurrence (for example some species only occur in small populations). To account for climate change, whether the environmental asset occurs at a site at the edge of its range or whether the site is an important corridor for the native animals at risk were also considered. To account for the variation between plants and animals at risk, again different criteria were used.

The assessment range for native plant species includes:

  • High: the site has one of the largest known populations or is important for the species (for example is an outliner population or an important corridor).
  • Medium: smaller or larger populations known elsewhere, important but not critical for the species survival.
  • Low: few individual plants only at the site, with larger populations elsewhere, site not important for the species survival.

The assessment range for native animal species includes:

  • High: the site has one of the largest known populations or is important for the species (e.g. an important corridor or breeding site).
  • Medium: smaller or larger populations known elsewhere, habitat important but not critical for the species’ survival.
  • Low: few individuals only at the site, with larger populations elsewhere, site not greatly important for the species survival.

(iii) Site condition

The physical condition of the site with respect to all other threats (e.g. land clearing, grazing, nutrient enrichment, human foot traffic, fire in certain cases etc) that may affect the success of the lantana control program in delivering recovery of the assets at risk is also considered. The presence of other threats to the assets that may affect the success of the lantana control program in the recovery of these assets was also considered. Reduction of all other threats is outside the scope of the Plan with the exception of other weeds which pose a similar threat. This criterion also indicated the level of resilience of a site and ranked highly those sites with a high level of resilience, given that these sites would have a greater ability to respond to, and recover from, future disturbances. The assessment range included::

  • High: lantana poses the main or only threat. Other weeds present are easily controlled or are at low densities.
  • Medium: some minor threats present, which will still be active after lantana control. Other weeds present are as difficult as lantana to control.
  • Low: significant threats other than lantana present (e.g. land clearing), which will still be active after or irrespective of lantana control. Other weeds present are more difficult to control than lantana.

List of sites considered in the plan

A list of ranked sites can be found here. New site nominations can also be made at any stage to determine additional priority sites for control.

Instructions for nominating a site

If you would like to nominate a site for inclusion in this plan, please download this template. Ensure that you fill in all sections of the template and submit it here. Please assign codes (high, medium or low) to each of the criteria outlined below. If you are unsure of what value to assign for a criterion or if more information is required, please indicate this within the template with the letters FIN (further information needed).

Page last updated: 26 February 2011