Bushland Condition Monitoring

An environmental threat rating was assigned to weed species in 2006 as an integral part of the BCM method.  A single threat rating was assigned to each weed species for each BCM region, which coincided approximately with existing NRM regions. There had been no revisions of weed threats since the manuals were developed (though a consultation process with the regions was undertaken in 2012).

 

Since that time it became increasingly  recognised that this rating system was too general, and overlooks key determinants of environmental threat, namely rainfall, soil type and understorey type, which can vary significantly within an NRM region (or IBRA subregion). Therefore, the environmental threat ratings have been revised to account for these factors.

 

• As an example, Wild Oats (Avena spp.*) are a high threat in grasslands but a very low threat in forests, but currently have a low rating (1 or 2 out of 5) for all regions. Another example is Blackberry (Rubus fruticosus aggregate), which is a high threat in moderate to high rainfall zones, but a low threat in low rainfall mallee. Similarly, some species are highly threatening in coastal communities (eg Pyp grass (Ehrharta villosa*)) but not elsewhere. Rather than being ranked as a low to moderate threat (as is the case currently), this weed should be rated highly for coastal sand communities but low for non coastal communities.

 

• There have also been a number of weed species that have increased their abundance and distribution since 2006. For example, Buffel Grass (Cenchrus ciliaris*), and Silverleaf Nightshade (Solanum elaeagnifolium*) which were not recognised as high threats in 2006.

 

Under the new system, the BCM manual’s original criteria for assigning weed threat ratings are still considered valid, i.e.

 

• The weed’s degree of invasiveness into intact scrub

• The weed’s capacity to disrupt natural processes in bushland, and eliminate existing native plants, ie, its capacity to transform an ecosystem

• The degree of difficulty in controlling

 

These are explained in the table below: NCS BCM  Weed Threat Category Ratings