Lippia in the Murray Darling Basin

The Cotton Cooperative Research Centre (Cotton CRC) and the CRC for Australian Weed Management held a meeting in 2002, which led to the formation of the Murray-Darling Lippia Working Group, now the National Lippia Working Group (NLWG).

Lippia poses a serious environmental threat to inland wetlands and floodplains.

It was soon realised that an up-to-date study of the distribution and economic impacts of lippia was needed.

The NLWG commissioned a study, funded by the Murray Darling Basin Commission (MDBC) which:

• quantified current lippia distribution
• reported on economic impacts in the rural sector
• evaluated environmental impacts.

The study was conducted through information reviews and field assessments, as well as meetings with stakeholders and focus groups.

Dr Judith Earl presented the findings in a report in 2003. The report highlighted issues that should be of concern to land users particularly in the MDB.

A summary of the report concluded lippia is found over 5.3 million hectares of the MDB and is present in each of the 19 MDB catchments, with those upstream the worst affected.

The report also found that lippia:

• has not invaded its full range
• spread and increase in cover is related to floods
• is spreading to hilly areas above flood levels
• costs the grazing industry in the MDB a conservative A$38 million pa in lost production, plus significant costs related to herbicidal control, clearing and infrastructure damage
• results in average de-stocking rates of 55-100 per cent in severely infested paddocks
• is considered to be a major threat to riparian and associated ecosystems because of its dominance over native plants
• is a significant threat to numerous wetlands in the MDB, including the Macquarie Marshes where it currently infests 10 per cent of the reserve.

The report found costs associated with loss of environmental services are estimated at A$1 800 million pa, and included:

• loss of biodiversity, perennial vegetation and floodplain area
• increased rates of erosion
• reduction in water quality.

The report also revealed:

• conventional methods of herbicide application and low density grazing do not provide effective long-term suppression of lippia
• because lippia can be managed by cultivation, there is pressure to clear and cultivate invaded forested land
• inundated floodplains that should be maintained as permanent pastures are being cultivated, leading to soil loss during flooding - such practice is not sustainable
• in riparian areas, there are no useful options for management.