A risk assessment of the tropical wetland weed Mimosa pigra in northern Australia

Information on the biology and management of mimosa, Mimosa pigra L., has been collated and analysed in a risk assessment in the regional context of northern Australia. The aim was to provide guidance for environmental managers and researchers to collate and assess relevant information to assist management decisions relating to areas at risk of invasion and consequences of invasion. The major wetland categories in northern Australia are briefly described and a summary of the effects of mimosa on native fauna, flora and socio-economic factors is presented. The current and potential distribution of mimosa in northern Australia is discussed, along with factors influencing establishment, density and distribution. The prediction of the potential distribution compares annual rainfall zones with CLIMEX modelling, overlaid with potentially vulnerable wetlands and land tenure. These are discussed in the context of the current management of mimosa in northern Australia. Uncertainty and information gaps relating to the extent and effects of mimosa are also highlighted. An estimated 4.2 to 4.6 million ha of wetlands in northern Australia are under threat from mimosa, though the actual area of suitability within this range is unclear and dependent on further research. Resolving such uncertainty is seen as a priority task, as it will provide a stronger basis for strategic research and control activities.