A Historical Perspective on Plant Invasion in Australia

Australia’s separation from other land masses has resulted in the evolution of flora and fauna in relative isolation. The arrival of Europeans some 230 years ago marked the beginning of a mass invasion of the continent by alien plant (and animal) species from across the globe. These mass invasions have had profound effects on the Australian landscape and its native species and have required significant management interventions. In this chapter, we present an overview of the history of alien plant invasions in Australia and the scope of the current situation in terms of the number of species introduced. Seven case studies illustrate the nature of the invasive weed issues and the actions undertaken towards management. Case studies include Australian Weeds of National Significance (WoNS) (Chrysanthemoides monilifera subsp. rotundata, Lantana camara) and environmental and agriculturally important invasive plants (Opuntia inermis, Opuntia stricta, Echium plantagineum, Cucumis myriocarpus, Citrullus lanatus, Andropogon gayanus) as well as recent incursions (Bassia scoparia). Each case study outlines the impacts and risks associated with the invasion and presents the unique management approaches adopted - asset protection, biological control, successful eradication and ecosystem transformation. Several case studies draw comparisons between the establishment and persistence of alien plants in Australia and their native ranges and provide important clues on key traits that contribute to their successful invasion. Results to date have shown that the number of introduced plants to Australia has increased exponentially across most states and territories, particularly in recent years. Targeted control strategies for some WoNS such as Chrysanthemoides monilifera subsp. rotundata have been successful due to significant investment in the study of weed biology and physiology and subsequent development of effective integrated weed management strategies. The management strategies for several WoNS and invasive plants are evolving, through continued involvement of local, state and federal government and nongovernmental agencies and researchers to identify more effective control strategies. Lastly, future management challenges are described, including the expanding alien flora, the potential impact of climate change and risk management associated with weed incursion. Unique Australian insights can provide potential examples for other countries facing similar challenges as alien plants are now a global problem.