Aim  Anthropogenic introductions of Australian Acacia spp. that become classed as alien invasive species have consequences besides the physical, spatial and ecological: there are also cultural, ethical and political considerations that demand attention from scholars in the humanities and social sciences. As practitioners in these disciplines, our aim is to reflect upon some of the social and conceptual ideas and attitudes relating to the spread of Australian Acacia spp. around the world. We therefore provide a longer-term historical and philosophical perspective using South Africa as a key example. We explain some of the cultural aspects of Australian acacias, relating them to history, philosophy and societal ideas that were once, or indeed remain, important, either regarding their exportation from Australia or their importation into other countries. Focussing principally on South Africa and Australia but including brief references to other locations, we augment the literature by making connections between acacia introductions and environmental ethics and aesthetics, national and environmental history and symbolic and other discourses. We evaluate a number of the cultural and philosophical dimensions of invasion biology as a societal response and explicate the interesting contradiction of Australian acacia introductions as simultaneously economically valuable and environmentally transformative in South Africa.
Location  South Africa, Australia, with references to other parts of the world.
Methods  This paper has been written by an interdisciplinary team (two historians, two geographers, a philosopher and an ecologist) and is conceptual and historical, conforming in language and structure to the humanities style. It relies on published and unpublished literature from this disciplinary domain and the critical evaluation of these sources.
Results  Many Acacia spp. from Australia have been introduced around the world, generally guided in different eras by a variety of overarching mindsets, including the colonial ethos of 'improvement' (1800s to mid 1900s), an economically driven mindset of 'national development' (1900s), by a people-centred frame combining concerns of environment and livelihood in 'sustainable development' (1980s onwards), and an aesthetic ethos of ornamental planting that surfaces in all periods. The newest ethos of controlling or managing alien invasive species, a normative attitude deriving from the burgeoning of invasion biology, has more recently shaped the ideology of these plant exchanges and sharpened the focus on species that may be simultaneously both weeds and commercially valuable crops. Our perspective from the humanities and social sciences calls for a more transparent approach that clearly acknowledges such contradictions.
Main conclusions  We conclude that the global experiment of human-mediated Australian acacia introductions raises a number of issues that reflect changing societal concerns and demand attention from scholars in disciplines apart from the natural sciences. Here we highlight the impact of historical context in plant exchanges, the history and philosophy of science as it relates to invasion biology, and changing - sometimes divisive - societal priorities in terms of aesthetic, economic and conservation values. In particular, the case of Acacia spp. in South Africa highlights the contradictory aspects of introductions in that some species are both commercially important and environment-altering invasive plants. We argue that the contribution of disciplines beyond ecology to the debates about the invasive status of acacias enlarges our understanding and provides useful insights for botanists, foresters, managers and policy makers.