The human dimensions of invasive woody plants

This review of the human dimensions of invasive woody plants investigates the history and purposes of introductions, people’s perceptions of alien and invasive species and the impact of invasives on human activities. A perusal of the literature indicates that all aspects of the human dimensions of alien woody plants are highly varied and some are still poorly documented. Changes in the usage of species over time as well as conflicts of interest in relation to species introduction and biological control show that alien woody plants cause social and economic problems and conflicts related to human activities. These problems interact with a variety of human activities and these issues need to be addressed with care. Introduced woody plants Woody plants have undoubtedly been transported by humans for millennia and were an essential component of early agricultural societies. Indeed, many regions of the world, and oceanic islands in particular, would not have been colonised without the introduction of various crops, many of which were woody plants. In these early societies woody plants were a source of a wide array of basic materials as well as food. In more recent centuries the type of species translocated has shifted with an ever-increasing proportion being ornamental plants. Over the past two centuries many species have started to spread in their introduced ranges. Until relatively recently the majority of introduced woody species have been highly beneficial, if not essential, to humanity’s development, but now ever-increasing numbers of species are becoming detrimental to the maintenance of the earth’s biodiversity and to the well-being of human societies. This chapter attempts to unravel the relationships between humans and woody plants by looking at the changes in the introduction of species, the way they are perceived by different human groups and the impact these invasive species have on human activities. Finally, key examples illustrate how socio-economic factors and species utilisation may vary through time and that conflicts of interest between different groups often are inevitable. Historical perspective of plant introductions The history of woody plant introduction is closely linked with that of transportation and the European exploration of the planet (16–19th century) (Crosby, 1986). At various times in European history some individuals greatly enhanced the discovery and introduction of new species. For instance, in Britain Joseph Banks was instrumental in the setting up of Kew Gardens as a major centre for economic plants and in promoting plant prospecting (O’Brian,