The establishment of species in ecosystems they are not native to; see, for example, Russell-Smith et al. (2004) J. Biogeog. 31, 8 on the invasion of rain forest into eucalyptus woodland in Australia. Campbell et al. (2002) J. Biogeog. 29, 4 outline a methodology which might be able to be used to predict invasions by alien plant species. ‘Humans cause invasions, humans perceive invasions, and humans must decide whether, when, where and how to manage invasions’ (Richardson et al. (2008) PHG 32, 2).