Who's invading what? Systems thinking about invasive species

While invasive plant species have dramatic and varied effects, this paper examines the focus of this symposium on their "threat to native biodiversity and ecosystems". This claim implies that there is (i) an enduring something, (ii) it is native, and (iii) it is under threat from invasive species. I examine these implications in turn, first considering the role of the observer in invasion biology, particularly in preferring a nature characterized by stability rather than flux. Second, I examine the concept of "native" given that humans are thoroughly embedded within ecological systems. Third, I demonstrate how our exclusion of humans conditions us to consider invasive species a primary threat rather than one among many interacting causal agents of global change; in particular, recent evidence indicates that these agents, which include human-caused disturbances and global warming (not to mention human population growth and global trade), may overwhelm the effects of invasive species per se. For these and other reasons, some ecologists have argued that ecological change is inevitable and that our concerns about invasive species are unjustified. I discuss these issues and suggest ways for ecologists to conduct engaged research through appropriate advocacy and engagement with stakeholders dealing with local invasive species.