Recently there has been a small dust up between orthodox and heretical invasion biologists, ecologists and environmentalists interested in the effects of novel species establishment on ecosystems. What this means is that differences of opinion mostly and occasionally fact are being emphasized in the general media in order to boost readership because the general public loves nothing more than to watch a brawl. The non controversy concerns the efficacy of current invasive species research application in the management of ecosystem resources. Simply put they are arguing about whether weeds introduced purposefully or accidentally to a neighbors garden (system) matter. In some sense this is a small version of the climate debate fueled by the confusion over science based fact and belief based opinion. In both cases, then public is allowed to confuse fact with opinion because the resulting controversy sells.
I offer as a postulate that when you change a complex system you will change the output. When you plant hectares of corn, you change the complex system of the place and you change the output (yield): more corn less everything else. When you cut down all the trees in a plot of land and pave it over to build a mall, you change the dynamics of the system that was in place and change the output from potential outputs to specific consumer goods. The resulting change also includes some external costs onto neighboring properties which the mall owner and users willingly choose to ignore because of course they want to reduce the costs of the services provided. The mall user wants convenience, so loss of immediate biological diversity is transferred away from the site; the user wants goods at the best possible price so storm water management issues are begrudgingly addressed if at all and if addressed paid for by everyone else. Let me be clear, the change to the ecosystem could be a mall, a campus, a housing development, a hospital, ornamental landscape or farm (organic or otherwise) or any other kind of focused resource. Let me state this again: when you change, alter or modify a complex system whether purposefully or by externalizing costs elsewhere you change the output of the system.
Now let's talk about adding new species to an existing complex ecosystem whether intentionally or through closing our eyes to accidental escapes. The nature of complex systems guarantees a future change in the output of the existing system. The further out in time the less we are able to predict the effect of the change. So we are left managing the present. We do this by looking at the near term potential of a ecosystem and changing it to produce specific outputs (yield). Because we do these things in a sense to add human value we also while making the change externalize as many of the cost of the change onto someone else's ecosystem because that is how one makes a profit - transformation of long-term potential to immediate gain.
Thus the two sides of the invasive species debate are not talking with in the same time scale. The traditional invasion biologists are looking towards loss of long term potential output, while the novel environmentalists are considering the gains of near term definite outputs. The debate gets further confused when the native-exotic conversation is over-laid onto the debate. Now along with confusing scales of time we assume everyone has the same definitions of native and exotic. For example what exactly is native within the invasive species debate at CO2 levels of over 400 parts per million?
When we change or alter an ecosystem because of human need or profit (externalization) we make it possible for new species to establish without actually having any idea of the long term repercussions to the services we now take for granted. New species that alter the ecosystem interactions or relationships quickly change the output of the ecosystem. There are no species in a system that have no impact on a system at some level of intensity. To imply that invasive species are a non issue is akin to claiming weather patterns that change over time do not impact crop outputs.
The establishment of new species in an ecosystem changes the ecosystem forever...there is no going back (part of the definition of a wicked problem). Just as the farmer knows this and starts his day controlling his ecosystem, the field, by removing and preventing the establishment of novel species (weeds) so the invasion biologists works to understand how to manage the impact of the ever increasing number of exotic species into natural (potential) ecosystems. Just as the home gardener understands that certain species negatively impact the potential of the home's landscape, so the natural area manager is concerned about invasive species impacts to his or her landscape.
Do not get caught up in the current debate fostered by our general public interest in school yard fights. There is no there, there, to this fight. As surely as human disturbance will create a state of co-evolutionary pressures from invasive species that take advantage of our chronic plowing of the earth, so we must continue to study through research the impacts and effects so that we can effectively manage our landscapes, managed and natural