The Resilient World (Does Invasion Confer Resilience?) speaks to me directly. As with all wicked problems, the complexities of the problems at hand overwhelm the casual observer. Almost instinctively we find one counter example and claim significance. Waugh identifies a key issue of factual convenience in invasion biology. He writes that, for many of us, all it takes is "…one out of one hundred biological invaders…" to provide objective balance in the face of "…overwhelming evidence to the contrary."
"Ecosystems", Waugh writes, "adapt to external conditions. Biological exchange is part of that process." Adaptation is a hall mark pattern that emerges out of complex systems. The nature of ecological systems is one of semi-autonomous entities each doing its own "thing" it different physical and temporal scales. The resulting interactions create a feedback system, a pattern of activity, we call adaptation.
This is not a linear operation. We cannot push one part of the ecosystem and predict the outcome exactly or specifically. Unlike in our cars, for example, which are complicated systems but not complex, wherein, when we push down on the accelerator, we "know" (predict with certainty) that the car will go faster, ecosystems do not respond with any absolute predicative certainty. We know that if we cut all the tress down, there will be no trees, but we do not know for sure that the other large scale results will be. We cannot say for sure whether we will create a meadow, a desert, or something completely devoid of life. We can list the probable outcomes within a range of possibilities. The lack of certainty drives our desire to "balance" the fuzziness with statements of fact however biased they might be. We turn to the expectation to prove the rule because it is comforting, and allows us to concentrate on more mundane activities such as preparing our tax returns or deciding which channel to watch.
Added to out discomfit imbued by uncertainty, is the Aristotelian way of seeing the world which reduces everything to a category of either or (A .or. B; beneficial .or. harmful to human need). Invasive species must accordingly be either good or bad. Because of the factual convenience some claim a "good" state from invasive species thereby negating the demonstrable harm in spite of a preponderance of evident to the contrary. On the other hand, there is a similar all or nothing state of mind held by those who, in Waugh's words, try to mitigate or prevent the "collapse of tropic levels and simplification of ecosystems, resulting in loss of diversity and thus [the] loss of adaptive capacity."
What we need to do, is to think of invasive species in terms of wicked problems and to apply "fuzzy" logic to the issues of invasion biology. Fuzzy logic is thinking in terms of A .and. B, not A .or. B. Fuzzy logic asks how many bits of an apple can one take before what is left is no longer an apple. Applied to invasive species we might ask how much in some percentage sense harm and benefit a particular species has on a specific region at a certain time. Using fuzzy logic we could assign a metric to each species of jar/benefit based upn a specified ecosystem. We could model this metric through time adjusting our inputs and observing feedbacks as we nudged - "engineered" - the system. We xould explore parameters of resiliency noting events that push the ecosystem towards a transition state that might either create a novel ecosystem or cause the system to crash.
Waugh also refers to the by now deeply imbedded problem of native versus alien, but that is another blog for another day. Deciding what is native in a world with rapidly changing climate, atmospheric gas rations and rising water levels is more than I can address in 600 words or less