Ruminations on the Complexities of Invasive Species

The blog posting, Biologists as engineers of the living world, offers an opportunity to expand on my theme of the wicked inconvenience of invasive species.[1] Should we engage in biological engineering to solve invasive species problems? Invasive species are a wicked problem, a type of problem that is found in many social and physical systems. A very well know wicked problem intrinsically related to invasive species is climate change. In two sentences I have described two complex systems that are regularly reduced or simplified into complicated explanations with associated multiple conflicting solutions. In a complicated system, on the other hand, the members or parts and their interactions or connections are equally important. Unless redundancy is built in, when one part or connection fails, the entire system fails. In a complex system on the other hand the members or parts are of no individual importance, and a loss of one is not critical. However, the connections are important and it is the loss of a connection or interactive pathways that can dramatically alter the whole system. In a complicated system simple rules give simple predictive results whereas in a complex system, simple rules result in unpredictable outcomes. 

Invasive species are, in some sense, a symptom of a perturbation in or a disturbance of ecosystems. Ecosystems are dynamic networks of interactions and relationships that are most assuredly not collections of static, predictable entities. One does not predetermine the exact flight path of a bee or the precise flow of a stream but rather one describes the most probable direction and boundaries in which the system may be found in the future. More specifically it is possible estimate the probability of certain outcomes weighing one against another but it is not possible to say for certain which outcome is certain in all cases for all time.

Ecosystems are also adaptive which means that their individual and collective activities, actions and behavior change as a result of inputs, interactions and behaviors. Invasive species are the result of some action or sequence of actions that result in the movement of one species into a new region. By definition, invasive species are the harmful-to-humanity, non-indigenous pathogens, plants or animals that are introduced as a result of human activity into a novel ecological system – into our backyards and homes. It is worth noting that as a rule it takes more than one introduction event, so the establishment of an invasive species through human activity enhances the portability of success. The complexity lies in part within the many assumptions that I just made in trying to define what the problem is, and I have not yet discussed cascading effects of species introduction on ecosystem services.

To engineer a solution, we start with an identification of a need or problem, and then work to develop a tool or process that becomes the solution. We try to economize costs, which usually but not always means some linear answer more or less in a straight line preferably with as few gaps as possible. A prosaic example is a plow. The need is to break up the soil and the ecosystem so that a food source can be easily planted. The engineered solution today is a metal shape that cuts or rips through the land in a straight line. The plow works wonders if you keep your eye on the goal which is to make planting easy and short term yields. At the same time the engineered solution creates unintended new problems such as erosion and soil nutrient run off. This is the fear inherent in the linear approach to biology.

The interesting side product of the engineering marvel we know as the plow is the ability to disturb the earth inexpensively, repeatedly and, therefore, chronically produce a disturbance pattern that favors certain species over others. And these species are either called weeds by farmers and gardeners or invasive plants by natural area managers and ecologists. This unintended product is possible anytime one applies linear thinking to non linear systems and is even in an ironic twist guaranteed by definition. The unexpected outcomes from engineering in a straight line should not be a reason not to consider engineering complex systems. Rather it is an invitation to think first and consider using applied complex system theory as an integral part of the engineering process. 

Historically, when faced by a problem in landscaping we engineer a simple, cost effective solution. Since landscaping usually includes plants, the landscape architect will engineer a plant solution if he or she can. The discipline of horticulture admits to the need from time to time of other expert professionals, but the ultimate design engineering rests with the landscape architect. The odds are slight that the client will pay for a comprehensive team of equals including hydrologists, ecologists, biologists, entomologist, and a dozen other specialties in advance of identifying a particular problem. In other words, we do not set out to identify potential problems that may affect the common ecosystem, but restrict of future externalities, our deliberations are directed to the landscape at hand to keep costs from quickly becoming prohibitive. And so we specify English ivy, Hedera helix, as a general purpose groundcover to minimize planting costs as well as maintenance cost in the near future. 

Linear engineered solutions are not solely found in ornamental gardening. In order to meet the insatiable demand for goods, the wooden shipping pallet is a simple engineered platform. Take a tree from the fields near where a product is made, create a pallet, and send the product on the pallet to a new ecosystem. Hidden on board on or in the pallet may be living hitchhikers foreign and deadly to the receiving ecosystem. This is straightforward, simple and deadly to ahs trees. The emerald ash borer is eating the ash trees of North America. The borer most likely arrived on wooden pallets or shipping craters which, had an interdisciplinary team been assembled might have been avoided. And with identification of a risk, protocols could have been put in place to reduce the risk of millions of acres of dead trees.

Biological systems may perhaps be engineered if we keep a few key things in mind. First complicated linear and determined systems produce controllable and predictable outcomes, while complex adaptive systems can produce novel, creative, and emergent outcomes.[2] Biological systems are complex systems of the latter type, and will require a sympathetic engineering strategy that changes some aspect of the system and then works with the biologic system while it adjusts to the change. The traditional assumption of straight-line thinking will be dangerous if applied to complex biologic systems. The dependable ascertain that every observed effect has an observable cause will lead inevitably to unintended consequences. A belief that the whole can be understood by taking the system apart and studying the pieces will tend to produce surprises many of which could be unpleasant. The problem of complex systems, the challenge of biology is that they are rooted in chaos theory and wickedly defy any predictive detail modeling.

We should not be afraid of engineering. We should be afraid, however, of treating biologic systems like cars. We can tool a solution to a door lock with every reasonable expectation of a predictable outcome; we cannot tool biologic systems in the same way and expect to predict the result. On the other hand, this is not a reason, to adapt engineering to a process of nudging complex systems, pushing their constraints, and observing the results in an endless dance with our universe.

[1] Link to multiple posting on the wicked inconvenience theme of invasive species: http://ipetrus.blogspot.com/search?q=wicked+inconvenience

[2] Jones, Wendell. "Complex Adaptive Systems." Beyond Intractability. Ed. Guy Burgess and Heidi Burgess. Ocotber 2003. Conflict Research Consortium, University of Colorado, Boulder, Colorado, USA.