The wicked inconvenience of invasive species is wrapped up in definitional fuzziness. Bertrand Russell must of been channeling invasion biology when he wrote that "everything is vague to a degree you do not realize till you have tried to make it precise, and everything precise is so remote from everything that we normally think, that you cannot for a moment suppose that is what we really mean when we say what we think." (Bertrand Russell. 1918. Logic & Knowledge: The Philosophy of Logical Atomism )
In many debates the conversation rarely moves past the definition of the word invasive, never reaching the dark recesses of taxonomy and the outer limits of agreeing on what exactly a species is. Because the interest groups, both those worried about invasives and those who are dismissive of any concern, stay far away from the tail-end of the general definition of an invasive species - the part that refers to harm. The U. S. Executive Order 13112 defines an invasive species as “an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.” In the Executive Summary of the National Invasive Species Management Plan (NISMP) the term invasive species is further clarified and defined as “a species that is non-native to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.” As one of the authors of the white paper referenced in the link above, I remember the conversations surrounding the challenge of what we mean and what we do not mean by the term invasive species. I also recall the problem of dealing with the idea and consequences of harm. In a real sense, it for many stakeholders it comes down to the old adage that one knows harm when one sees it.
So what exactly is harm? The word harm comes to us through the centuries from the Old English word hearm that is related to Old Norse's word harmr meaning grief and is related to the Old High German word harm which is translated by our modern English word injury. It is interesting to note the Old Slavonic word sramǔ which is rendered by the English word disgrace. Today the modern English noun, harm, is defined as 1. a physical or mental injury or damage or 2. a moral evil or wrongdoing. Harm can therefore be any physical damage to the body caused by violence or accident or fracture. By analogy or inference we can think of a landscape or ecosystem as a body and see the extension of meaning as a species introduced by human activity displaces indigenous species. Harm can also be defined as an occurrence of a change for the worse (the act of damaging something or someone) which on the surface seems to succinctly explain the invasive problem but in itself begs the question as to how to assign a value to worse. Again we tend to resort to know it when we see it to escape the tedious process of actually thinking through the logic of the definitions.
Armed with the above definition it is clear that the problem is one of valuation. How does one assign a value to change? What do we mean by change for the good or change for the worse? If I see a tree falling in my direction , self-preservation assigns a value of bad and I move to correct my path so as to disallow a presumed negative outcome - on other words I get out of the way. If I have a tree leaning towards my house and I notice that each month it leans a little more, I will assign values to the potential damage to the house that may come at some point versus the cost of being proactive and cutting down the tree or if possible staking it. I am now performing complicated future value calculations taking a discount rate and considering opportunity costs. I am assessing risk.
In the examples above, I am the only decider in the equation. The problems and solutions revolve around me and there is no other human parameter to consider. However if we add another person to the equation the process of valuation can become complicated quickly and gives rise to one of the reason we have societal laws. If the leaning tree is not on my property, and for example is a walnut, my neighbor for his own economic reasons may wish to let the tree grow to harvest the wood at a later date when the market return is better. Short of altruism or laws his concern is not harm to my house. It is more profitable for him to externalize the problem onto me. Of course he needs to figure the potential loss of access to when it falls onto my property.
Now consider the problem that arise if I decide to grow and sell a non native bamboo such as Phyllostachys aurea and my reason to sell this plant are 1. it reproduces with little input or effort from me and thus is easily propagated for sale and 2. is easy to market because it grows anywhere and creates quick landscape screening - a ready market for my business. I am making a profit, and from this profit am able to afford health-care. The little issue of its spread onto my neighbors land can be seen as my "free" gift to him or her. I am externalizing some of my production costs because I do not spend time or resources controlling the movement of the plant through the local landscape and ecosystem. I rationalize this by noting how wonderful it is to be able to afford health-care because of this wonderful non native species. My calculations are all done in near time; I benefit right now and tomorrow and am therefore convinced of the overwhelming evidence of positive valuation of the introduction of this species. In fact as far out as I can see the profits from this species will allow me to set aside fungible resources to deal with and hazy problems that may arise in the distant future from any unexpected challenges to the community.
Now my neighbor happens to be interested in back yard habitats and butterfly photography...it is how he or she makes her mortgage payment. The destruction of indigenous biological diversity is bad enough as my plant spreads by sales into common areas such as public parks, but the direct incursion of my profitable plant on to his or her land is intolerable. However I make money by not spending it on control. If I had to spend the amount of money necessary to keep the plant from spreading my profits would go down. My neighbor is of course not interested in my profits which for him or her are realized as costs. In other words my positive valuation becomes their negative valuation. My good species is their bad species. at the neighbor to neighbor level this is fairly straightforward, but when applied to ecosystems, landscapes and communities at large the valuation process spins out of easy linear consideration.
Keeping the above, contrived situational valuing processes in mind, we need to consider the problem of change in space and in time. Change in and of itself is dimensionless. Change is the result of an operation. Without change there is no life as we know it. "Πάντα ῥεῖ καὶ οὐδὲν μένει - All is flux", said Heraclitus, and any work to hold back change has a cost. Change is geography, change over time lead to change in resource service mix and output possibilities. However doing nothing about change is not an answer that leads to long life. A farmer who says that there is no point to removing weeds in the field every day because the weeds just come back soon as no crop from which he can harvest food. In essence the farmer spends resources, lowering profitability, fending off the incursion and establishment of unwanted species who from experience he judges to have a negative value. The farmer takes a lower short term profit because if in the long term he chooses to do nothing he knows there will be no benefit.
Harm in invasive species is reduced to a calculation of near and long term benefit that must be redefined continuously. This makes for difficult policy conversations and the difficulty in turns leads to implications in order to enable movement towards predefined goals. The wicked inconvenience of invasive species lies in part in our inability to address how much harm is permissible, how much change can we permit and who will pay to stop a tree from falling or an ecosystem from collapsing. The cost of preventing can be compared with cost of the benefit lost and a near term decision made, but ho to calculate the loss of future possibilities. For example, the emerald ash borer, an invasive species will reduce the number of ash trees to near zero. Baseball bats are made from ash trees. What is the value of future loss of yet unmake baseball bats? What other as of yet unknown benefits might come from a future that now has no ash trees to speak of?
When considering harm how do we value biodiversity's future possibilities against present needs? By homogenizing the landscape, we introduce predictability into our lives many of which because of our urban lifestyles are rife with landscape illiteracy. Who has the time to learn about the interactions between species and which ones may bite or give a rash? If we introduce the same workhorse species around the world then we can presume a certain amount of predictability and therefore unthinking safety as we move about the landscape absorbed in our pursuit of life. Invasive species are co evolutionary partners with mankind. Invasive species are biotic ploughs that chronically disturb the land around human settlements and grind down biological diversity brining a predictable simplicity. This simplistic landscape buys enough time in theory for humans to life in relative safety and work to find alternative resources to provide medicine, air and clean water as the natural ecosystem declines, or so the short term decision model seems to suggest. Humans will extract enough profit to deal with any problem that arises in a distant opaque future.
To some extent it seems that harm is in the eye of the beholder. Harm that comes today trumps the harm that comes tomorrow for logically if you do not live through the day the problems of tomorrow will not matter to you. Because we use a hyperbolic function to assess the value or size of harm in time, tomorrow's problems which are of the same size or value as today's look smaller to us. When it comes to deciding the value of a future decision we find ourselves in a negatively curved decision space. The decision seems to boil down to how much known resource extraction or change is of a benefit now versus how much will this change possibly, maybe cost us then in inaccessible opportunities. This simplistic equation reduces the question about preserving biodiversity to one of a question of preserving the crown jewels of Great Britain; what is the cost of protecting them versus the worth of the metal and stones today.
To all of the above we now need to add the layman's confusion that rises between assessing risk of harm with managing the risk of harm. "Risk assessment is the determination of quantitative or qualitative value of risk related to a concrete situation and a recognized threat (also called hazard)" according to Wikipedia. Explicit in the definition is the idea of concrete situations, and not therefore, hypothetical maybes. The Wiki entry continues, "Quantitative risk assessment requires calculations of two components of risk: the magnitude of the potential loss and the probability that the loss will occur." The idea of probability is the most slippery deeply inset idea behind risk. It destroys our notion of a world of clearly defined possibilities upon which we build our entire decision making structure . We assume that the world can be defined into convenient terms of absolutes when in actuality we live in a probability universe. By assigning either a value of good or bad we set ourselves up for irrational arguments at the fuzzy boundaries of the problem. To assess the risk of harm in the future from an introduced species we enter the world of probabilities, an alien ecosystem to many of us in the domain of the general public. A challenge in risk management is finding the means to measure potential loss and probability of occurrence. How do we go about measuring the potential loss caused by feral cats let loose upon our common public areas or our private garden spaces for instance?
Ruminations on the Complexities of Invasive Species