On a morning run I came across a sign in the park informing me that the city was “helping nature by controlling invasive plants.” This process involves herbicides and machetes. My adopted city of Tallahassee is quite active in addressing invasive species. Laying aside the various concerns about herbicides, this raises many philosophical issues.
On the one hand, the phrase “helping nature” can be dismissed as a rhetorical device. It presents the destruction of invasive species as a benign act and, one might suspect, is intended to offset negative feelings some might have towards the use of herbicides. As you smell the chemicals and feel your skin and mouth itch a bit, you will know that this is all for the good of nature. On the other hand, it does imply a value position on what helps nature. Let us look at this.
Taken at face value, the implication of the sign is that invasive species harm nature and thus it is good for humans to kill them. An easy and obvious reply is that invasive species are also part of nature. For example, feral hogs, Burmese pythons, and Nandina are natural beings and they are, one would assume, not helped by being killed by humans.
A moral way to counter this is to advance a utilitarian argument: allowing the invasive species to thrive will do more harm to the ecosystem and its inhabitants than killing them. As such, killing invasive species is the right thing to do (at least in such cases). This approach would allow for invasive species to be left alone if their presence created more good than harm for the ecosystem.
While this does seem to be a reasonable approach, it does suffer from an obvious practical concern of doing a rational and informed calculation of what is likely to be best for nature. Humans have generally proven bad at this—so such assessments need to be critically assessed.
Another counter to the idea that we should “help nature” is that nature (taken as a shorthand for the ecosystems and their inhabitants) has always involved species migrating to new areas. Animals, obviously enough, do travel and have spread around the world. Plants can also spread far and wide, such as when seeds are inadvertently transported in the stomachs of birds. Assuming that life originated in one or a few locations, then this has been going on since the beginning of life on earth. And it continues to this day; the natural world is not static, and species are constantly on the move.
I am not arguing that this feature of nature is “good” because it seems to have always been (that would be a fallacy). Rather, the point is that is how nature works: species moving is natural and hence interfering with it does not really “help nature.”
Yet another counter to “helping nature” is to note that the idea of helping nature would seem to entail that nature has a purpose, goal, or end that we can assist with. The idea of nature having an end is well known in philosophy, although it is generally rejected these days.
But Aristotle famously claimed that all natural beings have ends, thus arguing for a teleological reality. To use a simple example, an acorn has the purpose, goal, or end of becoming an oak tree. If one looks at nature in teleological terms, then we could help nature by assisting it in achieving its purpose. This matter can get complicated if natural being have competing ends, but it would make sense to help or harm nature if one holds to a teleological view. There is also a religious option.
One could, of course, embrace a religious view that grounds a teleological view of the natural world. One could embrace, for example, the existence of a goddess of nature and thus help nature by helping her achieve her ends. Or one could accept the existence of God and help God by assisting the natural world achieve God’s ends. One would just need to sort out what the deity wanted to help nature. But some might find such supernatural things problematic. In that case, one could turn to human values.
If we accepted a teleological view of nature, then we can argue that we should deal with the invasive species they introduced by accident or design—such as cane toads, rats, mussels, and many plants. We are accountable for our actions, perhaps even when they are unintentional. One could even argue that what we do is artificial rather than natural, hence we need to undo the unnatural things we have done or allowed to happen. Interestingly, this would seem to entail that we are the most invasive species of all and thus we should restore ourselves to our original habitat and return the world to some specific time of species distribution. Interestingly, this does make this sort of conservation analogous to the conservative world view in politics: a desire to restore the world to some preferred (perhaps imagined) past state of things. The obvious problem, given the endless change, is deciding on which time defines the “correct” past state of things. This leads us to human values.
In general, species are condemned as invasive based on their impact on human beings. For example, we North Americans do not usually label our dogs as an invasive species. This is not because our dogs are original inhabitants of North America, but because we like dogs. Recently arriving species generally get labeled as invasive when we do not like what they are doing. For example, Floridians generally do not like the non-native species that are overrunning bodies of water in the state. This is because of the impact they have on us. This is analogous to how people look at the migration of other people: people are fine with people they like coming here. But they get very angry when the people they think should not be here come here. And, of course, they slap negative labels on them and argue for their removal. So, it is essentially a migration thing. But let us get back to non-human species.
Since I do think humans matter morally, I do think that we have the right to consider the impact of species on our well-being. But we should be honest when we do this: we should not claim that we are helping nature, we should own the fact that someone is doing what they claim will benefit them. This is something to be addressed in ethics, sorting out what is right based on the correct moral theory (if there is such a thing).
Being a self-interested human, I do agree morally with some efforts to address species we call invasive. For example, the park near my house is infested with tung trees. These trees were introduced to the United States intentionally to produce tung oil. This industry failed, but the trees spread throughout Florida—including where I live. I dislike the trees for two main reasons. The first is minor; their fruit presents a small falling hazard. The second is that every part of the tree is poisonous. The leaves can cause a reaction like poison ivy and a single seed can be a fatal dose of poison. I do recognize they are as much a part of nature as I am and hence do not argue that they should be removed because they are not native. Rather, I am fine with their removal for the same reason I would be fine with removing broken glass from the park: they are a hazard.
To close, merely being invasive would not warrant the removal or destruction of species in an area. Otherwise, we would need to be removed or destroyed in most parts of the world. Rather, this is a matter for moral (and practical) assessment. Talking about “nature” and labeling species as “invasive” is mostly a matter of rhetoric and we would be better off being honest about what we are doing and why.