Following up on an opinion piece published earlier this year in Nature (subscription required), Matt Chew and Scott Carroll bring their argument to The Scientist, defending their position from the responses from well over a hundred ecologists.
The details of their argument are not that important, because what they miss is the big picture. Simply, their argument is completely anthropocentric in a couple of ways, and this is where they and the invasive species biologists who responded are talking past each other.
Chew and Carroll take the central position that it is nothing but anti-alien bias that makes most ecologists demonize invasive species. Their essay has almost embarrassing overtones (accusing other ecologists of “personifying and demonizing the unfamiliar”) of the type used by those who argue that those trying to prevent destruction of local habitats by nonnative species are anti-immigration nativists when it comes to humans too. This is a tired diatribe, one also used by species importers who are simply defending their own financial self interest, and often containing inflammatory terminology such as “xenophobes” to describe the scientists trying to preserve species diversity in fragile habitats. The very fact that Chew and Carroll interpret attempts to protect native ecosystems as “personifying” alien species trivializes their argument by showing that it is they who are anthropomorphizing.
Another huge weakness of their anthropocentric essay is the arrogant assumption that we are equipped to understand all the ecological ramifications of introduced species, including those not showing invasive tendencies. My own food web research indicates that ecosystem-level effects below the radar of human observers (because they involve small invertebrates, soils, etc. or happen over a longer timescale than that of a human generation) can occur with established species not currently considered invasive (generally due to lack of an economic impact).
Despite this, the great majority of ecologists who advocate control of nonnative species are focused on the invasive species that destroy native habitats and cause irreversible ecological damage. To answer the charge that Chew and Carroll (and their Nature co-authors) have unfairly declared invasion ecologists as anti-nonnatives, including noninvasive species, they simply respond that their characterization is correct, and all the letter-writers are wrong. This is patently absurd, of course, because one of the basic tenets of invasive species research is the “tens rule”, which means that only about a tenth of introduced species establish, and only about a tenth of those that establish become invasive. It is because those promoting the importation of species are so lousy at predicting which will become invasive (if they even care) that invasive species ecologists promote prevention as the better ecological and economic strategy than control.
Finally, their argument is essentially circular in that they state that once invasives are fully established and integrated into the community, they are an essential part of that community and thus should not be controlled because of unintended effects. Because they maintain we should not worry about those species that do not appear to be invasive to us (yet), it of course follows logically that no invader should ever be controlled because either they don’t matter, or they are absolutely essential to the ecosystem. Apparently there is nothing in between these two extremes, despite what we know about the huge complexity of ecosystems, which we are only beginning to understand ourselves. Again, this argument makes sense only from an anthropocentric perspective.
Even then, there are others who argue completely differently from the same perspective. Jeffrey Lockwood, entomologist-turned-philospher at the University of Wyoming, argues that a “sense of place” should inform our views on whether alien species (invasive or not) should be tolerated on the terms presented matter-of-factly by Chew and Carroll. He means that homogenizing the world through the distribution of certain species throughout the world diminishes not only local diversity, but global diversity as well. In other words, even if not a single species were driven extinct by alien species, their mere presence in a new habitat diminishes the wonder of worldwide habitat diversity, much as the presence of “strips” containing the same national chains in towns all over the U.S. diminishes our local cultural diversity.
Thus, even if one agrees with an anthropocentric position regarding alien species, there are quite divergent conclusions that one can come to. Chew, Carroll, and their Nature coauthors ignore these alternative ways of looking at the world, and Chew cynically comments on The Scientist rebuttal:
In that worldview maximizing beta diversity (in short, keeping different places different) is treated as a self-evident primary planetary objective; suppressing change detectable at any but geological timescales is another. But that worldview is unenforceable on the world. It turns out that most people want access to what most other people have.
Therefore, apparently, it is some sort of elitism to have Lockwood’s point of view. There is a somewhat disturbing element of — for want of a better term — class warfare here. In his commentary, Chew seems to be framing himself as an egalitarian defender of the little people who just want to share in the bounty of the more fortunate, while Lockwood and his ilk are snobbish in their desire to prevent the constant expansion of global commerce from overrunning nature. It’s as if we should abdicate on this issue because we cannot afford to strive for higher values than the lowest common denominator of what the masses want. It is a similar argument made by those who consider the arts, or space exploration, or ecological research in general to be a frivolous way to spend money. Ironically (because it is made by ecologists), it boils down to the pessimistic argument that humans should not bother striving to use our brains and culture to be something more than tribal exploiters of our environment.