Invasive species - Russian pickler versus American Caterpillar - & the winner is?

Invasive species issues can be confusing, obtuse, complicated, ill-defined and contentious. And invasive species problems and their solutions become vaguer the closer one looks. Can a native species be invasive, and who defines this invasive quality?  Are all invasive species bad?  Are pet cats that become adapted to the parks and natural areas around our homes and fields invasive species?  If an invasive species has a economic or social benefit is it still an invasive species?  How long does an exotic alien have to be in the country before it becomes naturalized?  Sometimes it is helpful to limit the scope of inquiry so that the imponderables do not overwhelm the questioner.

In our garden, my wife carefully cultivates three non indigenous plants so that she can make home made organic Russian-style pickles; cucumbers, garlic and dill.  She also plants fennel, onions, tomatoes and peppers some of which, though American species, are not native to our east coast Mid Atlantic ecosystems.  With the exception of fennel, she has to yearly disturb the land in her small garden (cultivate) and re-plant each year from seed or bulbs she has collected the year before.  The fennel might be considered somewhat aggressive as it invades small sections of the flower bed nearby, but it confines itself only to those areas already massively altered and no longer in any sense a native species habitat.  From her pickling project point of view, the invaders are weeds and insects - insects we call by words not suitable to polite audiences; colorful vocabulary known well to organic and ornamental gardeners.

From the picklers point of view, even the aggressive non native weeds can be tolerated to some extent, but when the American caterpillar appears, it is a no-holds battle to the finish. The game is on; we have my Russian wife in a life or death match with the American champion tomato hornworm, Manduca quinquemaculata, (Lepidoptera: Sphingidae).  The ability of the hornworm to devour 5 foot tall tomato plants in a single bound (gulp) gives proof through the night, and day, that enternal vigilance and steely determination are the only tools. The voracious appetite of the caterpillar is matched by the eagle eyes of the organic gardener who refuses any and all chemical aid. Out she goes, her arm up to the elbow enclosed in the day's newspaper's plastic bag, to the pickling patch. Round one, sees her grab the hornworm; round two sees him grab bag; round three sees her jump a kilometer; and so on until the iron resolve of Russia conquers the stubborn American fighter. It is a classic collision of desires; natures systems arrayed against man’s needs.  (and makes it hard for me to know which side to cheer for)

Picture from: Moths of Southeastern Arizona: Sphingidae ( Hawkmoths )

In the case of the hornworm, the end game is "... a brown moth that rarely shows up on the top ten wish-I-had-in-the-garden list. The adult moth, sometimes referred to as a "sphinx", "hawk", or "hummingbird" moth, is a large, heavy-bodied moth with narrow front wings. The moth is a mottled gray-brown color with yellow spots on the sides of the abdomen and a wing spread of 4 to 5 inches. The hind-wings have alternating light and dark bands."    Relegated to second class oblivion and adult obscurity without the protection of charismatic status, the hornworm lacks a fan club clamoring for its immediate local victory.  The tomato hornworm caterpillar is labelled invasive because it comes into this little patch of Russian pickling heaven and negatively impacts, or drastically disturbs the carefully planned interconnections between selected plants and human dinner. The caterpillar is a classic, traditional example of an invasive species from a gardener’s point of view.

Photo by Fred Goodwin - 9/6/2002 Massachusetts Audubon Society  Ipswich River Wildlife Sanctuary Male

This limited area of consideration in our investigation of invasive species quickly turns fuzzy when we look at the dill plants next to the tomatoes.  For here yet another American champion with a photogenic quality and a fan club is chomping through promise of  the morrow's Russian dill pickles.  And so the charismatic black swallow-tail causes consternation when I gently point out the potential loss of beauty as the pink army of the kitchen methodically removes and destroys the black swallowtails, Papilio polyxenes  that are devouring the one meter square patch of dill.  The ferocious American insect onslaught is match by the focused determination of Russia to have a harvest, and if I want to eat, my thoughts are best expressed to the mocking bird above.

In a garden patch of several square meters, the world of invasive species problems is lit by the harsh light of the infinite choices of complex systems with all the human values and physical complexities easily seen.   Invasive species in a general sense are species that, due to human actions, disturb a complex adaptive biological system, causing a turbulence that can lead to unexpected outcomes or even the collapse of the system.  What belongs in a system is defined by humans; what is expected from the system is also defined by humans.  What seems like a strict scientific investigation is overlaid with human value judgments and therefore politics.  Even ideas of native take on a fuzzy vagueness that is based upon expected or desired outcomes.  Should native caterpillars be eating Asian dill planted by legal alien Europeans or naturalized Americans?  Is there any sense to the question at all?  Are there any truly “natural” areas left or has the fragmentation of the landscape in the lower 48 states left behind a mosaic of novel ecosystems that need to be managed (even if the management decision is to leave them alone)?

In the world of invasive species all of us are stakeholders and all of us have a duty to be part of the conversation bringing the “rightness” of our positions to the debate. In the end science cannot provide policy and value answers but rather it can give us the tools for identifying the limits of our knowledge.  It is up to each of us to address the value system that best supports the world we want to live in and how much we want our children to pay for our actions and our dreams.