While researching the topic of invasive species we may be overcome with the overwhelming complexity of the topic. For the most part ‘invasions’ possess unpleasant overtones. Invasions are usually unwelcome, be they military incursions, or the arrival of objectionable biological eantities. Plants or animals not indigenous or native to our area could bring with them unwelcome environmental changes or damage. Included in the latter category are also pathogens such as bacteria, viruses, or fungi. Some invasive species apparently do not cause environmental damage. We perceive them, incorrectly, as native species. Such pathogens have arrived from afar, even from a foreign country. These undesirable arrivals may also be termed “exotic.”
Invasive species in the Americas are far more common than we realize. Research into species categorized as invasive reveals hundreds of organisms—plants, animals, and pathogens which were known not to be native to this hemisphere before the arrival of explorers from the old world. The New World, North and South America, would be virtually biologically unrecognizable were we to board a time machine and visit the Americas of Columbus’ time only 500-600 years distant, or Norse settlements about 500 years before that. Native American Indians inhabited a land biologically different in many ways. We recall the Native American experience on our continents hundreds of years ago with great fascination. The fascination is historical, political and biological.
We reference our personal experience in Northern New Jersey after the family moved from Central New York State in 1951. In 1904, the unique eastern American Chestnut forests became infected by a fungal disease which originated in East Africa—the “greatest ecological disaster in our forests.” After a half century the American Chestnut forests which frequently produced gigantic trees over 100 feet tall in Eastern US were nearly gone—three billion trees. Our home in New Jersey, built in 1926, retained much wood in its bookshelves and decorative wooden pillars. They were constructed from wood of the American chestnut.
Our family left behind a heritage of agricultural beauty on its way to Northern New Jersey. A mighty elm had overlooked our farm fields in Onondaga County, NY, where we harvested corn, wheat and oats. The majestic elm has since yielded to an invasive species—the dutch elm disease. In our current home in northwest Illinois, we contracted for removal of over a dozen “expired” elm trees—victims of the same dutch elm disease. As I write, another elm across the street from our home awaits its final demise. Elm bark beetles are the vector for spreading the fungus which kills many majestic elm species. Dutch elm disease appeared in the US in 1928. It was also an exotic ‘wilt’ fungus, an import from the Old World. Forty million elm trees have perished in the US—many more around the world.
Ash borer, an insect native to NE Asia whose larvae feed on the bark of ash trees, currently infests many of our local trees. It entered the ecosystem in 2002 in Detroit, MI, on wooden packing materials from China. The borer damages the tree’s ability to transport water. Dieback and bark splitting results.
Another personal experience with an invasive plant must be told, this time a harmless plant. In the last decade of my teaching career my students and I discovered a single, unusual woody plant in an unlikely forest location during a school sponsored trail hike. We returned to school with several huge leaves. One YouTube clip claims the leaves of paulownia tomentosa produced by the shoots of a tree cut down to ground level are as big as a car wheel. Pictures show gigantic leaves over two feet in diameter. The plant is known to consume enormous quantities of CO2. It is a prolific exotic from China which first arrived about 1840. Tongue in cheek, our students speculated the plant may have been a rare mutation from another planet.
More often than not, invasive species are deleterious. Most locales in our area are plagued with many invasive weeds and plants. Poison parsnip and garlic mustard are two common examples. There are many other illustrations.
The frequently quoted Genesis 1:28 contains an exhortation to ‘subdue’ the Earth. We carefully interpret the meaning of ‘subdue’ in the context of responsible environmental practice. Humanity has an obligation to study diverse characteristics of multiple species within their ecological niches. We must carefully avoid importing harmful invasive species, either deliberately or accidentally. Humanity’s record in this area has been deficient.
Our research of this topic from a personal perspective has inspired us to study the invasive species issue from a more global perspective.