Researching unfamiliar plants and invertebrate species* I see on my walks with Dash, I’ve come to recognize there are a large number of flora and fauna immigrants along the trail. Many of these world travelers were assisted or even abducted by people who wanted to have something for the garden that reminded them of their homeland, or they had a taste for the rare and exotic (at least rare and exotic for North America), some were hitchhikers. No matter how many generations of kin have lived here, no matter that an individual plant or animal was bred and born/hatched/germinated here, humans do not offer introduced non-human species the chance to become a naturalized citizen.
When an introduced species is able to not just survive in its new environment with little or no assistance from humans, but thrive, competing with the natives for niches, causing damage to the environment, or the human economy, or human health… then we reclassify it as an invasive, placing the blame on the uppity immigrant and, for the most part, forgetting that we sponsored their passage to a new world.
For example, English ivy (Hedera helix)… which evokes pastoral villages and thatch-roof cottages as it curls up like a contented cat in the shade beneath trees and climbs up brick walls, over fences, through garden gates, and out into the wider world looking for adventure.
Or golden-and-silver honeysuckle (Lonicera japonica). This Asian native is a twining vine with sweet-smelling flowers introduced as a ground cover. It can claim new territory through seeds and through shoots, and in doing so has become common enough to be adopted as a food source by deer, rabbits, hummingbirds, and other wildlife. As a kid, my friends and I learned how to harvest honeysuckle nectar, a skill I’m happy to share with Sidewalk Zendo readers through the magic of the Interwebs.
The most easily identifiable immigrant tree on the Huckleberry Trail, at least when it’s blooming, is the Tree of Heaven (Ailanthus altissima), brought to the US from China and Europe in 1784 and initially considered by gardener-collectors as quite the catch. However, it has subsequently earned the monikers “stink tree” and “tree of hell” because: 1) the flowers have a strong, unpleasant scent — I think it smells like the garden cat referenced above has been spraying the landscape with super-concentrated urine; and 2) because it can reproduce via root “suckers” as well as by seed and is, therefore, very difficult to eradicate.
Burning bush (Euonymus alatus) is a deciduous shrub native to central and northern China, Japan, and Korea. Popular as an ornamental plant for it’s bright red autumn leaves and fruit, it has spread into eastern North American woodlands, causing some states to prohibit importation and sale.
I pass by a group of 8-10 common lilacs (Syringa vulgaris) along the trail, planted in a straight line to fill a gap in the woods. In spring, when these shrubby trees are in bloom, I’m reminded of the lilac bush near the front door of my childhood home. Mom would help me cut a few fragrant bloom clusters (which always look like a popsicle to me), wrap the ends with wet paper towels, then swaddle the stems in aluminum foil like a burrito so I could take them to school as a gift for my teacher.
One plant I immediately recognized as a non-native from my very first walk on the Huckleberry was bamboo. There’s a small grove between the trail and a house, possibly planted as a privacy hedge of sorts. When there’s a strong breeze I can hear the hollow stems bumping into one another, sounding for all the world like wind chimes. This trait has endeared the plants to me, even though I know bamboo can be environmentally problematic on this continent.
I’ve discovered some immigrant wildflowers along the trail as well, including the spotted knapweed (Centaurea maculosa), originally from eastern Europe and now widespread across North America. It has a number of survival advantages over its native neighbors, including: 1) a sturdy taproot that sucks up water faster than its native neighbors; 2) a root toxin that stunts the growth of other plants; 3) the ability to spread quickly due to high seed production; and 4) it isn’t popular with wild herbivores so it doesn’t have to contend with grazing pressure (although domesticated sheep will eat it). Even knowing all of that, I have to admit I still think it’s pretty.
Another pretty problem is the purple loosestrife (Lythrum salicaria). It looks quite similar to native plants like fireweed (Chamerion angustifolium) Liatris (Liatris spp.), and spiraea (Spiraea douglasii) but it’s originally from Europe, Asia, northwest Africa, and southeastern Australia. It likes (as one of my college professors used to say) to have wet feet, preferring to put down roots in ditches, damp meadows, marshes, and alongside ponds and lakes. It has been known to crowd out cattails (Typha spp.) and disrupt water flow in rivers and streams.
Plants aren’t the only immigrants living along the Huckleberry. There are insects, too, including the cabbage white butterfly, above (Pieris rapae), which was accidentally introduced to North America, Australia, and New Zealand, and the European gypsy moth, below (Lymantria dispar), which is destructive to hardwood trees in the eastern U.S.
Another invertebrate immigrant that’s concerning for North American native trees, is the emerald ash borer (Agrilus planipennis). It was inadvertently brought to the U.S. and Canada in 1990, probably in packing crates. In its native northeastern Asia range it has low population densities and doesn’t cause significant damage; however, it has spread quickly on this continent in the absence of resistant trees, predators, and parasitoid wasps.
There are also vertebrate immigrants in southwestern Virginia, of course, although some of them are so well-entrenched and familiar we may not think of them as foreigners any longer. The house mouse (Mus musculus) is originally from Asia but it spread to the eastern Mediterranean in around 13,000 BC, then into the rest of Europe about 12,000 years later as human agrarian settlements reached the size needed for house mice to move in. They are now about as ubiquitous on Planet Earth as Homo sapiens.
The house sparrow (Passer domesticus) was brought to Brooklyn, New York, in 1851, as the first of many introductions attempting to control an insect infestation. By 1900, it had spread west as far as the Rocky Mountains. In the 1870s, house sparrows were introduced in San Francisco and Salt Lake City, aiding their western expansion. The species is now regarded as a pest and a threat to native birds by many. One problem with this hypothesis is that humans have changed the habitat so significantly that even if we were to eliminate every single house sparrow on the continent, the native birds that have disappeared from our urbanized landscapes won’t return; they would no longer recognize these spaces as home.
The common starling (Sturnus vulgaris) has the unique distinction of getting a lift to North America due to some name-dropping by William Shakespeare. In the late 1800s, the American Acclimatization Society set a goal of bringing every bird species mentioned in the works of The Bard to North America. They released about 60 starlings into New York City’s Central Park in 1890, and now there are approximately 150 million starlings occupying southern Canada and Alaska south to Central America. Starlings are considered a pest specie sby the US Department of Agriculture, even while though the agency admits this species consumes an enormous number of crop-damaging insects.
Oh, by the by… it may surprise you to learn that the earthworm that immigrant starling in the photo above is eating is an immigrant, too. Of the 182 earthworm taxa presently found in the U.S. and Canada, 60 are introduce species, primarily from Europe and Asia.
I’ve always found it odd that humans are quick to classify other species as invasive, accidental, or introduced when they expand their range, but never apply the same categories to ourselves, even though we have spread out from our original home in Africa to cover the globe like swarm of fire ants.
Using the definition humans apply to wildlife, Dash and I are immigrants here, too, despite the fact we were both born in North America. His breed hails from England, though he was born in Texas. I was born in Missouri, and the path from there to my current home in Virginia has been… circuitous, shall we say. Moreover, I’m a certified mutt, with a much less impressive pedigree than my wirey walking partner, and no Native American DNA in my gene pool — I’m Scottish, English, German, and Swiss.
Clearly, Dash and I both qualify as introduced. I hope we’re not invasive… but that’s really not for me to say.
Who are the flora and fauna immigrants living in your neighborhood? Share your thoughts, experiences, and photos in the comments section below!
*Since I’m a wildlife biologist I usually recognize most vertebrate wildlife living here.
[Thanks to the following photographers for making their work available through the Creative Commons license: David Strom, Foxspain Fotografía, Janet Tarbox, Roberto Verzo, Katja Schulz, Pearl Pirie, 55Laney69, jocelyndale, Manjith Kainickara, Ettore Balocchi, USDA, Bryant Olsen, Eric Bégin, and hedera.baltica. © 2017 Sidewalk Zendo. Reprints welcomed with written permission from the author.]