In Defense of Nature

 

“Invasive” Plants: Friends or Foes? © Marlene A. Condon

M'm! M'm! Good! [Courtesy of the Campbell's Soup Company] Although the ancestors of the horse evolved in North America, today's domesticated animals enjoy eating the leaves and twigs of the alien Burning Bush (Euonymus alatus) from Asia.  

ALL TEXT AND PHOTOS © Marlene A. Condon

The popular environmental narrative blaming so-called invasive plants for the decline in insects and birds has brought about the destruction of much viable habitat in the name of “saving” our wildlife. But a failure of effectiveness has occurred: Removing “invasive” plants has not resulted in bringing an end to, or even a reduction of, the decline in insect and bird populations.

 Why the “Invasive-plant” Narrative Sky-rocketed So Quickly in Popularity 

In 2007, the book, Bringing Nature Home, was published by Timber Press. Written by entomologist Doug Tallamy, it quickly caught the attention of two large groups of people: native-plant societies with an avid interest in promoting the growing of native plants (especially “ephemerals”—those species that appear briefly in early spring), and birding organizations whose members enjoy seeking out numerous bird species.

When Dr. Tallamy posited that “[m]ost of our native plant-eaters are not able to eat alien plants” [page 7, Advanced Reading Copy, Bringing Nature Home] and that “aggressive plant species from other continents…were rapidly replacing what native plants [he had on his own property]” [page 11, Advanced Reading Copy, Bringing Nature Home], he spoke words native plant-loving people could rally around—and rally they did.

Native-plant societies exist across the land, and their members were ready and willing to talk to government officials, plant nurseries, and anyone who would listen to them about the necessity of ridding the environment of “invasive” plants and growing native species instead of alien ones. 

When Professor Tallamy pointed out that “Nearly all terrestrial birds rear their young on insects” [page 19, Advanced Reading Copy, Bringing Nature Home], he reeled in birders of every stripe—folks ready to flock to the aid of their beloved avian species by spreading the word that home landscapes should be filled with native plants to feed insects, that, in turn, would feed birds. 

Subliminal Inculcation 

Bringing Nature Home is written in such a way as to subliminally implant erroneous ideas into the reader’s head. For example, Chapter 5 is entitled, “Why Can’t Insects Eat Alien Plants?” [page 42, Advanced Reading Copy, Bringing Nature Home], the suggestion given that no insect can eat an alien plant, which isn’t true. Any butterfly enthusiast can tell you that Monarch Caterpillars are able to feed successfully upon many alien-milkweed species. 

Although this University of Delaware professor does insert the word “most” ahead of “native insects” by the second paragraph of the chapter, he goes on to list almost two dozen of “the worst offenders” (i.e., invasive plants that don’t feed herbivorous insects), many of which are, however, superb food sources for a large variety of wildlife, especially birds. 

This sapsucker returned repeatedly to the author’s Photinia shrubs to obtain sap that, in turn fed Gray Squirrels and a variety of songbird species.

Yet, birders and birding organizations, and land management agencies (local, state, and national parks, conservation and wildlife agencies, etc.) are working hard to rid the United States of these plants, all because an entomologist—who sees the natural world only through the lens of herbivorous insects and what they need—suggests “invasive” plants are useless to leaf-feeding insects that he sees as being of paramount importance. 

But the reality is that just because you get rid of plants seen as invasive, it doesn’t mean the area is automatically going to fill with native plants more palatable to phytophagous (plant-eating) insects. The unspoken premise is always that native plants will succeed in that location, but whether that happens depends upon the presence of native plants in the area as well as their ability to reproduce and survive in what may still be a degraded situation. It’s well known that areas filled with so-called invasive species typically contain nutrient-poor and compacted/rocky soils, conditions not conducive to the growth of most native plants. Additionally, in areas of deer overpopulations, you can rest assured that native plants will struggle to survive unless fenced off or caged. 

The Falsity of Invasive Plant “Facts”

Due to the falsity of the ideas constantly put forth about so-called invasive plants, folks have bought into the belief that these plants harm the environment. When erroneous ideas are repeated endlessly, they eventually are believed to be “true” by virtue of the repetition itself.

One such pervasive idea is that these alien plants push out native plants, but nothing could be further from the truth. When you clear an area of its topsoil and leave rock-hard subsoil exposed (conditions not suitable for most native plants), as is the case alongside roads when they are built and in areas where mining took place, you find that alien plants come into such areas and may well—over time—fill them. Years later, these locations may look to folks as if “invasive” plants displaced native ones, but that’s a misperception borne of ignorance and/or disregard of the site’s history. Even scientists fall prey to this misconstruction.

Professor Tallamy tells us in his book [page 11, Bringing Nature Home, Advanced Reading Copy] that when he and his wife bought 10 rural acres in an area “that had been farmed for centuries”, they got “anything but the slice of nature [they] were seeking”. He complains that at least 35 per cent of the vegetation on their property “consisted of aggressive plant species from other continents that were rapidly replacing what native plants [they] did have.” This quoted statement simply isn’t accurate. 

Farming degrades the land every bit as much as bulldozers and mining equipment. If cows/cattle roam the landscape, these beasts weighing a half-ton or more compact the soil. If the land is hayed, heavy machinery compresses the dirt and removal of the hay robs the soil of the organic matter required to rebuild soil tilth and regenerate nutrients. 

Anyone familiar with farms in the East knows that most of them today consist of terribly damaged soils as a result of centuries of farming. Thus Dr. Tallamy’s purchase in southeastern Pennsylvania displayed just what should be expected—nonnative plants filling in corrupted-soil areas where native plants simply had not been able to return once the land was left untended. Those alien plants were no more “aggressive” than colonizer native plants because they are, in fact, colonizers themselves, filling in what would otherwise be barren landscapes that wouldn’t support much wildlife. 

And the alien plants were most definitely not replacing native plants as this scientist stated. Physics tells us that no two physical objects can occupy the same space. That’s one reason you should believe the alien plants came into what had been an area mostly devoid of native plants. 

Indeed, I’ve witnessed this scenario repeatedly over the decades since I started paying attention to so-called invasive plants when I was a college student in the 1970s. In Virginia, I’ve documented Autumn Olive (Elaeagnus umbellata) alongside Virginia Redcedar (Juniperus virginiana) beginning to grow in deserted farm fields, with both (and sometimes, one or the other) finally filling the areas. Ironically, the species typically replaced over time were nonnative plants: Tall Fescue (Lolium arundinaceum) from Europe or Orchardgrass (Dactylis glomerata) from Eurasia and North Africa. 

Virginia Redcedar trees and Autumn Olive shrubs filling in a field that, decades prior, had fed cows in Albemarle County, Virginia.

The Problematic Anecdotes  

Bringing Nature Home is populated with anecdotes relaying the personal experiences of Doug Tallamy. His stories are often written so they plant false ideas into his readers’ minds, thus controlling them without their ever noticing. 

He tells us of encountering in his own yard “an excellent demonstration of just how restricted a specialist’s diet is”, where a specialist insect is defined as having “evolved in concert with no more than a few plant lineages.” [page 45, Bringing Nature Home, Advanced Reading Copy] He goes on to talk about a group of tent caterpillars that had stripped a small Black Cherry (Prunus serotina) of all its leaves. 

Dr. Tallamy writes, “What is interesting in this case is that there were still leaves available on the cherry” in the form of a Japanese Honeysuckle vine. “The caterpillars must have walked over the honeysuckle leaves repeatedly to find every last cherry leaf, and yet they had not taken a bite of the alien plant. Even as they ran out of food, the caterpillars simply did not recognize honeysuckle as a potential food source.” The subtle inference is that the caterpillars couldn’t eat the honeysuckle only because it was foreign, as if they would have recognized a native vine’s leaves as food. But those Eastern Tent Caterpillars couldn’t feed upon our native vines either. 

This tale serves to convince the uninitiated that alien plants are useless and shouldn’t be allowed to be here. But, while the caterpillars couldn’t eat the Japanese Honeysuckle, they could certainly have eaten Multiflora Rose leaves if Professor Tallamy had left these alien shrubs on his property (mentioned earlier in the book). As Dr. Tallamy points out, Eastern Tent Caterpillars (Malacosoma americanum) “are specialists on a single lineage of plants” in the Order Rosales; Multiflora Rose is in this very same Order. 

Omitted throughout his discussion is what the word “lineage”—a single line of genetic descent through time—represents: hundreds, if not thousands, of species. In other words, an insect is likely to be able to feed upon at least some of the plants that are related genetically, regardless of the country (geopolitical boundary) in which they originated, as you can see in the accompanying photos. A factuality is that you can find native insects feeding upon nonnative plants, but folks who choose to wear blinders can’t see what they refuse to look for. 

Native Eastern Tent Caterpillars feeding upon an alien Multiflora Rose shrub in Albemarle County, Virginia.

Close-up of a native Eastern Tent Caterpillar feeding upon an alien Multiflora Rose shrub in Albemarle County, Virginia. 

Value of “Invasive” Plants to the Environment

On list-serves, birders often lament the disappearance of birds from areas after mowing by highway departments or clearing by national or state park employees. These situations highlight a vital value of so-called invasive plants—that of providing habitat where there is likely to be none without them, often due to misguided beliefs about “neatness”. The reality is that removing alien plants removes habitat that is precious in a world with less and less of it. And it is not going to be replaced overnight. It takes time for plants to grow large enough to attract insects and to provide shelter for nests and/or from predators. In a world of disappearing organisms, removal of viable alien-plant habitat in the belief that “ideal” native-plant habitat would somehow be better simply adds to the difficulty these critters face for surviving another day. 

Dark-eyed Juncos (Junco hyemalis) and White-throated Sparrows (Zonotrichia albicollis) find winter sustenance along Japanese Stiltgrass (Microstegium vimineum)-lined roads, such as this one in Albemarle County, VA.

Another serious detriment for wildlife is the usage of herbicides to rid areas of “invasive” plants. These poisons, applied directly to animals, kill. They are not innocuous, though people treat them as if they are. Who examines plants carefully before covering them with herbicide? I can guarantee no one does. Yet if you look closely at plants of any sort, you will find organisms on them. 

The reason “Mother Nature” constantly works to fill areas with plants is so they can support wildlife; barren areas do not. Yet people often view areas of abundant plant growth as “weedy” if the plants are not the particular species they desire. They describe such plants as "aggressive”, “invaders”, “bullies”, or “weeds”, only because they want something different in their place. However, if you are trying to assist wildlife, you can’t garden or manage land as if it’s solely for your own appreciation. You need to evaluate it from the perspective of wildlife.

 A Variety of Factors Are More Relevant to the Disappearance of Insects and Birds than the Presence of Alien Plants in the Environment

Doug Tallamy insists a lack of native plants—or more accurately, trees—is the prime reason for the loss of insects and birds, but that’s nonsense. In the eastern half of the United States, plenty of native trees exist to feed the caterpillars that are really the sole focus of this lepidopterist’s concern.

Plenty of native trees exist in the eastern United States to support moth caterpillars, as can be seen here from a balloon over Charlottesville, Virginia.

More-significant causes of this dire situation are the abundance of lights burning (sometimes day and night) in developed and even rural areas.

This elementary school in Crozet, Virginia, could be planted with native trees and still not support caterpillars, thanks to the excessive night lighting that is a prime attractant to, and thus killer of, moths.

Lights attract moths, which then don’t reproduce, making for fewer and fewer caterpillars over time and therefore a lack of food for birds.

Moths, large and small, remain “glued” to a light in Shenandoah National Park, Virginia, at 7:30 AM DST.

And gardeners who worry more about their plants than wildlife spray or kill many insects, arachnids, and other kinds of organisms (such as slugs and snails) because they believe just about any critter on their plants poses a danger to their garden. Worse yet, extension agents across the U.S. reinforce public angst by providing much misinformation about so-called pests (e.g., sowbugs) that shouldn’t be seen in that light at all. Folks must learn to garden in a nature-friendly manner so gardening “pest problems” can be eliminated, thanks to maintaining the balance between plant-eaters and predators. [The Nature-friendly Garden, website: www.marlenecondon.com]

The “Invasive Plant” Narrative is Just Plain Wrong

Truth be told, an “invasive plant” can be defined as a plant that deer don’t eat, and/or a plant growing where someone prefers to see a different plant.

Deer overpopulations suppress many native plants, clearing the way for certain alien plants—or even certain other native species—to fill an area because they are left alone to reproduce. That’s natural succession; it’s not “invasion”. And the idea that plants must be native rather than alien, especially when alien plants can survive better than native plants in a particular area or due to climate change, is an arbitrary and capricious demand. If our wildlife doesn’t object to alien plants, then no reasonable grounds exist to insist upon supposed “habitat restoration”, especially where suitable habitat does not otherwise exist. A rare example of using common sense is the decision to leave alone nonnative Tamarisk shrubs for the Southwestern Willow flycatcher. https://www.nrcs.usda.gov/programs-initiatives/working-lands-for-wildlife/southwestern-willow-flycatcher

In a 1989 conversation with PBS journalist Bill Moyers, the novelist E. L. Doctorow said, “When ideas go unexamined and unchallenged for a long enough time, they become mythological and very, very powerful. They create conformity. They intimidate.” His words describe to a tee the current environmental narrative regarding so-called invasive plants.  Speak out and you feel the wrath of folks pushing their fictional environmental manifesto; indeed, I’ve lost jobs, thanks to such people.

The wholesale destruction of habitat currently taking place across this land adds insult to injury and must be stopped. If you truly care about saving our wildlife, don’t be intimidated by purveyors of “invasive”-plant mythology. Instead learn the facts and spread the truth. 

Autumn Olive shrubs—one of the most valuable wildlife plants one could hope for in areas with visibly degraded soil—were pesticided along a trail in Natural Bridge State Park, Virginia. State personnel were trying to follow the dictates of an erroneous and highly detrimental narrative: Rather than allowing the Autumn Olive shrubs to increase the diversity of plant life in an area hosting mainly Virginia Redcedar, which would increase the diversity of animal life, state personnel instead greatly limited how much wildlife the area could support.

NATURE ADVICE:

If people don’t begin to speak out against the “invasive-plant” narrative, wildlife will continue to lose habitat, leaving it with nowhere to go. Please, if you truly want to assist wildlife to survive, help stop this madness by taking time to observe alien plants and making note of the variety of wildlife you see making use of them. Then, spread the word!    

DISCLAIMER: 

Ads appearing at the end of e-mail blog-post notifications are posted by follow.it as recompense for granting free usage of their software at the author's blog site. The author of this blog has no say in what ads are posted and receives no monetary compensation other than the use of the software.