Blue Ridge Naturalist: Ecologists Recognizing Value of Alien Plants

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Bees and other kinds of insects obtain nourishment from the blooms of Weigela, a spring-blooming shrub native to Asia. Photo: Marlene A. Condon.

Scientists are either waking up to what I’ve been saying for years, or finally becoming brave enough to speak out against the widespread invasive-plant movement. In an opinion piece signed by 19 ecologists in the journal Nature, they argue that “policy and management decisions must take into account the positive effects of many invaders.” (www.macalester.edu/~davis/Nature%20Essay.pdf).

Recognizing that “It is impractical to try to restore ecosystems to some ‘rightful’ historical state,” they go on to point out that eradicating or drastically reducing the abundance of invasive plants is “an impossible goal.” 

Critical thinking is a must for deciding invasive-plant policy to avoid harming wildlife and wasting millions in tax dollars. A situation in California illustrates the foolishness of blindly pushing an agenda without giving any thought to the real-world consequences of doing so.

In the name of “saving” the environment from so-called invasive plants, a movement has sprung up to remove Eucalypt (Eucalyptus globulus) trees from California. These trees, brought in from Australia, now serve as the most frequented overwintering sites for the western Monarch butterfly population. (milliontrees.me/2013/11/01/monarch-butterflies-in-california-need-eucalyptus-trees-for-their-winter-roost/)

Monarchs originally roosted in native conifer stands of Monterey Pine (Pinus radiata), Monterey Cypress (Cupressus maculatum) and Coast Redwood (Sequoia sempevirens). Sadly, extensive development, logging, and poor land-management decisions have reduced the number of these native-tree stands, leaving the butterflies to rely upon non-native Eucalypts.

Ignoring the fact that overwintering Monarchs are very much dependent upon isolated stands of these trees, government plans are mandating removal of them. Does this make environmental sense? Absolutely not; eradication of the Eucalypts means no wintering habitat for Monarchs, which means they will die. 

In other words, this deliberate destruction of habitat is taking place because of ideology, an illustration of the danger posed by people who have been led to believe they are part of an environmentally moral crusade. Native-plant folks out west have managed, as they have here in the East, to convince environmental organizations and government entities at every level that it is a moral imperative to remove plants deemed invasive.

But, the whole point of conservation of the environment is conservation of wildlife, without which the environment cannot function properly. Yet, absolutely no thought is given to how much so-called invasive plants support wildlife or serve important environmental functions in degraded areas. 

Thus, for example, in the city of Waynesboro, the Parks and Rec department decided it had to remove Japanese Knotweed (Fallopia japonica, formerly known as Polygonum cuspidatum) from growing along the South River greenway (Waynesboro News Virginian, March 9, 2018, “War on Weeds”). The main reason given for the removal of these plants was that they are preventing native plants from growing, but this statement is nothing more than invasive-plant folklore that gains credence by the act of repetition.

Read about virtually any “invasive” species and you will find that these plants are typically growing in disturbed areas where man or a weather event destroyed the original soil profile. As a result, the plants that had been growing there previously did not come back because they could not handle the altered physical conditions of the site. It’s why you see so-called invasive plants mainly along roadways, in parks, and along river trails—all areas easily seen by people who then mistakenly believe the exotic plants pushed out native species.

The newspaper stated that knotweed is a “formidable culprit to the river’s health,” but the true threat lies in its removal. This plant has superbly performed erosion control of soil in which native plants struggle to grow, feeds numerous kinds of pollinators when it blooms, and provides wonderful cover and nesting sites for numerous species of birds and the non-herbivorous insects that feed them. One need only to walk the trail with open eyes and an open mind to ascertain the truth of this statement.

Additionally, park employees would use herbicides to kill the knotweed. How can poisoning the Earth be less harmful than allowing alien plants to grow in areas where they are currently the most suited to thrive and thus provide badly needed habitat for wildlife? 

You might wonder how the invasive-plant movement became so entrenched in environmental and governmental circles. The answer lies in the treatment of it as a moral cause in which those who agree with removing “bad” plants are virtuous; those who disagree must be bad like the plants themselves. Under these circumstances, it is difficult for folks to take a stand in opposition; no one wants to be considered immoral.

However, this undertaking is deeply flawed. Rather than critically analyzing each situation and dealing with it in the most appropriate manner, plant nativists (people who practice a policy of favoring native plants over nonnative) take the approach that demands removal of every plant designated as “invasive,” no matter what function it is fulfilling in the local environment or how well it fills what would be an otherwise empty ecological niche.

Earlier this year, for example, someone removed a Leatherleaf Mahonia (Mahonia bealei) that was growing in a swath of red dirt along the road where I exercise. It was one of the few plants that had survived the highway department’s installation of a new guardrail. No native plants had been able to grow in the poor, dry soil exposed a few years earlier by construction, leaving an area several feet wide and long mostly devoid of plants to assist wildlife.

The Mahonia (a native of China) would have provided a very early source of nectar desperately needed by the first pollinators to become active in spring at a time when native plants in bloom are very few. Its fruits would later feed birds, such as Cedar Waxwings and American Robins. Now, not much exists in this area to feed either insects or birds, making the land a wasted resource.

Native or not, plants provide habitat, whereas bare ground does not. Nativists disregard the reality that native plants struggle to survive under the adverse conditions of road salt, mowing, drought, and disturbed, compacted and depleted soil. They would do better by the environment if, instead of pulling and pesticiding, they focused on eliminating the actual causes of alien-plant spread. 

Removing the Mahonia near the bridge resulted in no benefit to the environment, whereas it very much negatively impacted ease of survival for many insects and birds. And in California, removing Eucalypts may well doom the wintering Monarch butterfly population. 

4 COMMENTS

  1. As an advocate for the preservation of our urban forest in the San Francisco Bay Area, I am grateful to Marlene Condon for this spirited defense of introduced plants. Our urban forest is predominantly non-native because our pre-settlement landscape was treeless grassland. We need our trees for protection from the wind and our birds and the insects they eat also need the trees for habitat and winter nectar.
    Native plant advocates also eradicate many other useful introduced plants such as every berry-producing plant needed by birds. The berry-producing plants are sprayed with herbicide, which also harms the birds and insects that eat the berries.
    The native plant movement is damaging the environment and all its inhabitants, including wildlife. The “restoration” of native plants after eradication of non-native plants with herbicides is rarely successful, leaving us with barren landscapes. It is a cruel fiction that eradicating non-native plants and trees will benefit wildlife.
    Thanks to the Crozet Gazette for publishing Ms. Condon’s excellent article.

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