Making Peace with Plants
Making Peace with Plants
Written onOctober 25 , 2012
I spent a recent morning clearing “alien” species out of one of my garden beds. By “alien” I don’t mean “non-native”; I just mean plants that I didn’t want in there, which is often what the word alien connotes: beings that don’t belong where they are. I wanted an artistic arrangement of red and green shiso in that bed (shiso is a Japanese culinary herb—or weed, or medicinal plant, depending on your point of view—that grows wild in many parts of Asia).
I made space for the shiso, I pulled up jewelweed, feverfew, prunella, goldenrod, gill-over-the-ground, Johnny jump-ups, calendula, clover, chickweed, various grasses (creeping sneakily in from the border of the garden), and probably a few others whose names I don’t know. Many of these have medicinal uses, or are pretty, or both, but I didn’t want them in that bed, so at that moment, they were aliens to me.
But sometimes I see these species differently. That morning, I carefully relocated the goldenrod to my orchard because organic apple guru Michael Phillips says that goldenrod is a beneficial understory species for orchards. I like it because its flowers attract a wide range of pollinators and beneficial predator insects. And it’s a good thing I like it because it’s everywhere in my backyard. It took over the edges of my pond, crowding out the various daylilies I had planted there; a huge clump sprang up in the middle of my raspberry patch, shading out the raspberries; and it seems everywhere I turn a new patch is growing with abandon. It’s one of those plants that is very good at colonizing any open available spot. And yet, I never hear anyone speak of goldenrod as invasive, despite its apparently “aggressive” behavior.
And grass! Whose idea was the lawn anyway? Among the weeds in my garden, grasses with long white rhizomes are among the most pernicious—leave any little bit of rhizome behind and grass pops up again, threatening to crowd out the plants I want. I would call that “invasive.”
So who gets to decide what’s invasive anyway? In this country we have a government agency, the National Invasive Species Council (NISC), that defines an invasive plant as one that is not native, and that causes some kind of harm—ecological or economic, or both. If it doesn’t cause harm, it’s not considered “invasive” (by this definition, I would say lawn grasses fit the bill—think of the harm caused by all those lawn chemicals getting into our waterways…) and if it is native, it’s not considered “invasive,” although many native plants will happily invade if given the opportunity—witness my goldenrod. NISC definition aside, many people think of “non-native invasives” as aggressive intruders that cause the extinction of native species and disrupt ecosystems; oftentimes any “non-native” plant is thought to have those characteristics.
The furor over alien invasives is intense. A neighbor recently told me she’s prone to stopping her car on the highway in order to jump out and cut off the seed heads of purple loosestrife. Someone else recently noticed the goutweed in my yard and said, “I see goutweed is your nemesis.” “Not really,” I replied. “I’m trying to make peace with it.” The conversation didn’t go much further. People seem disinclined to engage for long with those who raise questions around the way “invasive” is defined, the actual harm caused by invasives, and the tactics deployed to respond to the presence of these plants.
But I have had questions about these and many other aspects of this subject since I first learned about invasive plants, some 15 years ago. I had returned to graduate school in environmental studies after many years focused on other issues, including anti-immigrant sentiment and the politics of the “English-only” movement. My first concern had to do with the idea of “native.” To me, the rhetoric deployed around non-native species seemed way too similar to arguments concerning the dangers of immigration—including the idea that immigrants to our country would “take over” jobs, reproduce rapidly, and disrupt the healthy functioning of our communities with their different languages and culture. Of course I realized that such analogies were only that, and that the science of conservation biology was focused on the actual impact of introduced species on ecosystems, not on fear-mongering and bigotry. Or so I hoped. And yet, I did wonder if fear of difference or of change was playing a role in deciding both what a native species is and how we feel about them.After all, ecosystems are constantly changing, and plants have been migrating since they first evolved and began colonizing the primordial ooze.
According to the Natural Resources Conservation Service, native means “a plant that is a part of the balance of nature that has developed over hundreds or thousands of years in a particular region or ecosystem.” “Hundreds or thousands of years” is further described as plants that were here when Europeans first arrived. This makes some sense, since European colonization of this continent initiated much more rapid movement of species across greater distances than ever before. But under this definition, a huge number of plants now common (and often beloved) in New England are non-native. For example, daylilies (native to Asia); lilacs (native to Eastern Europe, introduced sometime after 1600); earthworms (most of our local earthworms arrived with the first European colonists); lawn grass (Kentucky bluegrass, for example, introduced from Europe); and apple trees (only crab apples were here when the colonists arrived—the center of origin for apples is central Asia). Oh, and honeybees, too, and just about everything we grow in our flower and vegetable gardens. Rhubarb? Comfrey? Not native. Tomatoes? Definitely not native despite that “native tomato” label you might find at the store. Corn? Actually corn was here at the time the Europeans arrived. It was first domesticated in southern Mexico, but it had migrated north, with the help of indigenous peoples and reached what is now Vermont by approximately 1100. Come July it certainly appears invasive, since monocultures of it cover large swaths of our farmland. But it turns out the NISC has this additional clause in its definition: “Invasive species are not those that humans depend upon for economic security, maintaining a desirable quality of life, or survival.” So, if we want a species in our neighborhoods, or on our farms, because it improves our quality of life, it’s not invasive. That explains the corn and the lawn grass….
Those who are most concerned about the presence of alien invasive species emphasize that these are species that were introduced by humans and that cause some kind of harm. But how do we decide what is harmful? Earthworms, here in the Northeast, are usually considered highly beneficial. At least we gardeners consider them beneficial, since they produce enriched soil conducive to growing our many non-native crops. But earthworms in forests consume the “duff” layer on the forest floor, and that may be harmful in the long run for some of our iconic tree species such as the sugar maple that rely on the nutrients in that duff. What to do?
Clearly it would not make sense to try to eradicate earthworms—there are far too many of them and they indeed do a lot of good. But if the science were very clear that earthworms were radically altering the ecology of our forests and harming maples, it might make sense to try to keep people from bringing earthworms into forests. Unfortunately, the science is rarely “very clear.” Ecology is complex, and it’s not easy to tease apart what exactly has caused changes in population demographics in a given ecosystem. When an introduced species becomes dominant, is it the new plant’s behavior that is causing the problem or some change in the system that happened before the new plant arrived? And how do we balance what we might perceive as “harm” in a given moment, with the benefits some of these species bring, not only to us, but to the wildlife that feed on their seeds or gain a new source of pollen? And since climate change is likely to bring a huge number of unfamiliar species our way in coming years, are we to put up barricades to keep them out?
Some voices have questioned some commonly held views about natives, aliens, and invasives. In his 2003 book Invasion Biology: Critique of a Pseudoscience, David Theodoropoulos suggests that the rapid dominance of one species often occurs due to events prior to its arrival, such as fire or other disruption—often human caused—or the cessation of indigenous land management practices. He also questions the idea that introduced species often cause the extinction of native species, citing numerous studies suggesting otherwise. In 2009, biologist Mark Davis published his book Invasion Biology, in which he argues that “alien” and “native” invasive species display exactly the same behaviors and that most “non-natives” are not harmful. In 2010, herbalist Tim Scott published Invasive Plant Medicine: The Ecological Benefits and Healing Abilities of Invasives in which he suggests that invasive plants may be serving an ecological function, protecting disturbed land until other species can repopulate it. He also describes the many medicinal and culinary uses of some of these species.
None of these writers are saying that invasion is inherently a good thing, but all of them emphasize that it is human behavior—the disruption of ecosystems (through building, mining, logging, and paving over the landscape) and global travel and commerce (through which we move countless species to places they would never arrive otherwise)—that most likely triggers invasions. They encourage us to shift our emphasis from militaristic crusades to eradicate invaders toward a more thoughtful effort to change our own invasion-causing behaviors, make peace with many of the invasive plants in our environment (using these abundant plants for food and medicine is one approach) and, in those cases where there is clear evidence of harm, choose the least damaging method of reducing that potential harm.
When I see one species dominating a landscape, I become as anxious as the next person. I recognize that some species do cause the decline of other species, or carry with them serious diseases that could, for example, radically transform the configuration of our forests. But, except in cases where there is danger of widespread disease or other serious ecological damage, and the numbers of an introduced species are still very small, it seems both arrogant and unwise to attempt the complete eradication of any species from a certain place. Once a species is eradicated, there is no possibility that other species might adapt to it or evolve so as to render the invasive species less problematic. Chances are good that over time, the problematic species will return in high numbers yet again.
And removal of a dominant species—which, unless replanted with other species, leaves bare ground and empty niches behind—is likely to have its own ecological consequences. Wouldn’t we be better off trying to work with nature to restore more diverse habitats in regions where these plants have become dominant? Wouldn’t it be better if we tried to prevent habitat disruption in the first place? I don’t claim expertise in invasion science, but I would want to look at all the evidence before I accepted that an eradication program was the best approach. Reducing the numbers of an invasive species (short of complete eradication) may be warranted at times, but that must be balanced against the harm that could be caused by the methods used.
A recent survey of those who are experts—for example, scientists whose main focus is the study of invasive species—found that habitat loss and degradation, human population growth, and global climate change were rated as greater threats to biodiversity than alien species, with over-hunting and commercial exploitation of species coming in fifth. Forty-one percent of the respondents agreed that the ambiguities of the science are often glossed over in order to sound the alarm of a crisis. Sixty-five percent agreed that “there should be less emotional xenophobia regarding invasive species.”
I’m not certain whether the division of species into “native” and “non-native” is helpful, but I’m pretty sure that describing specific plants as “evil,” “aggressive,” “intruders,” or “enemies” is not. Even if people don’t intend it, this language reinforces the idea that “foreignness” is dangerous and suspect. Why not focus instead on evidence of harm in specific cases of introduced species and, in the absence of such evidence, consider the possibility that we humans have much to learn from nature, not least that defining what is “native“ may be more a matter of our own prejudices and anxieties than of nature’s design. And that “balance” in nature is precarious at best.