Gardening Invasive Species

Reconsidering Invasive Species: Living in the Wrong Place at the Wrong Time

A photo of Japanese Knotwood in seed by Vincent Frano

 Japanese Knotweed in seed. Photo credit: Vincent Frano

Many of us love a good villain. There’s something cathartic about directing one’s fear, anger, and morbid curiosity at a clear “bad guy,” someone who deserves the negativity we feel towards them. In the black and white world of good vs. bad the heroes and villains are easy to identify and respond to, giving us a sense of instant satisfaction. Since the term “invasive species” was first brought into the public consciousness by Charles Elton in 1958 — in his book The Ecology of Invasion by Animals and Plants — there has been a trend of grouping species into “heroes” and “villains” based on their origins. Native species have become the heroes, the ones to protect and support, while species from distant regions are quick to be labeled the villains to be reviled and destroyed. This is certainly a simple, straightforward way of approaching the movement and interaction of species in a globalized world; it fits neatly into human cultural ideals that prefer such dichotomous thought. However, this dichotomy lacks the nuance and fine detail present in the natural world (which is the world itself) and may actually hinder critical thought and scientific advancements in ecology and conservation. Here I’d like to consider the many sides of the story, inviting in the murky, grey areas so we can begin to approach invasive species with curiosity and open minds.

Damaged Ecosystems

There is no doubt that species introduced to a novel environment can profoundly impact the ecosystems they enter. I witnessed this to a startling degree while studying in New Zealand for an intensive on ecosystem restoration, indigenous land management, and invasion biology. New Zealand, being a small island nation, has suffered immensely from the impacts of invasive species. The worst offenders are possums (Trichosurus vulpecula), introduced from neighboring Australia; a myriad of European species, including hedgehogs, rats, and weasels; and various plants, including kikuyu grass (Pennisetum clandestinum). Some of these species, like Norway rats (Rattus norvegicus), were introduced accidentally, while others, like kikuyu grass, were introduced intentionally for agricultural and industrial purposes (kikuyu grass was planted for pasture and erosion control). During my studies on the North Island I traveled from Auckland up to the area around Motatau, stopping along the way to visit conservation projects, Maori land stewards, and protected islands. Even in the remote areas around Motatau, where you can see the Milky Way streaked with purple and blue light on clear nights, I was struck by the lack of birdsong.

A photo of a hedgehog on pine needles and pieces of wood near Montau in New Zealand by Vincent Frano

Hedgehog spotted on a logging road near Motatau - Hedgehogs, introduced to NZ from Europe, are a major threat to kiwis, often destroying nests and eating eggs. Photo credit: Vincent Frano

New Zealand is home to many magnificent and unique species of birds, the most famous being the kiwi (Apteryx spp.). Many of them, kiwis included, have been under immense pressure from introduced species, particularly those introduced by European colonists and their descendants. While staying with a Maori family at their remote homestead, my hosts explained how the forests on their family’s land were once filled with birdsong. Stories shared from their elder family members spoke of the beautiful symphony that could be heard every day in the temperate rainforests and the certainty of hearing the kiwi’s mating call on winter evenings. Today, while the kiwi’s call can still be heard on occasion, the symphony of birds has become a memory. In particular, possums, weasels, hedgehogs, and cats have decimated the island’s population of endemic and native birds. This foreces many avian conservation efforts to move to small, coastal islands where invasive species can be excluded and managed more easily. These island sanctuaries allow visitors to hear the cacophony of birdsongs that once filled the North Island of New Zealand.

A photo of a purple and pink sunset over silhouetted hills and trees near Montau, New Zealand by Vincent Frano

Sunset near Motatau - With luck you can hear the kiwi bird’s mating calls on calm Fall and Winter nights. Photo credit: Vincent Frano

Throughout the world there are similar stories of introduced species causing immense and at times irreparable harm to native ecosystems. Predatory animals and dense, fast growing plants — like the species introduced to New Zealand — tend to be the most damaging when introduced to a new region. While we cannot ignore these facts, it is important to consider that what is deemed invasive can be a reflection of the times and what is considered culturally or socially important. In North America, many of us now consider turf grass, earthworms, and honeybees to be a natural part of our gardens. Rarely do we consider that all three of these species (or groups of species, as with earthworms and turf grass) were in fact introduced from other parts of the world.

Before They Were Accepted

A photo of two cows grazing on short grass in the sun by Vincent Frano

Turf grasses were introduced to North America from Europe by colonists for livestock. Photo credit: Vincent Frano

Today honey bees (Apis mellifera) and earthworms (ie. Lumbricus spp., etc.) are particularly lauded as beneficial to the environment, but this wasn’t always the case (and still may not be). When European colonizers first settled in North America they brought plants and animals intentionally for agriculture and unintentionally in ship ballast and cargo. Earthworms arrived, likely unintentionally, and quickly began to transform the landscape by devouring leaf litter and decaying materials. The rapid turnover of decaying matter led to a change in soil composition, increased forest soil erosion, and likely the reduction of native organisms adapted to a worm-free ecosystem. In addition to worms, colonists brought honey bees which indigenous peoples dubbed “white man’s flies” because the bees signaled where colonists had settled. Finally, turf grass (ie. Poa pratensis, etc.) was introduced by colonists to replace native prairie and bunching grasses which they deemed poor feed for their livestock and to recreate the lawn-like environments they were familiar with in England and Northern Europe. Together, along with many other plants and animals introduced by colonists, these species helped transform North America into the ecosystems we are familiar with today. Indeed, the North America known to pre-Columbian indigenous peoples would seem foreign to those of us who live here today. We now coexist with numerous species from Europe, Asia, and Africa, many of which are not considered invasive even though they are not native.

Double Standard

A map of the United States of America showing the surface areas of turf grass in 2005. Areas with a higher percentage of turf grass are shown in darker shades of green and seem to be concentrated in areas with the biggest population density.Map showing turf grass surface area in the USA from 2005. Map credit: Cristina Milesi, NASA Ames Research Center

In the United States, turf grass covers approximately 2% of the total land (based on a 2005 NASA study). Although turf grass excludes native plant species, fragments habitat, and reduces native species biodiversity where it is dominant in the landscape, this group of species is not considered invasive. Aside from numerous articles describing how to ditch your lawn for easy to care for regionally native plants, you’d be hard pressed to find a campaign against invasive turf grass that resembles those against japanese knotweed or garlic mustard. For species labeled invasive, there is often an aggressive and pesticide heavy management plan with a goal of total (or near total) eradication. So why do we tolerate introduced turf grass when it occupies 40 million acres of land in the US, far more than the land occupied by our biggest crops like wheat and cotton?

Similarly, honey bees are considered to be an important insect and have become the poster child of many conservation efforts. The call to “Save the Bees” has tended to focus on honey bees, leading people to consider bee keeping and helping honey bees to be beneficial to the local environment. Unfortunately this is far from the case. Honey bees are incredibly abundant worldwide. Thanks to humans who keep them for honey and their pollination services for agricultural crops, there are an estimated 1 billion honey bees in the US and Canada alone!  The bees whose populations are declining are native bees. Native bees have received far less public attention and are not well understood or recognized by the general population. Furthermore, high densities of honey bee populations have been associated with increased competition with native bees, resulting in a decline (PDF) in native species. If honey bees are out-competing native bees – whose populations are struggling – then why do we tolerate them?

Left: A photo of a native bumblebee on a white Queen Anne’s lace flower with an out of focus background by Vincent Frano. Right: A photo of a European honeybee drinking from yellow goldenrod flowers by Vincent Frano
Left: Native Bumblebee on an introduced Queen Anne’s Lace flower.
Right: Introduced Honey Bee on a native Goldenrod flower (both taken in Massachusetts, USA) Photo credit: Vincent Frano
Money seems to be the short answer to the question of why some introduced species are labeled invasive and others are not. In North America, invasive species cost an estimated $26 billion per year. This cost comes not only from management and removal but from losses to industries such as agriculture, commercial fishing, and infrastructure. While there is certainly an ecological impact, much of the “fight against invasive species” is driven by economics and industry. The introduced species that cause the greatest amount of economic damage get the most attention as something to be removed, while those that benefit the economy — like turf grass and honey bees — are given a pass. From this viewpoint, ecological impacts, no matter how great they may be, do not carry as much weight as economic ones. 

The Human Impact

A photo of the results of logging in New Zealand. In the foreground and on the right are cleared areas with no trees and a view of the faraway mountains. On the left there are still some European pine trees standing.
Logging in New Zealand - these mountainsides have been planted with a single species of European pine for lumber. The trees are harvested by clear cutting and later replanting. The forest pictured is in the process of being converted back to native forest by the landowner.
Invasive species are often blamed for biodiversity loss and extinction, but this is an oversimplification of the issue. As we’ve seen in the example of New Zealand, introduced species can deplete native populations and endanger their survival. However, not all introduced species cause the same level of damage, and it’s important to consider other factors that harm ecosystems and native species. Human activity (beyond helping other species to move) is a major contributor to ecosystem degradation, loss of biodiversity, and even extinction. When humans transform landscapes for their own purposes – such as building roads or farming and ranching – they inevitably alter existing ecosystems and impact the plants and animals that live there. Sometimes small populations of endemic species are displaced or destroyed. Most often, populations of plants or animals become isolated due to habitat fragmentation and loss of migration corridors, which leads to reduced genetic diversity and poor health. In fact, roads and turf grass are major contributors to habitat loss and fragmentation. For example, a study in Massachusetts (video) found that up to 64% of wetland habitat loss is due to agricultural conversion, road building, and construction alone.


Moving in a Changing World

The conversation around invasive species becomes even more nuanced when we take climate change into consideration. With temperatures changing across the globe, species have begun to move to areas with more favorable conditions. As temperatures rise in one region, species migrate from their historic regions to ones with more favorable conditions in the present. Armadillos, maple trees, moose, marine snails, and many other species have been documented in regions outside of their historic range. Some conservationists and local governments have labeled these migrants as “invasive”, calling for their removal. Yet many scientists are now calling for a reconsideration of how we approach introduced species, rethinking the “invasive” and “native” dichotomy. In a rapidly changing world, our ideas of conservation need to adapt and evolve. Does it benefit ecosystem health and biodiversity to eradicate novel species or prevent their migration if that species can no longer survive in their historic range? 


Critiquing the System

Left: a photo of a native female woodcock bird nesting among fallen leaves and the stalks of introduced Japanese knotweed by Vincent Frano Right: a photo of the same woodcock nest in fallen leaves and knotweed stalks without the bird by Vincent Frano. You can see three small cream colored speckled eggs.
A native female Woodcock nesting in introduced Japanese Knotweed in Massachusetts, USA. Photo credit: Vincent Frano
Today many scientists are rethinking invasion biology and how to approach introduced species. The “non-native = bad” method fails to take into account the complexity of the issue. In addition to species moving themselves, we need to consider how introduced species interact with other species in their new environment. Indeed, there are many introduced species that have been living in their “new” region for a century or more. Some of these species are showing signs of integrating into their current environment, sometimes with beneficial effects. In my own anecdotal observations, I have witnessed uncommon native species, like Bloodroot (Sanguinaria canadensis) and Woodcocks (Scolopax minor) utilizing habitat created by the introduced Japanese Knotweed (Fallopia japonica). Additionally, the plant’s flowers provide a late-season nectar source for native and non-native pollinators. Beyond this, scientists have observed introduced grasses and trees in California providing habitat for native and threatened species. There is also some evidence that introduced species may begin to speciate, developing into a unique species adapted to their current environment and losing their ability to cross or mate with their ancestral species. These factors introduce a significant amount of “grey area” to the conventionally black and white approach to invasive species, forcing us to look more carefully at the issue.
There is also the fact that many native species can be equally aggressive in the environment. One example is the Mountain Pine Beetle (Dendroctonus ponderosae), a North American native that is responsible for killing the most native trees in the US compared to all other tree damaging insects. The economic impacts of the damages caused by this native species negatively affect both recreation and the timber industry in North America. Similarly, wild grape vines (Vitis spp. - many native to North America) are implicated in damages and economic losses, particularly to the timber industry.
Seeing a species (native or otherwise) causing damage to other species can also be a source of anxiety or confusion to people. On one occasion I was assisting with the removal of Oriental Bittersweet (Celastrus orbiculatus) from a park in Western Massachusetts. In the same area there were multiple native grape vines growing over the trees along with the Oriental Bittersweet. While working, a visitor to the park stopped by our team and requested that we do something about the grape vines which were “tearing down all the trees." This visitor was clearly upset by the fact that the grape vines, as with many types of vines, can cause damage to trees by weighing them down. The overseeing park ranger politely explained that we were only removing non-native species and that the grapes are native and simply doing what they do in their ecosystems – growing over trees and sometimes weighing down branches or full trees. The resulting damage creates openings in the canopy that allow light to reach understory plants and saplings. The takeaway here is that destruction is a part of the native ecosystem and our response to this destruction is largely based on emotions or economic drivers.
Left: a photo of a forest of young, thin tree trunks with moss, and fallen leaves carpeting the ground by Vincent Frano. In the center is a tangle of dark, thick native grapevines Right: a photo of native jewelweed plants by Vincent Frano. The jewelweed has bright green leaves and yellow flowers speckled with red, pink, and orange.
Left: Native grapevines in Massachusetts form dense tangles, climbing over trees in a race to reach the canopy, sometimes pulling down tree limbs and old trees in the process.
Right: Native Jewelweed, one of several native species with aggressive spreading habits, allowing them to form dense colonies. Photo credits: Vincent Frano
Native species can also outcompete other native species by forming dense colonies. These plants are often referred to as aggressive or as having an “invasive habit.” Jewelweed (Impatiens capensis) is one such native plant; its growth habits are so competitive it has even been shown to out-compete notorious introduced plants like Garlic Mustard (Alliaria petiolata). In its preferred environment, Jewelweed can form dense colonies that prevent the growth of other plants, including other native species. In my garden, pulling Jewelweed is a constant task since the plants have projectile seeds that shoot out in all directions when the seed pod is disturbed, allowing the plant to spread easily.
I have also witnessed large areas of wetlands carpeted with the native Arrow-leaved tearthumb (Persicaria sagittata). This species can form dense mats that are difficult to move through or manage thanks to the plant's numerous sharp barbs that scrape and tear at bare skin. While native, this plant certainly makes the areas it colonizes unpleasant for humans and it appears to form dense enough stands that other species seem to struggle with establishing in the same area. Given that native species can be just as troublesome or destructive as non-native species, how do we determine where the line is drawn?

Possible Approaches

Two photos of a meadow in Massachusetts with a mix of low and medium-height flowering plants including Goldenrod and Queen Anne’s lace by Vincent Frano
A meadow growing in my yard in Massachusetts features several native and non-native species growing together. Photo credit: Vincent Frano
In an interconnected world with complex issues, it can be difficult to know how to approach an issue as vast and fraught as invasive species. In my own opinion, the best approach is one that is open to adaptation as our collective knowledge of nature expands and evolves. I once approached all non-native species as “bad” and would do my best to eradicate them from my home and the parks I frequented. As my knowledge of ecosystems and approaches to land management grew, I began to shift my approach to one that was more open to the presence of non-native species in the landscapes I encountered. The ways each of us relate to and approach such complex issues will certainly vary, but the key is being open to changing one’s approach if the understanding of an issue shifts – essentially, letting go of the “my way or the highway” mentality that tends to keep our ideas or approaches stagnant, regardless of new information.

Keeping in mind that things may change, here is my approach to invasive species as I understand the issue today:
  • Avoid planting highly aggressive plants that are known to outcompete native plants or cause major disruptions in the landscape.
    These plants are typically listed as “invasive species” by the USDA and are extremely difficult or impossible to remove once established. These may include: Japanese Knotweed, Oriental Bittersweet, and Japanese Barberry. These plants generally have extensive root systems with deep tap roots that cannot be fully removed once the plant is established. They are also capable of generating roots from cut stems and sometimes leaves.

  • Manage aggressive plants (like the ones named above).
     Pulling young plants before they have a chance to establish. Leave pulled plants in a location where their roots will dry out and cannot make contact with the ground (such as hanging them in a tree’s branches). Cut back established plants that encroach on plants or landscapes you wish to maintain. But know that you will not be able to eradicate established colonies (even when using large machinery and glyphosate, there is no guarantee of eradication of species like Oriental Bittersweet, Japanese Knotweed, etc.) and focus your removal efforts on areas where aggressive species impact landscapes that are actively used or managed or where sensitive species are affected.

  • Don’t stress about non-native species in environments that are heavily impacted by certain human activities.
    This is where the nuances come in, so discretion and education around local landscapes and plants is beneficial. Abandoned lots, industrial yards, roadways, and so on are hotspots for many aggressive species that are considered invasive. However, these environments are often difficult for any plant to live in. The plants that thrive in these areas, which often have high levels of soil contaminants, are the ones adapted to the harshest environments – Japanese Knotweed, for example, is adapted to colonizing volcanic areas following an eruption. These aggressive plants, while not native, can stabilize soil and some even take up soil contaminants. While native plants can do this as well, non-native plants may be the only species present in an anthropogenic environment. Unless there’s a plan to replace every non-native with a native (ie. swap the knotweed for goldenrod), it’s ultimately counterintuitive to remove these plants from the landscape.

  • Consider the ecosystem you are planting in and whether the plants you’re choosing could pose a risk to the native ecosystem.
    If you want to grow a non-native plant, look for plants that a) are likely to die back annually in your growing zone b) are not prolific seed spreaders or highly attractive to seed spreading animals (ie. have many delicious fruits) c) do not spread by runners or suckers and d) do not easily propagate from root cuttings. The last one is really important, as these plants can regrow even from a very small portion of root or rhizome, making them difficult to remove once planted.

  • Plant aggressive spreaders in pots that are not allowed to make contact with the soil.
    These plants may spread by root division, sucker, or runner. Remember to cover the drainage hole so roots don’t escape into the soil.

  • Remove spent flowers of plants that produce a lot of seeds or fruits.
    This will prevent the plant from reproducing, but you can still enjoy the blooms.


Small Victories' Current Approach

A photo of a sunny meadow with a diverse mix of low and medium-height flowering plants by Vincent FranoA diverse meadow of native and non-native plants growing in New England. Photo credit: Vincent Frano

As the co-owner of a plantable stationery company that sells to a global market, the issue of invasive/non-native plants is high in my awareness. We occasionally receive inquiries about our cards and the seeds contained in them, typically regarding concerns over the plants being invasive. This is a matter we do take very seriously, but it’s one we also approach from a broad perspective that never settles on a single “right” or “wrong,” acknowledging that there is always room for change in an ever changing world. Our cards contain common garden plants across the globe.

While all native seeds would be great, here’s why our cards contain a mix of seed species:

  1. We sell globally and it is impossible to have seeds native to every region where we sell cards.
  2. Our paper makers are limited to what seeds are approved by the USDA and the Canadian and EU agricultural regulatory organizations. We have requested alternative seed mixes in the past, however, the seeds requested were not approved by these organizations despite being more broadly native to the Northern Hemisphere. Rest assured that the seeds in our cards are tested for purity and they are all non-GMO.
  3. Not all non-native species are “invasive.” If we planted only native plants, we wouldn’t have access to most fruits, vegetables, and garden plants we think of as important to our lives. This list includes: apples, roses, wheat, marigolds, and many more!
A photo of a Bower Studio seed card featuring an illustration of a Northern Saw-whet owl by Vincent Frano.
The cards in our Classics line have a mix of wildflower seeds embedded in them: Clarkia, Bird’s Eye, Black eyed Susan, Snapdragon, Catchfly, and Sweet Alyssum.

I acknowledge that this is far from perfect, and in an ideal world we would be able to offer cards with seeds specific to the regions where people want to send or buy cards. Perhaps one day we’ll get there, but for now this is what we’re able to do. Nevertheless, our cards primarily contain seeds of common garden plants, such as Snapdragon or Basil. While these may not be native to North America, they are ubiquitous in North American gardens and are not considered invasive, noxious, or particularly aggressive. Because of this, I do not believe that our cards are negatively impacting ecosystems any more than a well thought out organic home garden does. Of course, as I mentioned earlier, it’s important to use discretion when choosing what to plant in your region. So, if you are concerned about planting a particular seed (say, Sweet Alyssum), then it may be a good idea to purchase one of our Brights cards, which are printed on paper with a mixture of herb seeds. All of our cards can also be grown in a pot or planter, so there’s no worry about the plants escaping the garden.

A photo of a white, purple, and blue Bower Studio seed card with an illustration of a moon surrounded by diagrams of moon phases. The moon in the center has the text “wishing you many moons.”
The cards in our Brights line have a mix of herb seeds embedded in them: Basil, Chives, and Parsley.



The Takeaway

In the end, we are all living in an incredibly complex world that’s ever changing. We humans have certainly learned a lot about how the world we live in works, but we’re never going to have it all figured out. And even when we think we’ve got something figured out, there can be new information learned or different approaches that completely upend what we thought we knew. All this means that, in my opinion, we need to approach life with an open mind that’s curious and willing to adapt and shift over time.

I started this journey with invasive species nearly ten years ago and I have changed my views or adapted my approaches many times over. I began in that black and white world of all or nothing, ripping up every invasive plant I saw and battling them with a vengeance. As I immersed myself more in learning about plants, ecosystems, and human-ecosystem interactions I began to shift more into the “grey area.” Today I still manage non-native plants around my home, removing them as needed, but I’ve ended the all out war. On a planet that is suffering greatly from strictly human activities (ones that don’t involve other species) it feels counterproductive to wage war on the living things who are simply being themselves. Instead I think about the ways that we humans can work together to retell an old story: where humans are part of the ecosystem and we, like all living things, must exist in a balance. A balance that is ever shifting with time. Perhaps that’s all that “invasive species” are: a sign of a world off balance – and here we all are killing the messengers without really listening to what they have to say.

 

Other articles you may like: Invasive Plant Medicine, The Story Behind the Cards - Animal & Plant Companions

About the author: 

Vincent Frano is an avid student of nature. He is trained as an herbalist with over 10 years of experience in European traditions with knowledge of Ayurvedic and North American herbs. He holds a BS in Sustainable Horticulture from the University of Massachusetts, Amherst where he focused on herbal medicines, native plants, invasive species, and ecosystem restoration. Vincent is the co-founder of Small Victories and is the lead illustrator for Small Victories' products.

This article is copyright 2023 Small Victories.

All images are under copyright and may not be used without written permission from Small Victories.

More from: Gardening Invasive Species
Back to News

Explore more

Share this