Invasive Species vs. The Global Economy

As humans have spread across the globe, other species have followed. The domestication of animals and the advent of agriculture helped speed up this process, but species have been traveling around with humans long before that. Presently, our ability to move species from one corner of the globe to another is unprecedented. As more countries join the global economy, the risk of outsider species establishing themselves in uncharted territory increases. Species introductions via globalization are not likely to decrease, and so the question must be asked: Are we, as a global community, equipped to address this?

A review published in Nature Communications in August 2016 warns that “most countries have limited capacity to act against invasions.” The authors come to this conclusion after analyzing available data about invasive species across the globe and developing a “global, spatial forecast for emerging invasions throughout the twenty-first century.” National responses to invasive species were assessed based on reports to the Convention on Biological Diversity (CBD).

As part of the 2011-2020 CBD Strategic Plan for Biodiversity, nations or states that are parties of the CBD agreed to work towards a series of goals called Aichi Biodiversity Targets. Target 9 addresses invasive species: “By 2020, invasive alien species and pathways are identified and prioritized, priority species are controlled or eradicated and measures are in place to manage pathways to prevent their introduction and establishment.” The authors of the review found that, while most countries have made progress on identifying and prioritizing some of the most prominent and threatening invasive species, “current management practices only target a handful” and “prevention of introduction and establishment lags far behind progress towards the reactive CBD goals.”

Biological invasions are expected to remain high across the globe; however, regions with a high Human Development Index (HDI) face different threats compared to regions with a low HDI. Due to increasing levels of international trade, high-HDI regions will continue to be threatened by introductions via pet and plant imports. Climate change and the coinciding biome shifts and changes in fire frequency are expected to aid in the establishment and perpetuation of invasive species in these regions.

Low-HDI regions have historically been less threatened by invasive species compared to high-HDI regions. As these regions join the global economy, they risk experiencing a much higher level of species introductions. Many of the planet’s biodiversity hotspots are found in low-HDI regions, making these hotspots more vulnerable to invasions as the potential for introductions increases. The authors found that the threat of introductions is at its highest in regions where “high levels of passenger air travel overlap with agriculture conversion.” Low-HDI regions are more limited in their capacity to respond to invasions compared to high-HDI regions and are more vulnerable to food shortages when invasive species disrupt agriculture.

“High risk in low-HDI countries could arise from coincidence between intensifying agriculture sectors and high levels of passenger air travel that is likely to transport arthropod pests. … Low-HDI countries could prioritize screening of passenger baggage for live plants, fruits or vegetables, which could host crop pests and pathogens.” – Early, et al. (2016) – photo credit: wikimedia commons

The authors state: “The intensities and global patterns of introduction and disturbance are changing more rapidly today than at any time during human history.” Introductions are not projected to slow in high-HDI regions, and low-HDI regions will be increasingly threatened as species already well established in high-HDI regions expand their reach. This is grim news, but it also presents an opportunity. Through cooperation and data sharing, our understanding of invasive species can greatly increase, and regions with greater access to resources can share such things with less fortunate regions. This is the hope of the authors as well: “We urge increased exchange of information and skills between regions with a wealth of invasive alien species experts and low-HDI countries that have less expertise.”

For more information about this review, go here. For more information about global trade in the modern era, check out the new podcast Containers.

Executive Orders on Invasive Species

As of January 20, 2017 we have a new administration in the White House, and with that has come a slew of executive orders. For better or worse, U.S. Presidents have the authority to issue orders that direct the policies and procedures of the agencies that make up the Federal government. Such orders have the same effect as federal laws. Thankfully, the U.S. Constitution sets up a system of checks and balances that keep one branch of government from exercising too much power over the others. In this way, executive orders can be challenged and, if necessary, overturned.

Of course, I don’t intend for this to be a political debate. There are plenty of other places out there that can take you down that rabbit hole. This is simply an introduction to invasive species and their run-ins with executive power. As evidence has mounted against invasive species, demonstrating the threat they can pose to human health and safety as well as to the economic well being of the nation, both state and federal governments have created laws and issued orders concerning them. Examples of such legislation include the Federal Noxious Weed Act of 1974 (which was superseded in 2000 by the Plant Protection Act) and the National Invasive Species Act (which deals specifically with ballast water management). Legislation such as this directs the actions of state and federal agencies in an effort to minimize the introduction and spread of invasive species and reduce the harm they may be having.

Executive Order 13112, issued by President Bill Clinton on February 3, 1999, gave further direction to Federal agencies in the nation’s ongoing battle against invasive species. One of its main directives was to create the National Invasive Species Council which, among other things, would be responsible for developing a National Invasive Species Management Plan.


The order begins by defining a few terms, including “alien species” (“any species…that is not native to that ecosystem”), “introduction” (“the intentional or unintentional escape, release, dissemination, or placement of a species into an ecosystem as a result of human activity”), “invasive species” (“an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health”), and “native species” (“a species that, other than as a result of an introduction, historically occurred or currently occurs in that ecosystem”).

Section 2 of the order describes the duties of Federal agencies “whose actions may affect the status of invasive species.” These include monitoring invasive species, preventing their introduction, controlling them in a “cost-effective and environmentally sound manner,” restoring native species, conducting research on invasive species, and promoting public awareness about the issue.

Section 3 establishes the National Invasive Species Council, and Section 4 describes its duties. The Secretaries of Interior, Agriculture, and Commerce are assigned as Co-Chairs of the council, and several other agencies are listed as council members. The council is directed to “oversee the implementation of this order” and, among other things, “prepare and issue a national Invasive Species Management Plan.”

Section 5 describes what the management plan should include and when it should be completed. The plan will include “performance-oriented goals and objectives and specific measures of success for Federal agency efforts concerning invasive species,” and should also provide a “science-based process to evaluate risks associated with introduction and spread of invasive species.” The Council was also directed to “assess the effectiveness of this order no less than once each 5 years” after its issuance.


Seventeen years and ten months after this order was issued, President Barack Obama issued an order that amended Executive Order 13112 and directed “actions to continue coordinated Federal prevention and control efforts related to invasive species.” It maintained the National Invasive Species Council while also expanding its membership and updating its duties. It also emphasized the impacts that invasive species can have on human health, specifically calling out “those species that are vectors, reservoirs, and causative agents of disease.” Additionally, it warned that “climate change influences the establishment, spread, and impacts of invasive species,” a subject that wasn’t addressed in the original order, and it encouraged making greater use of “technological innovation,” which had advanced considerably in seventeen years.

Collaboration appears to be a major theme of Obama’s amended order. In a couple different sections, “open data” is advised, as well as a call for Federal agencies to “develop, share, and utilize similar metrics and standards, methodologies, and databases,” and to “facilitate the interoperability of information systems.” The Feds are advised to use “tools such as challenge prizes, citizen science, and crowdsourcing” – a call that encourages more public involvement in the issue.

Both of these orders are worth reading for yourself. Clearly, government agencies take the threat of invasive species seriously. Perhaps in future posts we will explore some of the specific actions that these agencies are taking and the responsibilities they have regarding invasive species.

See Also: Introducing Invasive Species

Book Review: The New Wild

What if we were to look at invasive species with fresh eyes? Traditionally we have viewed them as interlopers hellbent on environmental destruction, but have we considered the good they can do? Should our efforts to eradicate them be tempered – eliminating them when it seems absolutely necessary, but accepting them when they are doing some good; welcoming them when they have something to offer. What does their presence mean anyway? What does it say about the ecosystems they inhabit and about us? Invasive species are convenient scapegoats, taking the blame for much of the ecological devastation that we started in the first place. Is that justified?

This is, essentially, the theme of The New Wild, a book by Fred Pearce that urges us to reconsider the ways we think, talk, and act towards invasive species. More than that, it is about dumping the idea that pristine nature (a mythological concept anyway, and one that is not all that useful) is the only true wild, and that nature invaded by alien species is a lesser thing that needs to be fixed. The truth is, nature is and always has been in a constant state of flux, and it is unconcerned about the provenance of the species that compose it. As Pearce puts it, if it’s doing “a useful job,” “it matters not a jot where a species comes from.”


Invasion biology is a relatively new field of study, stemming from the publishing of Charles Elton’s book, The Ecology of Invasions by Animals and Plants, in 1958. For thousands of years, humans have had a hand in moving species of all kinds around the planet, but it was in the latter half of the 20th century that our awareness of the ecological damage that some of these species can do really developed. Since then we have made great efforts to remove such species and put things back the way we found them. The zeal with which we have done so hasn’t always been justified or effective, and throughout what at times has felt like an all out war against foreigners, a profound sense of animosity and suspicion towards anything non-native has taken root in our psyche.

Pearce hopes to mitigate these feelings and get us to reconsider some of our actions. To start with, he calls into question the distinction between aliens and natives: “A broad time horizon shows there is no such thing as a native species. All lodgings are temporary and all ecosystems in a constant flux, the victims of circumstance and geological accident.” Also, “many aliens are so well integrated that they are assumed to be native,” and “species come and go so much, as a result of both human and natural forces, that conventional hard distinctions about what belongs where have long been all but meaningless.”

Instead of judging a species by its provenance, “we should treat species on their merits and learn a little tolerance and respect for foreigners.” While “being alien can sometimes be problematic,” it can equally result in the renewal of “flagging ecosystems, creating new space for natives and providing ecosystem services.” Seeing that those services are in place is what should really matter, and “[ecological services] are best done by the species on hand that do it best.” After all, nature is not a system of “preordained perfection,” but instead “a workable mishmash of species, constantly reorganized by the throw of the dice.”

In his criticisms of the field of invasion biology, Pearce investigates some of the “constantly recycled ‘facts’ about alien species.” He finds many of the claims to be unfounded and oft-repeated statistics to be blatant misrepresentations of the original studies. He concludes that “some of the most widely used statistics in the canon of invasion biology do not stand up.” To support his point, he offers several examples of how alien species have added to the biodiversity in certain ecosystems and he shares stories that “show how we instinctively blame aliens for ecological problems that may have a lot more to do with our own treatment of nature.”

Immigrant Killers by Carolyn King, one of many books making a case for the war on alien species.

Immigrant Killers by Carolyn King, one of many books published in the past few decades that makes the case for waging war on alien species.

In so many words, Pearce’s stance is that the classic “aliens are bad, and natives are good” approach is outdated – “nature doesn’t care about conservationists’ artificial divide between urban and rural or between native and alien species,” which means that our perception of aliens should shift from being “part of the problem to part of the solution.” Abandoned farmlands, secondary forests, recolonized waste places, urban sprawl, and other novel ecosystems across the globe offer explicit examples of species from all backgrounds coming together to create functional habitats. This is the new wild.

Pearce is not advocating that we throw in the towel and let invasive species run rampant: “It would be foolish to claim that alien species never do any harm or that efforts to uproot them are always doomed to fail.” His support for the new wild is “not a call to let it rip.” Instead, “conservation in the twenty-first century requires an open-minded assessment of what might work – not a sullen retreat into blinkered orthodoxy.” So, rather than try to stop the flux of nature (an act that is decidedly “anti-nature”), let’s see where it goes, alien species and all; and when we do decide to beat back invasives and intervene “to preserve what we like,” we should be mindful that nature may be “traveling in a different direction.” As Pearce writes, “the new wild is flourishing, and it will do better if we allow it to have its head.”


Obviously this is a controversial topic, but the ideas in this book are worth exploring further. Pearce’s notes are extensive, and I intend to read through many of his resources. Stay tuned for more posts. Meanwhile, you can listen to an interview with Pearce on this episode of Talking Plants. For a more critical veiw of Pearce’s book, check out these reviews by Los Angeles Review of Books and The EEB & Flow.


Ethnobotany: White Man’s Foot, part two

Earlier this year, as part of the ethnobotany series, I wrote about plantains (Plantago spp.), of which at least one species is commonly referred to as white man’s foot (or some version of that). Since writing that post, I happened upon a couple of other sources that had interesting and informative things to say about plantains. Rather than go back and update the original post, I decided to make a part two. Hopefully, you find this as interesting as I do. If nothing else, the sources themselves are worth checking out for the additional, fascinating information they contain about all sorts of plants.

plantago_boise capitol building

From The Book of Field and Roadside by John Eastman

Concerning their cosmopolitan nature: “Although both plantains [P. major and P. lanceolata] are Eurasian natives, they have long been thoroughly naturalized global residents; the designation ‘alien’ applies to them in the same sense that all white and black Americans are alien residents.”

In which I learned a new term: “Both species are anthropophilic (associate with humans); they frequent roadsides, parking areas, driveways, and vacant lots, occurring almost everywhere in disturbed ground. Where one species grows, the other can often be found nearby.”

Medicinal and culinary uses according to Eastman: “Plantains have versatile curative as well as culinary properties; nobody need go hungry or untreated for sores where plantains grow. These plants contain an abundance of beta carotene, calcium, potassium, and ascorbic acid. Cure-all claims for common plantain’s beneficial medical uses include a leaf tea for coughs, diarrhea, dysentery, lung and stomach disorders, and the root tea as a mouthwash for toothache. … Their most frequent and demonstrably effective use as a modern herb remedy, however, is as a leaf poultice for insect bites and stings plus other skin irritations. The leaf’s antimicrobial properties reduce inflammation, and its astringent chemistry relieves itching, swelling, and soreness.”

Even the seeds are “therapeutic”: “The gelatinous mucilage surrounding seeds can be readily separated, has been used as a substitute for linseed oil. Its widest usage is in laxative products for providing bulk and soluble fiber called psyllium, mainly derived from the plantain species P. ovata and leafy-stemmed plantain (P. psyllium), both Mediterranean natives.”

Plantain’s “cure-all reputation continues” today: Claims range from a homeopathic cancer remedy to a stop-smoking aid, “supposedly causing tobacco aversion.”

Claims of the healing properties of plantains abound in literature: “John the Baptist, in the lore of the saints, used it as a healing herb; Anglo Saxon gardeners called it the ‘mother of herbs.’ Plantain is ‘in the command of Venus and cures the head by antipathy to Mars,’ according to 17th century English herbalist-astrologist Nicholas Culpeper. Plantains also bear frequent mention in the works of Chaucer and Shakespeare.”

The worst thing plantains have to offer according to Eastman: “the airborne pollen they shed in large amounts, contributing to many hay fever allergies.”

Illustration by Amelia Hansen from The Book of Field and Roadside by John Eastman

Illustration by Amelia Hansen from The Book of Field and Roadside by John Eastman

From Weeds: In Defense of Nature’s Most Unloved Plants by Richard Mabey

Mabey’s too-good-to-paraphrase overview of plantain: “Plantain, ‘the mother or worts,’ is present in almost all the early prescriptions of magical herbs, back as far as the earliest Celtic fire ceremonies. It isn’t clear why such a drab plant – a plain rosette of grey-green leaves topped by a flower spike like a rat’s-tail – should have had pre-eminent status. But its weediness, in the sense of its willingness to tolerate human company, may have had a lot to do with it. The Anglo-Saxon names ‘Waybroad’ or ‘Waybread’ simply mean ‘a broad-leaved herb which grows by the wayside.’ This is plantain’s defining habit and habitat. It thrives on roadways, field-paths, church steps. In the most literal sense it dogs human footsteps. Its tough, elastic leaves, growing flush with the ground, are resilient to treading. You can walk on them, scuff them, even drive over them, and they go on living. They seem to actively prosper from stamping, as more delicate plants around them are crushed. The principles of sympathetic magic, therefore, indicated that plantain would be effective for crushing and tearing injuries. (And so it is, to a certain extent. The leaves contain a high proportion of tannins, which help to close wounds and halt bleeding.)”

On the inclusion of plantains in Midsummer’s Eve rituals: “On Midsummer’s Eve, great bonfires were lit in the countryside, and bundles of wild herbs thrown on them. Most of the plants were agricultural weeds, including St. John’s-wort, corn marigold, corn poppy, mayweed, mugwort, ragwort, plantain, and vervain.”

More about Midsummer’s Eve and the “future-foretelling powers” of this “divination herb, stretching sight into the future”: “On Midsummer’s Eve in Berwickshire, the flowering stems were employed by young women in a charm which would predict whether they would fall in love. It was a delicate, almost erotic process in which the sexual organs of the plantain were used as symbolic indicators. Two of the ‘rat’s-tail’ flowering spikes were picked, and any visible purple anthers removed. The two spikes were wrapped in a dock leaf and placed under a stone. If, by the next day, more anthers had risen erect from the flowering spikes, loves was imminent.”

"Greater - or 'ratstail' - plantain had by this time been nicknamed 'Englishman's foot' by the Native Americans, who had witnessed its prodigious advance in the white man's wake." - Richard Mabey, Weeds: In Defense of Nature's Most Unwanted Plants

“Greater – or ‘ratstail’ – plantain had by this time been nicknamed ‘Englishman’s foot’ by the Native Americans, who had witnessed its prodigious advance in the white man’s wake.” – Richard Mabey, Weeds: In Defense of Nature’s Most Unwanted Plants

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What Shall We Do About Invasive Species?

I think about invasive species a lot. This blog doesn’t really reflect that though. I have been avoiding a deep dive into the subject mainly because there is so much to say about it and I don’t really want this to become “the invasive species blog.” Admittedly, I’m also trying to avoid controversy. Some people have very strong opinions about invasive species, and I don’t always agree. But then an article entitled Taking the long view on the ecological effects of plant invasions appeared in the June 2015 issue of American Journal of Botany. Intrigued by the idea of “taking the long view,” I read the article and decided that now is as good a time as any to start exploring this topic in greater depth.

However, before getting into the article, we should define our terms. “Invasive species” is often used inappropriately to refer to any species that is found outside of its historic native range (i.e. the area in which it evolved to its present form). More appropriate terms for such species are “introduced,” “alien,” “exotic,” “non-native,” and “nonindigenous.” The legal definition of an invasive species (according to the US government) is “an alien species that does or is likely to cause economic or environmental harm or harm to human health.” Even though this definition specifically refers to “alien species,” it is possible for native species to behave invasively.

These terms refer not just to plants but to all living organisms. The term “noxious weed,” on the other hand, is specific to plants. A noxious weed is a plant species that has been designated by a Federal, State, or county government as “injurious to public health, agriculture, recreation, wildlife, or property.” A “weed” is simply a plant that, from a human perspective, is growing in the wrong place, and any plant at any point could be determined to be a weed if a human says so. (I’ll have more to say about human arrogance later in the post.)

Rush skeletonweed (Chondrilla juncea) - labeled a noxious weed in Idaho

Rush skeletonweed (Chondrilla juncea) – labeled a noxious weed in Idaho

The authors of the AJB article (S. Luke Flory and Carla M. D’Antonio) begin by clarifying that “most introduced species are not problematic.” Those that are, however, can “cause significant ecological and economic damage.” This damage is well documented, and it is the reason why billions of dollars are spent every year in the battle against invasive species. But there is a dearth in our research: “less is known about how ecological effects of invasions change over time.” The effects of invasive species could “increase, decrease, or be maintained over decades,” and “multiple community and ecosystem factors” will determine this. For this reason, the authors are calling for “concentrated efforts to quantify the ecological effects of plant invasions over time and the mechanisms that underlie shifting dynamics and impacts.” Armed with this kind of information, managers can better direct their efforts towards invasive species determined to be “the most problematic.”

The authors go on to briefly explain with examples why an invasive species population may decline or be maintained over time, highlighting selected research that demonstrates these phenomena. Research must continue with the aim of improving our understanding of the long term effects of plant invasions. The authors acknowledge that this “will require carefully designed experiments,” “patient and persistent research efforts,” and significant amounts of money. However, they are convinced that through a widespread collaborative effort it can be done. They encourage researchers to deposit data obtained from their research in open source online repositories so that future meta-analyses can be conducted. The information available in these online repositories can be used to develop management plans and help predict “future problematic invasions.”

Considering the amount of time and resources currently spent on confronting invasive species, the approach proposed by the authors of this article is quite reasonable. It seems absurd to continue to battle a problematic species that will ultimately be brought down to more manageable levels by natural causes. It also seems absurd to battle against a species that is essentially here to stay.

Field bindweed (Convulvulus arvensis) - labeled a noxious weed in Idaho

Field bindweed (Convulvulus arvensis) – labeled a noxious weed in Idaho

And that brings me to the point in which I make enemies. Take a look at the terms defined earlier. When we talk about introduced species, we are referring to introductions by humans, whether purposeful or accidental. An “alien” species introduced to a new location by wind, water, or animal (other than human) would be considered a natural introduction, right? If that species becomes established in its new location, it would simply be expanding its range. If a human brought it there, again whether purposefully or accidentally, it would be considered an exotic indefinitely.

Humans have been moving species around since long before we became the humans we are today in the same way that a migratory bird might move a species from one continent to another. At what point during our evolution did our act of moving species around become such a terrible thing?

I will concede that our species has become an incredibly widespread species, able to move about the planet in ways that no other species can. We also have technological advances that no other species comes close to matching. In the time that our species has become truly cosmopolitan, the amount of species introductions that we have participated in has increased exponentially. Leaving ecological destruction in our wake is kind of our modus operandi. I don’t want to make excuses for that, but I also don’t see it unfolding any other way. Give any other species the opportunities we had, and they probably would have proceeded in the same manner. Just consider any of the most notorious invasive species today – “opportunist” is their middle name.

More and more, as we are able to see what we have done, we are making efforts to “fix it.” But how de we rewind time? And if we could, when do we rewind back to? And how do we not “ruin it” again? The earth does not have a set baseline or a condition that it is supposed to be in at any given time. The earth just is. It is operating in a state of randomness, just like everything else in the universe. Any idea of how the earth must look at any given time is purely philosophical – conceived of by humans. I’m not saying that we shouldn’t try to repair the damage, but we should acknowledge that the repairs we’re trying to make are largely for the perpetuation of our own species. Yeah, we’ve developed a soft spot for other species along the way (thankfully), but ultimately we’re just trying to maintain. The earth, on the other hand, would be fine without us.

So, what shall we do about invasive species? I’m not entirely sure. The only thing I’m certain of is that I will continue to ruminate on them and potentially bore you with more blog posts in the future. Until next time…

Puncturevine (Tribulus terrestris) - labeled a noxious weed in Idaho

Puncturevine (Tribulus terrestris) – labeled a noxious weed in Idaho