National Geographic News
Photo of a giant Aldabra tortoise in Mauritius.

Giant Aldabra tortoises are a non-native species on the islands of Mauritius. The country introduced them in 2004 after losing all its large tortoises.

Photograph by Jack Abuin, ZUMAPRESS/Corbis

Emma Marris in Missoula, Montana

for National Geographic

Published July 24, 2014

What should be done with the wattle-necked softshell turtles on the Hawaiian island of Kauai?

The turtles came from China, starting in the 1850s, brought by sugarcane farmers who liked them as soup. Today, they're endangered in China and considered invasive—the term for non-native species that cause undesirable effects—in Kauai. But conservationists don't believe the animals are safe from hunting in their home range, so there's little point in boxing them up and sending them back.

It's a head scratcher: Should we remove the turtles from Kauai to preserve the native ecosystem there—the turtles could potentially eat native fish—and risk the extinction of their species, or should we keep them alive in Hawaii?

Those kinds of knotty questions are becoming more commonplace in ecology, as global change accelerates. And so a new attitude is emerging that's less reflexively hostile toward invaders. It was much in evidence at a symposium held last week at the North American Congress for Conservation Biology in Missoula, Montana. I participated as a journalist but not a disinterested observer: I've argued in the past that it's time for a more nuanced approach to the non-native plants and animals among us.

Invasive species are scary. It was ecologist Charles Elton, back in the 1950s, who introduced the militaristic "invasion" metaphor to describe exotic plants and animals—but there's no question some can be extremely destructive.

The brown tree snake has eaten a dozen kinds of forest birds in Guam to extinction; zebra mussels clog pipes around the Great Lakes; the common house cat turns out to be, in Australia, a mercilessly effective killer of cute, fluffy marsupials like the bilby and the numbat.

As scientists have sounded the alarm about these pests, the public has gotten the message. Citizen groups rip out non-native plants. Native gardens have become increasingly popular, both as ways to celebrate the unique flora of each region and as tiny hot spots of diversity. Native trees provide food for native bugs, which feed native birds. Food chains developed over thousands of years of co-evolution unfold in our backyards. We're even going native in the kitchen, with fine restaurants increasingly focused around locally hunted, foraged, and grown ingredients.

So we've learned, scientists and lay people alike, that native species are good and non-natives are bad.

Julian Olden, a biologist at the University of Washington, Seattle, who co-organized the symposium, recently polled nearly 2,000 ecologists. Among his findings: A substantial number of them said they would immediately eradicate a hypothetical non-native forest plant, even if it were shown to have no effect on the forest. Olden calls this the "guilty even when proven innocent" approach.

That kind of approach is not very useful on a rapidly changing planet.

Exotics Are Everywhere

Climate change is making it harder even to decide who the invaders are.

How, scientists at the symposium wondered, do you define "native" on a warming planet, when plants and animals are already moving toward the poles or up mountainsides in search of climate conditions they can tolerate? Should we consider them "invasive" in their new homes? Regardless of what we label them, conservationists will be reluctant to remove them from their new environs—to do so would stymie their chances of adapting to the warmer future we're creating.

And then there are the non-natives that we actually like. Most domestic crops are exotic in most of the places they're grown, but there are even wild exotics that "do good," forming useful relationships with native species.

Edwin Grosholz of the University of California, Davis, told the recent symposium about one such relationship. On beaches in his state, non-native spartina grass has become important habitat for the endangered California clapper rail, a plump shorebird with a downward curving bill more at home on land than in the air. A project to rip out and poison the spartina—which grows in dense swaths that exclude many other shorebirds—saw clapper rail numbers go tumbling downward.

There are other examples like that. The endangered southwestern willow flycatcher nests in "invasive" tamarisk shrubs. Many native (and beautiful) Hawaiian flowers are now pollinated by the Japanese white-eye bird—because the native pollinators have been driven extinct by other non-native species.

Should we impose further risk on already endangered natives by severing these relationships? Or should we admire the resilience of nature and let such "well-behaved" exotics stay?

Weirdest of all is the puzzle of the invasive species that are themselves endangered, like the wattle-necked turtle. Dov Sax, an ecologist at Brown University in Providence, Rhode Island, and symposium co-organizer, reported that 15 percent of mammals and 10 percent of birds that have been introduced in non-native habitats are under threat in their home ranges.

Hippos, vulnerable to extinction in sub-Saharan Africa, are multiplying in the lakes of Colombia, after being imported by drug lord Pablo Escobar. The red-crowned Amazon parrot is endangered in its home in northeast Mexico, but flourishes in noisy flocks in cities in California and Hawaii. What do we do with such cases?

Leave them alone, more and more conservationists are arguing, and stop focusing obsessively on categorizing species as native or non-native. Mark Davis, an ecologist at Macalester College in St. Paul, Minnesota, once considered himself an "invasion biologist"—but not anymore. "I am actively trying to get the field to retire the invader narrative," he said in Missoula.

A Good Thing, Not the Only Thing

After all, nativeness is just one environmental value, and arguably not as important as preventing extinctions and preserving biodiversity. In some cases we can best serve biodiversity by leaving the non-natives alone or even—brace yourself, now—introducing them on purpose.

This is the thinking behind, for example, installing the Aldabra tortoise on the islands of Mauritius. The islands lost their own large tortoises, and the fruiting plants that formerly had their seeds moved around by these fruit-loving reptiles have been on the decline. A tortoise that's related to the island's large tortoises—a non-native from the Seychelles in the Indian Ocean that was intentionally introduced in 2004—is now handling some of that work.

Most of the time, for the time being, conserving species still means focusing on supporting them in their historical habitats, planting natives and removing non-natives. We can and should do that in places where it is feasible and important to us.

As native gardening guru Douglas Tallamy has shown us, nothing beats a native tree for supporting biodiversity. Keeping whole landscapes completely native will require more and more active management as time goes on—but for some special places, it will probably be worth it.

But the weirder, tougher cases will keep coming up. As climate changes, as the species we've already moved around establish themselves in their new homes, we'll be called on more and more to choose between the needs of a threatened species and the historical continuity of an ecosystem.

Which matters most to you is a personal decision. For me, though I highly value the particular distribution of life that makes each place unique, species survival trumps historical fidelity. Ultimately, I care more that species exist than that they stay where they're "supposed" to be. Let the turtles stay on Kauai.

I also believe that hating non-native species is counterproductive and unfair. Even the deadly tree snakes in Guam, responsible as a species for so many extinctions, are not evil as individuals. They have no idea they aren't in the right place. They're just snakes being snakes.

It makes more sense to be angry at the humans who moved a harmful species to a new place—but in general, harmful introductions were accidents or were undertaken by people who meant well.

And most of the extinctions and population declines that mar our beautiful Earth aren't caused by exotic species. They're due to development that is destroying habitat, often needlessly. That's the real bad guy. If you must hate something, hate mindless development.

When my kids and I see Queen Anne's lace by the roadside or the lemony yellow flowers of the common mullein—both very common non-native weeds in the United States—I don't scowl. I don't see those flowers as evil villains or even as a blemish on the landscape. They're unlikely to drive any other species extinct. They don't know they're on the wrong continent. And no matter where they are, they're still beautiful.

Emma Marris is the author of Rambunctious Garden: Saving Nature in a Post-Wild World.

58 comments
C. Dufour
C. Dufour

at a time where bumblbees and honeybees are suffering from massive die-offs, im keeping my dandelions!

John Measey
John Measey

Q What should be done with Madagascar's threatened lemurs?  

A Don't let a well-meaning billionaire take them to his own island. 


One of the arguments taken up in this opinion piece by Marris is that threatened species could benefit from extralimital populations:


“In some cases we can best serve biodiversity by leaving the non-natives alone or even—brace yourself, now—introducing them on purpose.”


The whole idea of translocation of threatened species is not a new idea, and one which the IUCN and the scientific community take very seriously. Extralimital introductions of threatened species for conservation purposes are themselves very rare (note that other examples given – hippos, parrots – were not introduced for conservation reasons), and the IUCN have specific best practice guidelines about what should be done before any such introductions (https://portals.iucn.org/library/sites/library/files/documents/2013-009.pdf). Although it would be foolish to dismiss the idea that there would be conservation reasons to move threatened species to new extralimital localities, I’d suggest that these would in fact be very seldom employed.


I’ve “cherry picked” the next example, mostly as it’s the only recent one I can remember where someone suggested moving a threatened species to an extralimital location that seemed ideal to them and their “advisors”. The idea was then roundly condemned by almost every conservation authority that responded, most prominently the IUCN. The example, serves to show that many well-meaning people and their supposed experts think the same way as the Marris article suggests. However, the reality is that conservation science is not as simple as being well-meaning.


http://green.blogs.nytimes.com/2011/04/19/branson-a-man-with-an-island-for-lemurs/?_php=true&_type=blogs&_php=true&_type=blogs&_r=1


Richard Branson was so moved by the plight of threatened lemurs that he decided he would “save” some by moving them to his own island so that they could live without the threats that they face in their native Madagascar. On the face of it, the suggestion appears very reasonable. However, it completely ignores potential that the addition of lemurs might have on the ecology of Branson’s island. 

Daniel Edrich
Daniel Edrich

Over a decade ago an NGO appproached our CSD claiming that we had weeds and they would like permission to remove them.  We were promised that re-planting would be immediate and that there would be NO erosion NOR adverse effect to hydrology or wildlife.  

Millions of dollars later, our fore dune is blown-out, wetlands have drained and much of our wildlife has disappeared.

The re-planting was never done and our Contractors are telling us that our now moving dunes are "natural."  Literally we've gone forest to desert, from fore dune to no dune with a Base Flood Elevation loss of twelve feet.

I wouldn't trust these fraud "restorationists" any further than I could spit.

Dave Richardson
Dave Richardson

Ms Marris conveniently omits to mention that the symposium of the North American Congress for Conservation Biology on which her piece is based was one that was arranged to bring together some of the most vocal contrarians in the field – a minority group who seem to think that they are doing the world a favor by pointing about how futile it is to fight invasive species.


It is becoming rather tiresome to address the same arguments over and over again in response to the views in articles like this. What is worse is that the message that the contrarians espouse has the potential to derail crucial conservation actions.


A key part of the argument of the contrarians is that “not all alien species are bad”. Of course they are not! Only those on the extremist fringe say anything different. Most non-native species are benign or beneficial, indeed essential, for human wellbeing. 


The contrarians then go on to say – “Yes, that’s what you say, but the ALIENS ARE BAD attitude pervades your science”. Really? Definitely not the version of science that I practice! The invasion science that I practice every day is based on objective assessments, formal risk assessments, and painstaking efforts to resolve conflicts of interest and arrive at win-win situations.


We all know that invasive species are but one component of a basket of human-induced environmental problems that require pragmatic attention. As they rightly point out, native species also cause major problems when they become “weedy”, thanks to human-induced changes to ecosystems. Such species also merit action.

However, huge impacts that transform ecosystems, cause massive damage and drive trophic cascades are almost always driven by non-native species, not native ones. There are obvious reasons for this that have NOTHING to do with being xenophobic or being “counterproductive and unfair”. For one thing, non-native species usually leave their natural enemies behind when they are introduced to new areas by humans. This allows many to proliferate and to cause impacts due to their large numbers. Another thing, non-natives often introduce novelty to their receiving environments, for example the ability to fix nitrogen in nutrient-limited ecosystems, or by introducing radical new connections in food webs (e.g. brown tree snakes on islands).


The contrarians then say – “We are not arguing that SOME non-natives are not damaging, but this does not mean that non-natives in general should be persecuted”. Unfortunately, our ability to predict which non-natives will establish, spread and cause massive impacts is imperfect (which is not surprising given the huge complexity of all the interactions that mediate success at each stage of the introduction-establishment-invasion continuum!). Another problem is that many non-natives that cause massive problems only do this a long time after they were introduced – often many decades later. Furthermore, some non-natives are benign in some parts of the world, but cause major damage in others. Yet another problem is that major important impacts of non-natives are not terribly obvious – they are not easy to see or measure – but are very important nonetheless. Examples are the many types of impacts of invasive species on plant reproduction ecology that are only beginning to be appreciated.


All of this means that we must follow a precautionary approach. We have some knowledge of what species pose a high risk of causing damage if introduced. So, it makes sense to do the risk assessment and if it turns out that the risk is high, rather prevent the species from coming in, and if it is already here, see whether it can be eradicated.  For species that are already widespread, eradication is probably impossible, so again apply objective risk assessment protocols, consult widely, address potential conflicts of interest, and then prioritize management actions – apply limited funds to the most important problems and those with the best chance of success.  These are issues that the vast majority of scientists working on invasive species busy themselves with, not with the obsessive elimination of anything non-native!


Some of you may be interested to read a more detailed response by Tony Ricciardi and myself to other criticisms of invasion ecology:


http://onlinelibrary.wiley.com/doi/10.1111/ddi.12150/abstract


A. Kessler
A. Kessler

Nativism is destroying our parks, here in San Francisco. Here the "native" environment -- as of the nativists' favorite-date "1776", anyway -- was sand. We are an arid peninsular tip surrounded by salt water -- one giant sand-dune stretched from the ocean to the bay, and the rest was mostly dry scrub. Everything we have here, in this city, including our fresh water, was brought-in or built by someone.


So here the nativism is a recent hysteria, building on similar xenophobia outbreaks before, this time a supposed-longing for a past which San Francisco never had. Citizens here over two centuries have planted gardens and parks and playgrounds and walkways with all sorts of "foreign" foliage -- providing recreation for citizens, habitat for wonderful urban animals -- but now all of that has become a financial windfall for nurseries and gardeners and landscapers whose wallets benefit, greatly, from the faux-nativist craze.

Parks used to have little signs in them saying "Don't pick the flowers". Now brigades of citizen "volunteers" parade regularly through our few green areas here -- SF has less trees than most major cities -- ripping out plants and planting little colored plastic flags in their place. When the nursery-propagated "native" replacements finally appear they die, regularly, and regularly they get re-replaced, and yes all of this repetitive cycle is very expensive. But we're a very rich city, it's only money, and noblesse oblige.

It is odd that a city, state, and national culture founded by immigrants and so proud of its immigration history should adopt "nativism" as its leading urban landscaping policy. That is a contradiction. I just hope that, whatever the supposed-justification, the result will not be even fewer trees, and landscapes of dead brown nativist plant-experiments -- but that is where San Francisco seems headed for now.

Benjamin Vogt
Benjamin Vogt

Maybe we should be looking at the deeper issues here -- we cause climate change, we cause extinctions, we exacerbate drought and deluges and swings in the jet stream. It's fine to adapt, embrace the change that's upon us, but we need to be looking at the deeper socio-economic causes at play here, and if our ethical codes toward life (other species and our own, especially our future generations) are up to snuff. We show no intention or ability to think about the future. 

Look at the annihilation of prairie in the Great Plains, North America's Amazon rainforest, that could store massive amounts of carbon in the soil; we continue to eradicate it, watch topsoil slide away, poison the land and water with agricultural chemicals, leach out soil life and erase food sources for pollinators, but we don't learn to farm smarter. Yes, the real bad guy is us -- we are facing an ethical imperative here and failing badly at adapting in more profound, deep, and fundamental ways. 

We can embrace non native species in new habitats, but the fact is 30% of global plant species may be gone by 2060, and they will take a massive amount of animals with them -- no amount of non natives will make up for that erasure, and we have no idea of the repercussions (will we do: more disease, less free ecosystem services, etc). Plant your nonnative whatever out back, but recognize that this act echoes a larger system of our navel gazing and self-privileging in the anthropocene.

Philip Rutter
Philip Rutter

I think you're missing some nuances to the conversation yet; for example: "the term for non-native species that cause undesirable effects" .  Well, not my definition, and I work here, a lot.  I would attempt to refine that as "the term for a non-native species known to be capable of displacing native species, and demonstrated to be able to rapidly expand its populations and extend its "conquered" territory."  A good deal more threatening, and I think precise, than the first.


Another point; a great many conservation workers have been taught the attitude of "remove aliens first and research later" - without necessarily understanding why.  There is an excellent reason: many - as in MANY- very destructive species, like kudzu, water hyacinth, starlings, Ailanthus - have been documented as having a "latent" period after introduction - like 10- 50 years - before they suddenly and without obvious reasons turn fiercely destructive and "invasive."  Unless you have a tremendously good reason for an introduction - why take the chance?  You and I actually do already have enough native pretty plants, or animals.  


I am entirely on your side, though; that these decisions need to be made, one at a time and not by simplistic outdated rules.  Absolutely, yes; there are reasons for humans to move other species around.  If I had my druthers, I'd likely clear Molokai of all humans and the critters we brought with us (Polynesians too, guys) and turn it back to pre human species - plus all the bonobos I could catch and move.  Ok, silly.  But. 


On a more sensible note; most of the conifers native to the North American west are in danger from climate changing faster than they can migrate.  Some are in imminent danger of being reduced below reproductive critical populations.  White bark pine, for example; lives on mountain tops; and jumps from one to the next only very, very rarely.  I would say it makes sense, now, to introduce white bark pines onto mountaintops just north of their historic range.  Other conifers may be in urgent jeopardy too.  Risk to other species?  None, I think.  Benefits?  Many, I think.  Time to try a bit; and find out.

Jake Williams
Jake Williams

Man is part of nature. Expanding one's habitat is the natural course of action for successful species. The results of that expansion is what Darwin called natural selection. If you value other species more than your own, then I guess you would be a suicidal organism. Nature is unlikely to select you for survival. Uh-oh. 

carlos rodriques
carlos rodriques

At last a breath of fresh air on this subject.  It's sad to see the wasted energy, time and dollars being spent on making landscapes "pristine."  Who truly knows what existed within any window in time on any landscape.  We have our memories, our models, our stories and our fantasies.

Thank you for standing up for this unpopular view.

Mary Castrovilla
Mary Castrovilla

From the article above:



“And most of the extinctions and population declines that mar our beautiful Earth aren't caused by exotic species. They're due to development that is destroying habitat, often needlessly. That's the real bad guy. If you must hate something, hate mindless development.”

RIGHT ON!!



Chrissie Raffensperger
Chrissie Raffensperger

Development makes me scowl as well. In Florida they're going to destroy what little bit of forest is left to make room for a Walmart. Unfortunately, this forest is one of the rarest in the world only found in Florida and I think like Cuba? Hopefully, people will start spending more time fighting such actions and less time pulling out non-native species. 


Matt Chew
Matt Chew

The distribution of life on the planet has a history. It's a history of accidents, period. Accidents of some kinds have been more likely than others at different times, depending on factors like the distribution of land masses, temperature ranges, oxygen levels in the atmosphere, and most recently the fact that one species learned about the difference between 'here' and 'there' and developed some technologies for getting around. They carried members of some other species around with them on purpose. They carried others by accident, mostly without realizing it (or caring, when they noticed).

Individuals of that species relate to each other primarily by trading stuff, much of it over very long distances. It was no accident that they sought ever faster and more efficient ways of moving ever larger amounts of stuff from wherever it was to wherever it was wanted. Individuals of other species (not all species or course, but those with particular life histories and sizes and behaviors rendering them susceptible) continued to get dragged along; still mostly by accident, and some in large numbers.

A great many of the basic technologies and traditions of of transportation, manufacturing, and commerce were established long before understanding biology was much more than a diversion for minor aristocrats with time on their hands. For a long time they argued about things like why there were so many kinds of living things, and even about whether it was possible for any of those kinds to die out.

One thing biologists were very bad at for a very long time was realizing that they, too were individuals of a species, susceptible to all the hazards and accidents of existence, including extinction. Biologists always seemed to think of themselves as outsiders looking in. Many felt entitled to look at strange plants and animals in exotic places, and to attend meetings anywhere in the world that suited them. "All this technology and commerce and travel is obviously necessary for biologists," they said, "but shame on the rest of you and what you've been doing and all the accidents you've caused for two or three millennia before we arrived." "Oh, and by the way," they added, "kill that thing over there. We think it's in the wrong place. That's how we feel about it. It's our job to tell you that, and yours to believe that how we feel is vitally important to the future of the planet. We'll have no more accidents."

Nevertheless, the accidents continued.

Kirk Mantay
Kirk Mantay

The truth is in the middle.   The fact is that most non-native species never get a foothold.  Those that do tend to be aggressive, allelopathic, etc.  I know that some people "feel bad" for invasive rats.  And you are welcome to come to Baltimore and collect as many of them as you like.  Please take with you the English Ivy that has ravaged our native Oak forests, the invasive Phragmites that has eliminated most species of fish and wildlife from our tidal marshes, and the Tree of Heaven that poisons the soil so other native plants cannot even germinate.   This is actual "stuff."  Not feelings, or hand-wringing over someone's managing invasive weeds.


However, what this article proposes is feel-good pseudoscience, and I'm disappointed to see National Geographic give it any mention, let alone web space.  "See, a pretty turtle!"  Come on, now. 


The truth is in the middle, scientifically, because we haven't removed a single invasive species from North America in 100 years.  Despite millions of dollars and millions of barrels of chemicals and intentional forest/prairie/wetland fires across millions of acres.  The bad critters and plants are all still here.  100% of them.  


So the question that should have been posed by this author is, "What do we value more?"  What DO we value more?  If we value native ducks, then we have to keep invasive plants with no habitat value out of the marsh.  If we value otters, we have to (try to) make sure their favorite foods aren't annihilated by competing, non-edible invaders.  But, if we value, "Awwww, nature is cute,"  then yes, a tree is a tree is a tree.  A turtle is a turtle.  A bird is a bird.  That's really the point of this article, and it stands in direct antagonism to everything National Geographic is about - why places are different, why the things that live in those places are different, and valuable, and important to save.  


So....you guys have fun with your European cowbirds, knocking endangered native birds' eggs out of the nests.  That's nature, right?

Millie Trees
Millie Trees

Thank you, Ms. Marris for writing this and to NG for publishing it.The war on non-native plants and animals is now a multi-billion dollar industry with all the power enjoyed by business in our country.Scratch the surface of those who defend these destructive projects and you will usually find someone who is making their living at it.


I agree with every argument Ms. Marris has used, but my reasons for arriving at her viewpoint are a bit different.  I watched my public parks and open spaces being destroyed by the native plant movement in the San Francisco Bay Area because our urban forest is almost entirely non-native.  Much of California was treeless prior to the arrival of Europeans.  The native landscape is predominantly grassland and scrub and the nativists are determined to “restore” that landscape.  Weedy messes are the usual result.


Aside from the aesthetics of this destruction, all of our open spaces are being sprayed with toxic herbicides required to prevent the trees from resprouting and to destroy vegetation.  Non-native blackberries are sprayed with herbicides while they are fruiting.  How many birds and animals have been poisoned by these projects?  We will never know.


Rodenticides are being aerial bombed on islands to kill mice and rats.  Untold hundreds of birds are killed in the process.  Barred owls are being shot by US Fish & Wildlife based on the belief that it will benefit another bird.  The barred owl is native, but another bird is considered rarer, so the barred owl must be killed.


In other words, death and destruction is the consequence of nativism.  All other arguments against nativism are just rhetorical to me.  Read more about these projects and the bogus reasons for them at million trees dot me.

Tom  Stohlgren
Tom Stohlgren

As a teacher of critical thinking in the sciences, I warn my students about overly simplistic, illogical, pseudo-science. Sadly, these are all evident in Emma Marris’s recent opinion piece entitled “It's Time to Stop Thinking That All Non-Native Species Are Evil. How can we best come to terms with the exotic species that surround us?” First, using the words “all non-native species” and “evil” in the title of the article create an unsupportable, irrational premise. Few reasonable people would ever claim “all non-native are species are evil.”  For decades, scientists, land managers, and policymakers have rightly concerned themselves only with harmful invasive species: a small subset of non-native species. Therefore, the word “all” in the title is totally irrational and unsupported — a hasty generalization (a common fallacy). Likewise, reasonable scientists, managers and policymakers rarely use loaded Biblical terms such as “evil” to describe how selected non-native, invasive species affect the environment, the economy, or human health. Terms such as evil, good, and bad may be appropriate for Sunday School, but seem out of place for National Geographic. 


Marris appears fond of setting up illogical, false-dichotomies such as, “What should be done with the wattle-necked softshell turtles on the Hawaiian island of Kauai?” The turtles are endangered in their native land in China, but they may cause undesirable effects in Kauai. Marris offers only two choices: boxing them up and sending them home or keeping them as destructive pets in Hawaii. She never discusses other alternatives. A third alternative might be looking for less-sensitive areas to house the turtles temporarily until they can be safely protected in China (where they evolved). The only “head scratcher” is why Ms. Marris offers only two, unsustainable options. Let’s find a less damaging temporary home for the turtle, while not endangering the already threatened native flora and fauna in Kauai.


Marris is wise to point out that some highly invasive non-native species can be extremely destructive (e.g., the brown tree snake in Guam to extinction; zebra mussels, the common house cat in Australia). Sadly, Ms. Morris over-generalizes that for ”scientists and lay people alike, that native species are good and non-natives are bad.”  I believe that most reasonable scientists try to avoid qualitative, judgmental terms such as good and bad. We do, however, quantitatively assess risks to the environment, the economy, and to human health. When those risks are high, the public rightly expects us to reduce those risks and protect native species and ecosystems, which happens to be a policy and management obligation in many national parks and public lands for the sake of future generation (who may not be as accommodating of harmful invasive species as Marris seems to be). Where risks are uncertain, applying the precautionary principle may be a wise choice.


I'd agree with Ms. Morris’s sophomoric claim that, “there are non-natives that we actually like such as our domestic crops.” Still, the public would be right to frown upon cornfields throughout Yellowstone National Park.  Another unfortunate, illogical. false dichotomy is presented when rare native species use harmful invasive species for temporary habitat (e.g., non-native spartina grass has become important habitat for the endangered California clapper rail; the endangered southwestern willow flycatcher nests in "invasive" tamarisk shrubs). An alternative management action is to restore native habitats first, then remove the harmful invasive species. Native species conservation remains a viable long-term goal.


Morris advocates ”planting natives and removing non-natives only “in places where it is feasible and important to us.” Important to us? How about if it's important to sustain native species and ecosystems. Is it up to Morris to decide what's important for all the other species on Earth? Will future generations ask what happened to the native species and ecosystems or does Marris know that too?


When Morris defends the individual brown tree snake on Guam is she also defending the individual Africanized honey bee in 80,000-strong swarm that killed an elderly woman in California? While she defends the rights of the individual twenty-foot long, invasive python in the Everglades, who is defending the individual rights of thousands of native rabbits, bobcats possums, and other native species that are rapidly disappearing.


Marris claims that modern extinctions are not being caused by exotic species. I can recommend several scientific studies that show she is ill-informed and naïve. Up to 95% of modern extinctions on islands are caused by harmful invasive species and the humans the brought them.


When Marris shows her kids the beautiful yellow flowers of the leafy spurge by the roadside, I hope she tells them that nature isn't a beauty contest. That leafy spurge is poisonous to cattle and deer, and it has harmed the economy of many ranches in Montana. The fact that Marris might find it beautiful is of little consequence to those ranchers. 


Sandra Neary
Sandra Neary

Very thoughtful and well phrased article, your point being particularly made as I gather herbs and medicinal plants such as mullein to dry and know that many of those plants are "non-native", brought to North America to do exactly what I do with them.  All of the examples, both in the article and in the comments, were a result of the man's intervention. As one commenter noted, the most "invasive" species of all is mankind.  Climate plays a role in the independent movement of species, certainly.   Can any country actually stop import or export of seeds, insects, invasive mussels, odd snails, etc? Some try but I believe that any contact with other countries, any participation in global travel or trade, will allow some "invasion" as well as "escape".  This is certainly true of virus and bacterium.  Is there an answer?  Should we stop "fighting"?  I don't think so, for either question.    

Dan Alger
Dan Alger

Zebra mussels are a problem because they are an invasive species? Because they might make native pipes extinct? They would be a problem if they were a native species.

ami l.
ami l.

I think this could be a dangerous attitude to adopt towards non-native species. The slow migration of species to a new habitat because of changing climate is vastly different from the importation of new plants and animals to an ecosystem. 


This summer I've been battling Japanese Beetles, Asiatic Garden Beetles, Lesser Celandine, English Ivy, Asiatic Bittersweet and Garlic Mustard. All of these species of insects and plants were non-natives introduced accidentally or intentionally. The Lesser Celandine has absolutely destroyed all the spring ephemerals that would normally be growing in a yard like mine. This spring there was a literal carpet of LC that prevented anything else from growing, and it does absolutely nothing for any native insects or animals. The vines were choking five of the fourteen trees in our yard when we bought our house a couple of years ago. The whole area was on its way to becoming a seasonal mono-culture with LC in the spring and the vines the rest of the year. How could that possibly be good?!


Perhaps each instance needs to be evaluated on a case-by-case basis, but to state overall that it might be ok to accept non-native invasive plants and animals (pythons wreaking havoc in Florida anyone?) is foolish and would only be an open invitation to big box stores and unscrupulous garden centers to carry plants that are known to be trouble-makers just because they're pretty & vigorous growers that are easy to take care of. Mono-cultures are just bad, bad news.

Swiftright Right
Swiftright Right

Cute turtles aside the Midwest is being over ran with Chinese stink bugs and the rocket scientists are trying to get the go ahead to import fricken 2 inch long Asian hornets (which are know for being especially aggressive) to combat them. Fun fact these hornets can cause renal failure in humans with as few of 4 stings.  10 stings being enough to kill a small person


Seen any Ash trees in the Mid Atlantic and eastern side of the mid west lately?  Probably not since the emerald ash borer is driving them to extinction. 


Many Americans have never even seen an Elm tree, trees which use to cover most of our continent thanks to imported elm beetles spreading Dutch elem disease. 


Personally I dont want to see an ecologically near dead planet were all the species have been homogenized based on what can survive contact with humans and a handful of globally dominate super species of insects, plants and animals.

Jim Levenick
Jim Levenick

Seems to me, even the notion of "invasive species" reveals a strange attitude; if people brought it (as opposed to birds, wind, or tides), it's "invasive" as opposed to "natural"?


The way I hear it, there were no people in the Americas 20,000 years ago (no pigs, no horses, no tomatoes, etc, etc…) -- how does one determine where to draw the (temporal) line that determines "native"?

Paul Jones
Paul Jones

There is a fundamental inconsistency in the ideas of ecology management.  Either:

humans are a unique species with greater power and therefore greater responsibility for stewardship over nature than all others,  such a notion as a creationist might have, or humans have simply the highest form of brain evolved tool use on earth, a product of natural evolutionary forces and therefore anything humans do is simple an act of nature on the ecosystem.  Are humans part of the natural ecosystem or stewards of the natural ecosystem? 


Andy Springer
Andy Springer

Humans are the #1 most invasive species, pretty darn hypocritical for us to think that we should have anything to say about other plants and animals.  Gotta love our current "god complex".

t. giobbi
t. giobbi

human activity has caused almost all the invasive species problems we read about. instead of killing off some species to save another we might want to start looking at the practices of global trade that lead to these concerns also.

David Alan McPartland
David Alan McPartland

I guess the white man would be considered an invasive species to the native American Indians we displaced ?

Millie Trees
Millie Trees

@C. Dufour Yes, that is a wise choice.The plants we call “weeds” are often favorites of pollinators because nectar and pollen haven’t been bred out of them to improve what humans call “beauty.”The herbicides being used to exterminate those “weeds” are also harmful to pollinators.We have very little knowledge of the extent of that harm because our pesticide regulation limits required testing on insects to only adult honeybees.

However, there is another equally important factor that is relevant to this discussion:  extreme forms of nativism are actively trying to eradicate honeybees because they are not native.  Some of the Nature Conservancy’s most extreme projects are eradicating honeybees.  This misguided strategy is based on the mistaken assumption that honeybees are competing with native bees to the detriment of the natives.  They are mistaken in that unfounded assumption, like so many of their assumptions.  Here is a report on a meta-analysis of 28 studies of the impact of honeybees on native bees which concludes that there is NO evidence of harm to native bees:  http://milliontrees.me/2013/09/03/niche-theory-is-there-room-for-everyone/

Millie Trees
Millie Trees

@John Measey I agree that the concept of “assisted migration” is fraught with ethical and practical dilemmas.I am opposed to the concept because I don’t think people claiming to be experts have demonstrated that they understand the complexity of ecosystems sufficiently to ensure that they won’t do more harm than good.Why should we put the fate of rare animals in their hands?

However, there is good reason to consider letting plants and animals remain where they were introduced intentionally or unintentionally, particularly when they are threatened with extinction in their historic native ranges.  Monterey pine is an example of a tree that has been planted outside its native range that is now threatened with extinction in its native range.  Ironically, the fossil record in California proves that Monterey pine was once more widely dispersed.  Yet, in places where Monterey pine existed in the distant past, it is being aggressively eradicated where it was planted by humans.  This is an example of the absurdity of choosing one narrow slice of time as the baseline for ecological “restorations.” 

Monterey pine has existed naturally throughout the coast of California during different periods of climate conditions.  It is now well adapted to many of those coastal locations where it grew naturally in the past.  Yet, because ecological “restorations” are attempting to recreate a landscape that existed in California in 1776, Monterey pine is being eradicated everywhere but its tiny native range in one county in California.  And in that historic range, the Monterey pine is dying out.

The nativist ideology is rampant with such absurd contradictions.  Ms. Marris is trying to sort through these contradictions to find an approach that is both realistic and appropriate to our rapidly changing environment.  

Millie Trees
Millie Trees

@Daniel Edrich There are similar projects going on all over California with similar unintended (maybe intended?) consequences.Here’s a project in a State park on the Sonoma coast where transporting dunes are killing the trees and encroaching on private property  .http://milliontrees.me/2013/12/31/coastal-trees-endangered-by-nativism/

But the winner of the booby prize for stupid projects doing the most damage is the spartina eradication project on the entire west coast, which is killing the few remaining endangered Clapper Rails.  The perpetrators of that crime know that’s happening, but they are sticking to their herbicide guns.  http://milliontrees.me/2014/06/02/spartina-eradication-herbicides-are-their-dirty-little-secret/

Bill Benfield
Bill Benfield

@Dave Richardson  In the pursuit of nativism, invasive species campaigners often ignore the effects of the eradication programme. In New Zealand, metabolic  toxins like 1080, which destroy all oxygen breathing life are spread aerially over the land, supposedly eradicating "pest" species only.

Nothing could be further from the truth. These programmes advantage the fastest breeders - generally rats, and rare native species like mountain parrots are heading towards extinction - from the poisoning. Invasive biology is mantra driven, and writers such as the author above trace it back to Charles Elston. In fact the roots are deeper and darker - http://ecofascism.com/review36.html

A sane approach is required that has to come to terms with the world we are.

Millie Trees
Millie Trees

@Dave Richardson OK, Dave.I’ve read your defense of your academic turf and I’m ready to offer you a deal.

First let me paraphrase your defense of your discipline.  Here’s what I hear you say:  “We know what native vs. non-native is when we see it, whether you do or not.  We may not know what harm non-natives are doing, but we’re sure they are doing harm even though we can’t prove that.  And even if they aren’t doing any harm, we’re sure they will all do a great deal of harm eventually.”

So, here’s the great deal I’m offering you and your colleagues in invasion biology—or invasion science if that’s what you prefer to call your academic turf.  By all means study non-native species to your heart’s content.  We won’t try to kill your discipline if you will just call off the practitioners of invasion biology.  Quit offering “scientific” cover to the butchers who are destroying our public lands.  Withdraw your support for the destruction of long-standing, diverse, healthy ecosystems whose only crime is that they contain non-native plants (such as Eucalyptus globulus which has lived in California for nearly 200 years).

Then peace will reign on the land.  

Nature Advocate
Nature Advocate

@Dave Richardson 

I take exception with something you stated, "For species that are already widespread, eradication is probably impossible, ..."

This is not the case of invasive-species house-cats. I eradicated hundreds of them from my lands by employing "Hunted-to-Extinction" methods (or in this case, "hunted-to-extirpation"). I've not seen even one cat in nearly FIVE years now due to the effective methods I invented and used. (You can read some of the most effective methods that I used posted here: americanhunter.org/blogs/arkansas-will-trap-feral-cats ) I estimate that about one-returning or one-never-seen-before native-species has been re/populating my lands PER DAY since every last invasive-species cat is gone. That's a LOT of species in five-years that cats had senselessly destroyed during their two-decades of infestation -- if not lost through predation than by starvation from cats senselessly torturing-to-death all the larger native predators' ONLY food-sources for cats' play-toys.

Hundreds of cats shot and buried in only two seasons of my time for less than the price of a couple cups of coffee for the ammo. (5,000 rounds of .22s on close-out sale for only $15 = 3 cats PER PENNY permanently GONE, sterilized, vaccinated against all diseases for which vaccines don't even exist yet, and even given a loving and permanent "forever home" 2 ft. under.) On rugged lands replete with dense foliage and doing so in only 2 seasons of my time. Whereas before these invasive-species disease-ridden vermin had been annihilating all the native wildlife on my lands for two decades, with no other resolve in sight by listening to any cat-advocates' advice and values, those who create and perpetuate the problem.

Eradication of any widespread endemic invasive-species is not only possible but easily attainable -- if you use the proper methods, dependent on each species. You just have to grow a spine and crawl out of your mommy's basements and face reality to do what actually works. Being a good steward of the planet doesn't just entail eating kale from your local "greenies" bliss-ninny's co-op. Hunted-to-extinction works on nearly all larger animal species -- especially these man-made house-cats that breed 2-4X's faster than any native cat-species. NO trapping method in the world can catch up to let-alone surpass their breeding rates and the rates at which criminally negligent cat-advocates let more be born and dumped outdoors, not to mention cats' abilities to out-adapt to any trapping methods invented. (Hint: there's a reason that the well-known phrase worldwide is not "trapped to extinction".) But hunted-to-extinction certainly works on them. I most certainly proved it where I live. Now prove it where you live. You'll be surprised how fast and effective it is.

Millie Trees
Millie Trees

@Dave Richardson That all sounds great, Dave.Unfortunately it has almost nothing to do with what’s actually happening on the ground.The precautionary principle certainly isn’t being used when herbicides are sprayed on fruit that is eaten by birds and other animals.The consequences of huge trees storing millions of tons of carbon aren’t being taken into consideration when those trees are destroyed.

What you are thinking in your ivory tower is not relevant to what is happening in our public lands.  Come take a look at some of the devastated landscapes where everything has been destroyed by prescribed burns, herbicides, and mechanical removal methods.  Come stand behind the fences to look at the non-native weeds that now occupy these empty spaces.  Then tell me about how cautious you are about your theories.

Here is just one small example of these destructive projects:  http://milliontrees.me/2014/07/07/relentless-war-on-eucalyptus/

John Fischer
John Fischer

@Benjamin Vogt I think we have learned to farm far more intelligently, but for farmers brought up in this environment of "get mine while I can" it does not matter. And it will not matter until farmers of all kinds are forced into responsible practices either through legislation or market forces. Since I do not see politicians weaning themselves from Big Ag's pockets any time soon, and with the general population refusing or unable to comprehend what is at stake,  I believe another, much more catastrophic dust bowl is looming in some form or another. 

In the mid west, many corn and soy growers are not bothering to rotate crops any more due to GMO modifications providing for greater inherent resistance to pests and herbicides. Of course, the weeds have evolved to meet this change and now farmers are spraying greater and greater amounts of roundup to fend off the resistant weeds. I imagine the same is true of the pests. And the well known cycle repeats.

In California's central valley, the ground is subsiding so much due to ever deeper water extraction by growers that homeowners' wells are literally being crushed. In some areas the water table has been drawn down 200 feet. HALF of that in the last two years due to drought. Once collapsed, the ground does not expand again if an attempt were made to replace that water. The water-holding capacity of the land is lost.

Combine the growers' irresponsible practices with those of the meat and fish industries and Soylent Green does not sound so far-fetched.

We know better. We also know that the food industry as a whole is not any kind of steward of the land. Between genetic modifications and irresponsible practices on a breathtaking scale, the entire food industry is setting the world up for an apocalyptic future, even without the atom playing a part.




Millie Trees
Millie Trees

@Benjamin Vogt If native plant advocates would look at the “deeper issues” as you suggest, they would not be destroying huge trees storing millions of tons of carbon that will be released into the atmosphere as carbon dioxide or dousing our public lands in toxic herbicides or setting polluting fires in grassland to prevent natural succession.


Those who are opposed to these destructive projects are looking at the deeper issues and what we see is that much more harm is being done to our environment with little long term benefit.  


Native plant advocates are mistaken that the existing landscape is in any way inferior to its historical predecessor.  Furthermore, the environment has been fundamentally altered such that it is no longer physically possible to return to that historical landscape.

John Fischer
John Fischer

@Jake Williams I think you completely miss the point. The health of humanity goes hand in hand with the diversity of our species. This is becoming clearer and clearer even in seemingly unrelated studies. Even, or especially, within the individual micro-environments of our guts, it is becoming evident that diversity is a key to overall health, and possibly THE key. It is now thought by many (most, almost all?) that low level systemic inflammation is the root cause to many of our modern-day diseases. In turn it is becoming more and more evident that this inflammation is directly related to the increasing homogeneity of our intestinal micro-fauna and -flora and everything in between. It seems obvious to me that diversity equals health in all ecosystems. Since no ecosystem is independent of any other, the healthier (more diverse) each ecosystem is, the healthier humanity is. Humanity needs diversity, simply for diversity's sake! Plus diversity makes life so much more interesting. I would get tired of eating black angus steak, roma tomatoes and ice berg lettuce every day, wouldn't you?

John Fischer
John Fischer

@Chrissie Raffensperger Nature has actually set some pretty sensible guidelines for development, and before PACs, it seems most communities followed them. Don't develop on top of mountains, on or in front of steep slopes, on or near earthquake faults, or near water ways.

Unfortunately for the entire world and humanity, developer money became savvy, legal ways of taking and making bribes were enacted, and now very, very active fault lines are covered with developments, steep slopes slip every year with catastrophic results, waterways are encased in tunnels or near-tunnels of concrete, etc. Mountain top development just ruins the view for everyone. 

Imagine if we treated each one of nature's deterrents as opportunities; wide green belts on either side of fault lines and water ways (no matter how small) and arks and wilderness on the mountain tops and hill sides. And what if we connected the parks and the green belts together. And installed paths and bike ways. And in-filled all available land before we expanded our city borders.

The horrible result as I see it? Migratory paths for wildlife. Greatly reduced car dependency with safe, attractive, and even exhilarating bike ways and walk ways, a vastly healthier environment, greater awareness of our world and our part in it, and most importantly, proper example-setting by officials of just how important our environment is to all of us. 

John Huscio
John Huscio

@Kirk Mantay cowbirds are native to the new world.........there are European cuckoos that are the ecological counterparts of north american cowbirds, but no actual cowbirds there...,,

Marc Archambault
Marc Archambault

@Tom Stohlgren 
Note that in many publications the headline is not written by the author of the article, but by the editor or a headline writer and its goal is to grab attention, which is why they often use loaded words. NG is not a peer reviewed science journal.

It's fine to take issue with the headline itself - and definitely to teach students to view them with caution, but headlines, like book covers, should not be assumed to be a reflection of the author's thought.

Though you have many salient points, you seem to have missed what I understood to be the central premise of the article. Namely that there is a problem with the dogmatic all-or-nothing attitude exemplified by the "substantial number of [ecologists who] said they would immediately eradicate a hypothetical non-native forest plant, even if it were shown to have no effect on the forest."

Kirk Mantay
Kirk Mantay

@Dan Alger Zebra mussels have claimed over a dozen specie of native mussels, and have fundamentally changed the chemistry and microbiology of the Great Lakes.   This information is easy to find.  

Dwayne LaGrou
Dwayne LaGrou

I just happen to live in Michigan, And the Zebra mussels are extremely dangerous. The reason is not about the stupid pipes, That is just a pain in the rear. The real problem is that they are filter feeders and they are filtering the water so much that there is no longer enough plankton for the fry to feed on and a growing number of t he native fish are declining in numbers because of the mussels. The Great Lakes has a multi million dollar fish economy that has suffered badly because of two VERY INVASIVE Species. The Zebra mussel is just the first, The second is the Sea Lamprey. They can attach to the adult fish and basically suck them dry through a hole in their side. Many fishermen are catching fish with huge scars and near death because of the Lamprey. So are all invasive species bad? No, But are some bad? YES, they can be devastating to some areas. And now we are battling an even BIGGER PROBLEM, The Asian Carp. You have seen the videos of them jumping out of the water. They grow extremely fast and prey on the small fry and the vegetation that they rely on. So the Great Lakes are on the front lines of Invasive Species. Some of these species are harmless while others can decimate an entire ecosystem!!!

Kirk Mantay
Kirk Mantay

@Jim Levenick An interesting and good point, Jim.  On the east coast, we have two bird species, Glossy Ibis and Cattle Egret, that "appear" to have invaded on the winds of hurricanes in the 1800s (around the time many invasive plants were being introduced via shipping).     What do we call these birds?

Kirk Mantay
Kirk Mantay

@Andy Springer   Right.  So obviously, given your hatred of this hypocrisy, you do not consume food that was grown on a farm, you do not hunt or fish, and you do not mow or maintain a lawn.   You also don't live in a structure (that was built on prior wildlife habitat) or use a vehicle on roads that were built on wildlife habitat.  Because then you would have a "god complex" about making decisions about other plants and animals.  Right?  You're a vagabond seed-gatherer, right?  Because otherwise, it would be pretty darn hypocritical.

Kirk Mantay
Kirk Mantay

@t. giobbi Yes!  But that would take foresight (and spending money on problems we can't "see" yet) instead of blind reactionary policies.

Kirk Mantay
Kirk Mantay

@David Alan McPartland And in some cases, they were the second or third "peopling" of parts of North America....themselves displacing other peoples who were there before them. 

Kirk Mantay
Kirk Mantay

@Marc Archambault @Tom Stohlgren  At some point during this author's project, the "premise" certainly was as you describe it.  Which is why the editor should have dumped the final result in the garbage.  Discussing dogmatics on this topic is very important.  However the execution of this article doesn't really achieve that.  In any way, instead resorting to "Meanie Animal Killers vs. awwww cute turtles."

Dwayne LaGrou
Dwayne LaGrou

Thank You Kirk M. I couldn't have said it any better!

D.L.

garen kessel
garen kessel

@Kirk Mantay @Andy Springer Hey Kirk. How does stating the hypocrisy of a situation equate to hatred? Personally, I still support preservation, but the idea that we can stop species from migrating and the idea that we can prevent evolution from occurring is absurd. Perhaps we can speed up or slow down the process, but survival of the fittest is inevitable and is the natural, normal outcome. Extinctions have been occurring on this planet since long before humankind entered the picture and will continue long after we are gone. Some people seem to think that our Eco-system was meant to be permanent. But the truth is nothing is permanent, change is constant and nature is as cruel as she is beautiful.

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