Last year, I posted an argument that not all alien species are bad, based on a study of the invasive aquatic plant Hydrilla; I got pretty bloodied, not only because it's an unpopular notion in enviro circles, but also because of my clumsy presentation and defense of the idea. Yesterday's New York Times ran a feature called "Friendly Invaders" that says rather well what I was angling on, and then it goes a lot further. The scientists profiled make the case that very few actual extinctions can be traced to invasives, some introduced species like honeybees are crucially important in their new homelands, and introductions usually just increase the overall biodiversity of their new homes. Islands are where that all goes south, of course, and some invasives are clearly awful, but overall, I find it pretty darn interesting. You?
Alien invaders: More to the story, part 2
NYT critiques alien biology 27
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Posted 1:09 PM on 10 Sep 2008
by Erik Hoffner -
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Erik Hoffner is the coordinator of the Orion Grassroots Network which supports the work of hundreds of grassroots groups and which connects the green leaders of tomorrow with good work today via the Grassroots Jobsource. Based in Massachusetts, he is also a freelance photographer.
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mihan Posted 7:39 am
10 Sep 2008
The larger question might involve changing the ecosystem rather than actual extinctions. Isn't it still bad if an introduced species (like worms used for bait in the upper midwest) causes the ecosystem to change drastically?
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Bart Anderson Posted 7:59 am
10 Sep 2008
There is a strong anti-invasive stance, as you note, among most enviros.
On the other hand, there are counter-movements, for example in permaculture, that either embrace or are less hostile to new species.
I would like to see a greater depth of understanding.
We come from a culture that is biologically and ecologically retarded. As a result we demand simple black-and-white answers.
The mark of good biologists, in my view, is that they begin their comments with the phrase: "It depends..."
A few years ago, I collected links for some good articles on the subject, if anyone wants to learn more:
http://www.cwo.com/~bart/invasive.htm
Bart
Energy Bulletin
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atreyger Posted 8:00 am
10 Sep 2008
That's an example of what I mean (although the article does not question invasives). Basically, if you had an influential professor (typically, although it could be another person) continue to tell you that invasives are bad, they're bad.
If, on the other hand, you were taught that purple loosestrife accents a garden that you are landscaping, it is good.
Plus, and this is important: invasives are very common, particularly in the ecosystems that I know. The difference is in whether they are native: 'good' if you are a staunch environmentalIST, or an ecologist with a strong environmentalIST leaning, or 'bad' if you are a vegetation/forest/ecosystem manager, particularly if it is not of any monetary/aesthetic/etc. value in the specific situation.
From an ecological perspective, a native invader does similar things to the ecosystem that a non-native does. Oftentimes, the difference is in the ability of native consumers to quite literally learn to forage the non-native invader.
In terms of species extinction, I agree with the recent article, in that typically the invaders outcompete in a very common or an underutilized habitat, while peripheral habitats are safe.
For example, the Phragmites and loosestrife are replacing cattails, which themselves are invaders. The damage is there, in that cattails are a known food source for muskrats and beavers, etc. However, they are not a food source for honeybees (like loosestrife), and since the introduction of the biological control agent several years back, the loosestrife and the bee populations have collapsed at the same time in the northeastern US. Now, I am not sure if anyone has pursued that line of research, but it might be worthy of consideration.
Both Phragmites and loosestrife are much better at taking up the increased nutrient pollution caused by humans, something at which cattails are very poor. So, the invasion and nutrient pollution go hand in hand, in both being human-caused and problem-solving for humans.
Another quick example: I 'moonlight' with a Eurasian milfoil eradication project, which paid well and was a good experience. However, when in the water a different picture emerges: crayfish and as a result of that predatory fish, as well as juvenile fish love the stuff. After milfoil is gone, there is just literally no cover (and VERYlittle in the native underwater vegetation), and thus the food web (starting at crayfish) collapses to a minute level.
I could keep going, but the main issue in many ecologists' arguments is this: if biodiversity is good, and biodiversity is increased by exotics and to some extent 'moderate' invasives (as opposed to 'super-invasives'), then why would we want to eradicate the invasives?
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Erik Hoffner Posted 8:47 am
10 Sep 2008
mihan, I agree about the worms. Or knotweed, asian longhorned beetles. Chestnut blight! There are some newcomers or changes that I can't abide the thought of.
But Bart, I agree very much, and found the article's subject's final quote to be very useful:
"It's not that this is all good or all bad, and I'm not sure science should be the arbiter," Dr. Brown said. "Placing values on these things is the job of society as a whole."
I couldn't agree more. This needs to be a wider discussion.
Erik
The Orion Grassroots Network: supporting grassroots groups working for conservation, justice, & more
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wiscidea Posted 8:57 am
10 Sep 2008
I've commented on this story over in the "In the News" section and I can assure you I'll have a lot to say about it here. You know how I feel regarding invasive species.
I'd like to zero in one what item for now, just to see what others have to say about it...
Erik wrote...
"...some introduced species like honeybees are crucially important in their new homelands..."
Correct. Honeybees are crucially important for agriculture. And we are facing serious problems, as a species, if honeybees disappear due to a combination of poor management practices, newly introduced diseases that are catching up with them, pollution, industrial agricultural practices, et cetera. I'm very concerned about this issue.
However, are European honeybees crucially important for conservation of native plants or an additional threat to those plants? Do they displace native pollinators? Were diseases that affect related native species brought over with the honeybees? Is it wise to rely on a single species to pollinate so many of our crops?
I don't know the answers to these questions.
Here's a tentative OPINION... I'm not convinced that the introduction of honeybees to North America was such a grand idea. We are now dependent on monocultures of insects to pollinate our monocultures of plants. And the honeybee has been an enabler of sorts. Because of the work done by the European honeybees, our modern agricultural system has encountered NO DETRIMENTAL FEEDBACK as it completely destroys populations of native plants that sustain native pollinators. It has has encountered NO DETRIMENTAL FEEDBACK as it sprays chemicals over and around fields, killing native pollinators and, indirectly, plants dependent on those pollinators. The honeybees were always there, masking the some of the harm inflicted by poor agricultural practices.
And now we see the consequences... the native pollinators are declining, their habitat is declining, a lot of it is GONE. And the honeybees we introduced are now disappearing. So, the consequences of introducing honeybees might not be so positive.
We might have been better off if the farmers of North America had relied on native pollinators and adapted to them, better off if strips of wild native plants had been maintained over the centuries to ensure adequate pollination of our food crops. We'd be better off learning to live with our local flora and fauna rather than risk introducing an exotic organism that might behave in unexpected ways once released.
(Hmmm... I almost sound like a person criticizing GMOs.)
Just my opinion.
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Delay And Deny Posted 9:30 am
10 Sep 2008
I was just reading "Reinventing the Sacred" a diatribe against the Reductionist viewpoint in science (saying that some complicated process like Creativity is "just" the physics of atomic particles).
Anyway he gives a fantastic survey of contemporary science in many fields (autor is a Professor of Complexity).
Thinking this way, I'd have to say with invasive species...it's not so simple.
For example, there is something called a Climax Ecology. That means that the species are highly adapted to their niches and even small changes can dislodge them...a specific food, temperature range and so on. On the other hand, adjacent possible, which is a general concept of autocatalysis that results in the next set of complicated structures being generated from the current building blocks...this is why life went from a few organic molecules to millions.
Anyway, so yes, subtle changes will probably eradicate climax species...but there is pressure to fill every new niche. An invader could damage a climax niche, or fill and empty one. Or it could interact in some type of symbiosis and add a niche.
The question for humans is how adapted and adaptable are we? Are we so specialized that the exact conditions as they were in 1820 are those that are ideal for us? Or are we changing with the circumstances...
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Craig Allen Posted 11:29 am
10 Sep 2008
Foxes, cats and rats have eliminated small to medium sized ground mammals from much of the mainland. Reintroduction programs invariably fail if expensive feral control programs are not maintained indefinately. This prohibits reintroductions to extensive areas and therefore a large proportion of our precious small marsupials and native rats and mice are now restricted to small islands and fenced reserves.
Rabbits have decimated vegetation across the continent. When calicivirus was released over a decade ago we saw the return of wildflowers to vast areas of the country where they had not been seen for many decades. However, species with short lived seeds wereless capable of doing som and now the rabbits are returning.
I'm have worked in vegetation conservation and management positions for many years, including on projects to save heathlands, woods, forests and wetlands from the encroachment of weeds. It is very difficult to do because weeds are so tenacious. Throughout the bulk of the landscape it will never be done as it is such a labor-intensive task.
Weeds are spreading at an astounding rate. Wherever I go I see roadside and other remnants of our beautiful bushland being invaded and degraded. Over time you see the proportion of introduced grasses and other weeds increase until eventually all the native wildflowers, grasses, lichens, and small shrubs are choked out. It is very disheartening. Especially when as a final straw a farmer or council worker comes along with a boom spray to herbicide the entire patch, thereby killing everything and ensuring that the following yaear and thereafter there are no natives and just weeds.
We are seeing huge damage caused by government funded programs to control agriculturally damaging weeds that also invade native ecosystems. For example, we are losing the last few patches of native wildflower-grasslands when they are invaded by a weed called serrated tussock. Herbide is used to eliminate this, but also destroys the hundreds of other grasses and wildflowers found in such places. The loss of wildflower-grassland remnants on roadside and railway sideing in this way in my region is now almost complete. The same thing is happening in woodlands where european gorse is invading.
When native vegetation is lost, most of the native insects and other invertebrates are of course eliminated also. And also many of the lizards and small mammals also, including pygmy possums, bandicoots, dunarts, plantigales, antichinus, native mice etc.
And now to top it all of, we have a soil-borne disease called phytophthora, which is spreading through our national parks and other areas, often along recreational and fire control tracks. It kills 50% or more of the understory species and many trees, causing grasses (most of which are introduced) to take over, and eliminating food sources for mammals and birds.
I'd argue that anyone who thinks that introduced pests and weeds are not a problem, must have very little expreience observing or working with native ecosystems and doesn't have the capacity to see or appreciate the difference between a weed infested mess and an intact ecosystem.
Find yourself an ecologist or field naturalist and go for a drive so they can show you the landscape through their more knowledgeable and appreciative eyes.
Yes, ecosystems dominated by weeds and pests are still valuable for some species, but they are sad depauporate shadows of the intact native ecosystems they displace.
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Tasermons Partner Posted 3:15 pm
10 Sep 2008
...and 30 years later, it overran the plains.
And the birds were silent.
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Wolverine Posted 5:42 pm
10 Sep 2008
As I said in another thread on this subject, the assertion of this blog seems to be promoted by some industry that's keen on global trade but has been getting flack due to all the harm non-natives have caused. Perhaps the exotic plant industry? Either these "scientists" have been bought off or they're totally myopic, reductionist, and ecologically ignorant.
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MAD MAC Posted 8:42 pm
10 Sep 2008
Victory in Pattani
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wiscidea Posted 11:55 pm
10 Sep 2008
Now that I actually read the NYT article...
It is a poorly written article for essentially one reason. The title "Friendly Invaders" and much of the article suggests -- suggests -- that the new research shows invasive species are not the problem scientists thought they were. However, from the title to the end of the article, the terms "invader", "invasive", and "exotic" are used interchangeably, allowing one side to say most exotic plants are not a problem and the other to counter that invasives, including animals, are a problem. There are two different phenomena being woven together to create an artificial debate... that is, implying even scientist disagree on this issue... sound familiar?
The original paper the article is based on appears -- and I admit I have to read the PNAS paper to determine whether my assessment is accurate -- appears to simply say that competition from the vast majority of exotic plants, which technically range from innocent tulip bulbs to aggressive kudzu, does not lead to extinction of native plant via competition. This is all. No more. In fact, it looks like the authors point out the predation by exotic predators IS a major problem. And it does not look like they thoroughly examined other ways exotic plants might displace native plants.
Considering some specific points in the NYT article, though the fuzzy definitions of terms be used really make the NYT article pretty much pointless...
Exotics have displaced only three native New Zealand plants:
Which ones? Were they keystone species? How many native invertebrates and vertebrate were dependent on those plants? What if a wimpy exotic plant that exuded a toxin that killed only Redwood trees invaded California. Would we celebrate the increase in biodiversity along the west coast? Would it be a net gain?
A scientist epxresses his dislike of the phrase "exotics are evil":
Sure. He's correct. For the most part, exotics are perfectly benign... as far as we know. One might argue that corn and soybeans -- not invasive on their own -- displaced 90-99% of an entire North American ecosystem. Most exotics appear benign. Would this same scientist, or any rational ecologist, express dislike of the phrase "invasives are evil"? The article should use consistent language to frame this debate.
Speed and stress:
If enough people read far enough. Competition between exotics and natives isn't really a problem, except when plants are moved rapidly and over long distances, combined with other threats to native plants. Ummmm... perhaps I wouldn't view exotics as potential problems if we (1) had not destroyed 90-99% of North America's grassland, (2) were not planting new exotics right next to threatend ecosystems, and (3) restored the natural fires that maintained North American ecosystems.
Competition from exotics shows little sign of causing extinction:
What about other effects? White sweet clover might not compete directly with a native plant. Sure. It occupies a bare spot of ground. But then it changes the local microenvironment and soil ecology. It creates dense shade that blocks germination of native plants. It is less combustible, so interferes with the progression of natural and prescribed fire. It adds nitrogen to the soil, which creates an environment that favors other exotics -- some invasive -- over native plants. The sweet clover alters the cover available for grassland birs. It might draw pollinators away from native flowers, preventing good seed set. There is a whole cascade of consequences beyond direct competition. And this is just one plant.
Native species might be pushed from most of their habitat, but find homes in other refuges, so don't worry:
Oy! What about other elements of that habitat that might have been dependent on the native plant? And how large are the refuges? Are they connected, or do we end up with isolated islands that cannot sustain genetic diversity? And is there an effort to protect those few islands from development or other threats?
TO BE CONTINUED...
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C4nier Posted 12:42 am
11 Sep 2008
My work currently is centered on invasive species information management and so I've seen floods of responses to this article over the last couple of days on the invasives community listservs. These invasive species professionals have sophisticated critiques of the article (not all are against it) but I'll point out a couple of things that really bugged me.
They use full extinction as their only measure of whether the impacts of invasive species are negative, and they are looking only at plants. These species are entering complex webs of interacting populations and communities that stretch all the way down to soil microbes, which can be the difference between life and death for a community, but aren't readily observed or studied. Disruption may not be seen immediately and extinction may not happen overnight (or be "observed"), and perhaps may not be exclusively caused by the introduction of a new species. But it's one more barrier for native species to overcome in their struggle to continue to exist. In the end, if natives continue to exist for now, but at a fraction of their former population size, is that good enough? I would say that a diminished population size of any species is going to impact other species in that community in some way.
As for introduced species adding to biodiversity, I think this is a simplistic view of the world. As I said, I work with invasive species information. If you peruse the databases on invasive species from around the world you will see that the same group of repeat offenders taking over New Zealand are also taking over Chile, Argentina, and South Africa - with a few exceptions and a little variation. But my point is that although you are technically increasing the number of species found in a location, as long as natives do not go fully extinct, you are impoverishing the landscape globally because by number of individuals or biomass - however you measure it - these same 150 or so invasive species eventually make up the bulk of the landscape. And I don't know about you, but I never walk through a thoroughly disturbed area with lots of introduced species and feel like I am in any kind of exceptionally biodiverse place. I just think it's a pity that all landscapes in this particular bioclime are starting to look alike.
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Sharon Astyk Posted 12:50 am
11 Sep 2008
Sharon, eating her invasive edibles for lunch ;-)
Sharon, with dirt under her fingernails.
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wiscidea Posted 1:18 am
11 Sep 2008
It originated in Mesoamerica and was carried north and spread by humans. This makes it an "exotic" plant in North America. Not all exotics are from continents on the other side of an ocean.
There is a plant from the desert southwest of North America -- I don't recall the name -- being sold as a soil-building cover crop for other regions. It is an exotic plant in the midwest. Some ecologists consider it invasive. Others disagree. But should a company distribute it before we determine whether it will harm ecosystems? Once it is sown, it will be difficult to get rid of.
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atreyger Posted 1:24 am
11 Sep 2008
On the other hand, we have picoallen, who seems to have worked quite a bit in the field. However, the analysis seems to focus away from the original article, and dubiously begins with foxes, rabbits and canetoads. The next argument is that you cannot use herbicides to control the invasives. One issue with that is, basically that unless Australia puts its entire GDP into handweeding out the invasive weeds, the results are going to be abysmal. So, it appears that picoallen, while passionate, has missed the mark.
Wiscidea brings up some good but emotional points, not necessarily looking to consider the issue as is, but rather how it should be. That may be a good way to approach philosophical endeavors, but vegetation management is a different endeavor. Furthermore, it appears that he uses questions more than answers: white clover, honeybees, etc., with lots of what ifs, but few as is's.
C4Nier,
You are correct that there are other, not readily observable effects. But, the idea that in 250 years (is that right?) only 3 plant species have disappeared in NZ, counteracts this argument. Now, granted that there are actual and 'effective' extinctions, but then what metric would YOU use to determine what an 'effective' extinction is?
Also, 'biodiversity' is a very slippery subject. Are you talking about alpha, beta, gamma, epsilon, or delta diversity? That is are you talking about a single community, between two communities, landscape, broad geographic region, or between communities between geographic regions? While it may not feel diverse when you walk in one invaded community, you are right for alpha, but may be way off for beta, gamma, or epsilon.
What I find interesting is that no one up to now has attempted to consider the effects of native invaders.
Once, again, training. (Hulk voice) Native good, non-native bad.
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atreyger Posted 1:42 am
11 Sep 2008
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wiscidea Posted 1:45 am
11 Sep 2008
I must admit my opinions largely swirl around my 10-year effort to eliminate the white and yellow sweet clover, exotic thistles, exotic honeysuckle, crown vetch, buckthorn, and wild parsnip from a 2-acre remnant of Wisconsin short-grass prairie vs. looking at this issue as a trained ecologist. It has required an enormous amount of personal physical labor and thousands of dollars for professional assistance (guidance, prescribed burns, mowing, purchasing seed).
Thus it is somewhat an emotional issue for me when someone says... don't worry.
I've seen and confronted -- quite directly -- the results of invasive exotic plants. And I've helped others deal with the consequences of invasive exotic plants. If the Precautionary Principle applies anywhere, it certainly applies to exotic plants. It is difficult to reserve the decision to transfer a plant from one region of the globe to another.
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wiscidea Posted 1:52 am
11 Sep 2008
"It is difficult to REVERSE the decision to transfer a plant from one region of the globe to another."
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wiscidea Posted 2:06 am
11 Sep 2008
"What I find interesting is that no one up to now has attempted to consider the effects of native invaders."
Here or in general? I've resisted here because I view it as a slightly different topic.
There are, of course, native plants invading grassland communities due to the suppression of fire. I'm sure there are similar problems for other ecosystems.
This is a serious issue... suppressing and altering natural forces and cycles... suppressing fire, altering stream flow, building dams, preventing deposition of silt on flood plains... and another threat to biodiversity.
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atreyger Posted 4:13 am
11 Sep 2008
However, invasives are in the public eye, and as such there will be a majority opinion on it (in this case, 'bad'). It is rare to hear the moderating voice within the chorus of 'bad, bad, bad', and that is why I like the above study and that is why I am taking the time out to write about it.
Basically, I am taking a step away from my ecological training (with environmentalIST overtones), and going towards my vegetation management side with a more rational scientific (and unbiased) approach. If anything, I am promoting an invasive spp. 'triage' solution if you will. Attempt to eliminate the 'super-invasives' (although you will never succeed), leave the sporadic invasives and exotics (unless you know them to be a problem elsewhere), and leave the rare non-invasive species alone. I think that there already is a very good system in place for attempting to do the above (I guess I'm sort of pro status quo, then), since resources are limited, and managers realize this.
Also, it will be impossible to get rid of the 'super-invasives', the best we can do is relegate them to a background level.
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wiscidea Posted 4:51 am
11 Sep 2008
My primary objection to the NYT article and the Grist posts (both of them) is the lack of distinction between invader, exotic, and invasive. The NYT article is the sort of thing someone opposed to controlling the spread of invasive plants could latch onto and say.. "see, even scientist disagree over whether invasive plants are a problem... cut funding for programs to preserve habitat and control invasive plants until they figure it all out... those crazy academics are always flip-flopping."
The subject of the PNAS paper (I think), the title of the NYT article, the content of the NYT article, and the discussion here is a messy amalgamation of several different topics... yet they are presented as opposing views.
It looks like the original paper really just says that of the thousands of plants introduced to New Zealand, only a few are a problem and three native plants were driven to extinction by competition. This does not sound like news or a contradiction of previous views. And it does not say there aren't other ways exotic plants might have led to the extinction of native plants or other organisms.
Only a few exotics plants, due to their aggressive growth, are obvious threats to the prairie remnant I mentioned. I plant plenty of exotic fruits and vegis around my home and I'm not worried that they will become a problem. But I often wonder what other exotic plants are doing to change the local ecology. Is that patch of red clover adding nitrogen to the soil and paving the way for a new invasion? Is the queen-anne's lace attracting pollinators that would normally visit the blazing star right now? I think these question -- yes, I have a lot of them -- should be addressed before folks go around saying "invaders" are not necessarily bad. Or someone should a least explain to the public the difference between invader, exotic, and invasive.
The NYT article SUGGESTS that the paper says more and that perhaps we don't have to worry about most exotics. However, we simply don't know and cannot evaluate which exotic will become the next problem.
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wiscidea Posted 2:25 pm
11 Sep 2008
[Sorry... I have to finish my critique of the NYT article.]
Regarding the hybridization of cordgrass in England and the evolution of diversity:
The comment by the scientists regarding the hybridization of North American saltmarsh cordgrass and the English small cordgrass would be more persuasive if Carl Zimmer added some detail. First of all, hybridization does not necessarily equal evolution of diversity. Two gene pools have been merged, not necessarily creating genetic diversity. Yes, there is a new species and it can now diverge from each parent species. But what niche does it occupy? Is it displacing one or both of the parents? If it is displacing one or both parents, does the population contain all of the alleles of the two parent species Is the new hybrid more vigorous than either parent and competing with other species? There are a lot of questions and I think it as dangerous - if not more dangerous - to assume everything is fine than to assume there is a potential problem. Mixing everything up and letting God sort it out is not a very scientific approach to caring for our environment.
Regarding the fact that a third of existing plant species are products of hybridization, effective isolation of the breeding population, and subsequent evolution:
Correct. But this does not justify combining flora and fauna from different continents far faster and on a larger scale than any natural force other than humans can accomplish. The Earth has also been 10 degrees C warmer... so don't worry about climate change? The Earth has also been 10 degrees C cooler... so go ahead and pump sulfur dioxide into the atmosphere? Asteroids have collided and wiped out vast areas of life... so don't worry if a loose nuke goes off somewhere?
Regarding the notion that natives are likely to adapt:
Evidence for how common this is? What about the native species that don't adapt and all of the species connected to them? Please see my comments regarding birds nesting in honeysuckle and the butterfly that lays its eggs on the exotic milkweed following Erik's earlier post. I'm not arguing from a purely emotional perspective and just asking a lot of questions. There are clear examples of species harmed by exotic plants that seem otherwise benign. Certainly, random change and natural selection will preserve native species to some extent. BUT... given the loss of habitat, declining populations, threats from pollution and relatively rapidly changing weather patterns, and the rate of introductions of exotic organisms as humans move them about, it is very wrong to assume that species will have sufficient genetic diversity and time to adapt as they have in the past.
Regarding species have invaded new habitats when continents collided:
Please see above... we are essentially bringing continents together faster than any other natural force, the expanse of habitat for species to move around in was once much greater, populations were once much greater, and there was more time for adaptation. We live in a different world... sorry to state the obvious.
As I suggested earlier... if the Precautionary Principle applies to anything, it surely applies to moving various species from one region to another. We don't even have a reliable inventory of the actual biodiversity out there. Can anyone say that the movement of a plant from one continent to another hasn't wiped out an important fungus or bacterium? There's now concern that neem tree plantations in South America are altering the local soil chemistry. If a plant like the neem tree - a single species - escapes cultivation and becomes an invasive plant, it could decimate an ecosystem.
And what if an exotic plant brings an exotic disease with it? What if, after thousands of exotic plants have been introduced to North America, only one native plant, the American Chestnut, was pushed to the edge of extinction? Would we say, don't worry about invaders? Hey... only the dominant species of a major ecosystem was pushed to the edge of extinction.
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wiscidea Posted 2:43 pm
11 Sep 2008
If I learned one thing in the single journalism class I took, it is that you want to arrange an article so the most important information that you want to communicate is at the top of the article, starting with the headline. Why? As readers go through the article, they start to lose interest and more and more are lost as the readers progress from top to bottom. Very few people apparently continue reading right to the final sentence.
Carl Zimmer presents one side's view -- don't worry about invaders , this happens all the time in nature -- at the top of the article. He presents the other side's view -- there are some very serious exceptions and the world is different -- only after about 3/4 of the way through the article. The take-home message for most readers will be "don't worry".
I might agree with wolverine. This looks like a pro-exotic plant industry propaganda piece. If not, Carl Zimmer is at least guilty of sensationalism and distorting scientific findings. Sad... doesn't he write for Discover Magazine? The NYT article is VERY poor science journalism.
Where are we going and why are we sitting in a hand basket?
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amazingdrx Posted 3:30 pm
11 Sep 2008
The migration of viruses and bacteria might just wipe out the human species?
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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atreyger Posted 3:18 am
12 Sep 2008
So wiscidea does seem to get away yet again from as is to what if (or maybe just what, where and why). Curiosity and 'thirst for knowledge' is a good thing.
But the real bounce is this: migrations and invasions are an integral part of nature and I would argue, with solid evidence, that these are the norm rather than an exception. Nature is VERY dynamic, static is not something that it does. So, to give a quick example: current plant species distribution (or rather the 'restorative norm') reflect 100+ years ago, rather than now! Now I don't know if that's true for every distribution, but it's certainly true for trees of the northeast. Just like Wiscidea said, 10 degrees up and 10 degrees down.
Currently the preponderance of eastern hemlock (a very long-lived species) in southern Appalachians is the result of the little ice age during the middle ages. Climate change already ensures that plants migrate or go extinct, with the resulting effects on the distributions and assemblages. It may be that we will see never before experienced assemblages of species, and most will (and will need to) become invaders. This is that rather important native vs. non-native distinction that I brought up earlier. Without the distinction, it's hard to have that oomph in the general invasives argument, since natives can be just as, if not more, invasive.
So, to get to some examples, buckeyes are not native to New York (specifically Syracuse), and probably the closest natural range specimen (thinking 50 years ago) of a buckeye is located maybe 400 miles away from here. There is a local seedling population of buckeyes (possibly horse chestnut, since seedlings tend to be weird with phenotypes, and since I didn't have the time to check the twigs) that is established in a local forest. This is most likely the result of plantings somewhere nearby, but in essence it doesn't matter, because it is a type of an evolutionary strategy. These are not native, and they are invading, so the distinction is starting to blur. Virginia creeper is another example of the same. I have variously seen ecologists and naturalists say Virginia creeper is 'good' or 'bad' because it is either 'native' or 'invasive'. In Virginia, both are right, in New York, only one, guess which one?
In short, it is easy to flail our arms and scream help in a black&white universe, but the reality and the distinction is blurred. Climate changes compounded with site availability are crucial to understanding past ranges, and are helpful to attempt the prediction of future ranges. But, in fact, if the current climate change continues at the current rate, we will NEED to start mass introductions of species.
I can foresee some people's argument: the examples above are from the same continent. True enough, but doesn't it strike you as odd that some species extend from Mexico or Central America all the way to Canada? Bracken fern is a great example. How about sycamores, hackberries, redbuds, etc? These are not trivial examples, since their establishment and range is a direct result of invasion. And how about the possum? This is a highly successful natural invader that hasn't existed in North America until the land bridge with South America. Or how about central America in general? This is one of the most diverse areas in the Americas, precisely because it has been invaded over and over again by spp. from both Americas.
So, even natural biodiversity is a result of invasions. There is another topic: genetic diversity and speciation. That Spartina anglicans example that was mentioned earlier is an interesting, but somewhat peripheral example. As an answer to wiscidea, it primarily invades un- or under-utilized beach front property as opposed to the other two species. However, the real topic with invasives is that over and over again, we see that it's only one genotype that becomes wildly successful. It might have something to do with hybrid vigor, maybe a secondary metabolite or large seeding rates. But the real interesting thing is that these are monocrops, and as soon as one predator evolves a biting part or its own secondary metabolite to overcome plant's defenses, the plant population is done. Same principle as monocrops in agricultural systems.
I might have other spur of the moment ideas, but I'll cut it short now. Mkay.
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josullivan58 Posted 3:52 am
12 Sep 2008
What to do about alien/introduced/invasive species involves not just science but also economics and ethics. The last line of the article:
"It's not that this is all good or all bad, and I'm not sure science should be the arbiter," Dr. Brown said. "Placing values on these things is the job of society as a whole."
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wiscidea Posted 9:43 am
17 Sep 2008
"I grew up thinking worms were everywhere! Perfectly normal and an indication of a healthy environment. Well... they apparently did not exist in glaciated portions of North America until humans accelerated the move north. And this is a problem because ecosystems do not have time to adapt. The plants and animals dominating northern forests are not used to having worms around...
http://www.nrri.umn.edu/worms/forest/index.html
Result? Worms rapidly consume organic matter. Northern forests contain trees and herbs dependent on a layer of organic matter for reproducing. The mature plants are still there, but they are not being replaced. All the insects, birds, reptiles, amphibians, mammals, bacteria, fungi, protozoa, et cetera dependent on those plants will eventually be gone. Entire ecosystems occupying a large part of our continent will no longer exists. Interestingly, the invading worms also reduce carbon sequestration! Ouch!"
Now I've learned that earthworms are causing other trouble...
http://www.wssa.net/WSSA/PressRoom/WSSA_Nightcrawers.htm
Earthworms are facilitating the spread of weeds!
So... one little exotic species is causing all sorts of havoc and paving the way for other invasive species. Welcome to the homogecene epoch.
Where am I going and why am I sitting in a hand basket?
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