Could invasive species' bad reputation be undeserved? Bucking conventional wisdom, new research suggests that if exotic species aren't predators of natives, competition by nonnative species can actually improve biodiversity. A recent study in the Proceedings of the National Academy of Sciences notes that just three of New Zealand's 2,065 native plants have gone extinct, despite introduction of 22,000 nonnatives. "The overall pattern almost always is that there's some net increase in diversity," says researcher James Brown. "That seems to be because these communities of species don't completely fill all the niches. The exotics can fit in there." Critics point out that historical movement by invasive species pales in comparison to the estimated 7,000 species now schlepped to a new place by humans every day. "If you pour on more species, you don't just increase the probability that one is going to arrive that's going to have a high impact," says researcher Anthony Riccardi. "You also get the possibility of some species that triggers a change in the rules of existence."
source: The New York Times
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Comments
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BobG Posted 1:27 pm
09 Sep 2008
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Whiskerfish Posted 5:17 pm
09 Sep 2008
This is an easy line to spin if you look at things at low resolution.
And ignore the fact that many native species have been saved from the invasive species onslaught by difficult and expensive conservation measures.
And, and, and.
The study is nonsense. Invasive species are, in general, a serious problem. Period.
Whiskerfish
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wiscidea Posted 4:57 am
10 Sep 2008
I don't know who is responsible -- the authors of the PNAS paper, The New York Times, or the Grist editors -- but someone is playing fast and loose with language here.
The term "invasive" is not synonymous with "exotic".
It is clear that invasive species are a problem. But this does not mean all exotic species are a problem. In fact, I'm not surprised that the vast majority of exotic species display little effect on native ecosystems. Throw a handful of crown vetch seeds on my prairie remnant and you'll see two acres of crown vetch and little else after about ten years. Throw a handful of soybeans out there, and you'll see zero impact.
"Bucking conventional wisdom, new research suggests that if exotic species aren't predators of natives, competition by nonnative species can actually improve biodiversity."
This doesn't buck conventional wisdom. Seems obvious... an exotic species that isn't a predator or dominates a niche is NOT INVASIVE. So, of course it adds the local biodiversity. Invasive species, by definition, displace native species.
"A recent study in the Proceedings of the National Academy of Sciences notes that just three of New Zealand's 2,065 native plants have gone extinct, despite introduction of 22,000 nonnatives."
Just three? What is those three plants are the sole source of food for a couple dozen insects, reptiles, birds, or mammals? And what if those insects, reptiles, birds, or mammals are necessary for the survival of other organisms? There is no such this as "just three" plants going extinct.
Furthermore, did they conduct a thorough enough inventory to demonstrate that the exotics -- whether invasive or not -- have not reduced the populations of native plants or affected other organisms? The introduction of an exotic plant can introduce new toxins. I believe there was an example of a butterfly preferring an exotic milkweed over native ones, but the exotic milkweed killed the larvae. Oooopps. But... hey... it was just one species... so I guess no one cares.
""The overall pattern almost always is that there's some net increase in diversity," says researcher James Brown. "That seems to be because these communities of species don't completely fill all the niches. The exotics can fit in there.""
The local biodiversity might increase. There is a net gain when you add a thousand exotics and eliminate only one local species, but the global biodviersity decreases. Just three species? Just three here and three there, and another three over there.... it adds up.
The critics are correct...
""If you pour on more species, you don't just increase the probability that one is going to arrive that's going to have a high impact," says researcher Anthony Riccardi. "You also get the possibility of some species that triggers a change in the rules of existence.""
Regarding the overall tone of this post and the New York Times article... it is a good demonstration of how anti-environment people spin science and use slippery language to justify ignoring serious problems. I would not be surprised if the New York Times or similar articles are used by Republicans to call for pulling the funds from programs designed to eradicate or contain invasive species... totally ignoring that the research simply shows most exotics are not a problem. Invasive plants are clearly a problem. And invasive predators are even worse.
Thumbs down for the Grist editor who chose the title...
"Could invasive species be a good thing?"
Invasive species... NO!
Exotics... maybe, maybe not. I like grapes as much as the next person and I'm not afraid to try growing a European variety.
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Wolverine Posted 6:57 am
10 Sep 2008
This post sounds like PR propaganda for global trade, as in don't worry, non-native plants are actually good for you. Yeah right, so is sodium di-poisonate.
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wiscidea Posted 11:53 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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wiscidea Posted 1:17 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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Wolverine Posted 2:51 am
11 Sep 2008
This is a perfect example of where the precautionary principle needs to be used. Because humans can never know all they need to know in order to prevent serious ecological harms from non-natives, the prudent course of action is to prevent non-natives from being propagated and moved around by humans as much as possible. (As Wisc said above, we also need to remove them and replace them with natives as much as possible, but that is a more advanced step in the process.)
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wiscidea Posted 2:28 pm
11 Sep 2008
http://gristmill.grist.org/story/2008/9/9/143032/1416#22
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Pinsularum Posted 3:10 am
20 Sep 2008
I'm working with one of the apple snails P.(omacea) insularum. Its a snail the size of an apple and is currently invading Houston, Florida, and some other places. It's not "a predator" it just eats plants. To give some idea to the damage things like this cause if we go to the closest relative we know of it. P. canaliculata imported to Asia as a cheap food source, they are now causing massive famines destroying large portions of the rice crops and causing some serious food and biodiversity issues.
But since people who struggle to eat are of seeming minimal importance, lets head to Florida with P. insularum where its not so much what they eat but who they displace, they are outcompeting the native apple snails and since they are slightly larger, the kites (large birds) that eat them pick them up, and then can't carry them so drop them on the shores, and the dwindling populations are being deprived of their main if not only food source.
I'm working on them because they are also invading Houston and we expect them to destroy almost all of the vegetation in the Armand Bayou. And to hammer the point in a bit they are thriving because of a harmless invasive plant called elephant ear that allows them to have great places to lay their eggs.
I believe the expected price to tax payers is 22 billion, but because they have twice as many eggs as their cousins and even with predation (which is difficult to find and lacking in the Armand Bayou) have some pretty phenomenal survival rates to adult hood.
I assume this is not the worst invasive but just one that lives near me. Invasive species are like gateway drugs once you have one it sets up for more to come, and the changes to soil composition vegetation balance, those species that "triggers a change in the rules of existence" are the scariest ones we've got, and since this is already way to long I won't go into why putting the same "strongest" species everywhere is a terrible idea.
PS sorry all of my examples only had one famine and one species that was being knocked out, but those are the most preached of each and I was too lazy to actually pull of the research to get more facts.
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