Some floated here on boats. Others flew. Still others arrived on the sole of a dirty boot. Many were invited, but some arrived unannounced. At this point, however, no one really cares how so-called alien species like the ash borer and the zebra mussel got here. Scientists are more focused on how to get rid of these pests.

Not every alien species becomes invasive, but those that do can wreak serious havoc. They eat or out-compete native species. They clog waterways and cover coral reefs. They reproduce wildly and turn once-diverse ecosystems into single species monocultures. In one extreme example the introduction of the invasive Nile perch into Lake Victoria in Africa in the 1960s led to the disappearance of as many as 200 native cichlids. In the U.S. a fast-growing Japanese vine called kudzu has blanketed large portions of the Southeast, knocking down trees and smothering native species under its dense canopy.

As international travel has become more common the problem has only gotten worse. People and cargo regularly cross mountain ranges, rivers, oceans and deserts—features that once kept plants, animals and insects apart. In the past century invasive species have infiltrated nearly every part of the globe. There are more than 1,500 invasive species in the U.S. alone, says Daniel Simberloff, an ecologist at the University of Tennessee Knoxville. No one has compiled a global list, but it would likely include 10,000 species or more, he says.

Scientists are trying to stem the influx of new invasive species as well as control the intruders that have already infiltrated native ecosystems. But these opponents are wily. They've gained a foothold and won't easily let go. Luckily, when it comes to combating invasive species ecologists these days are getting creative. You try everything you can to fight them, says Michael Massimi, invasive species coordinator at Barataria–Terrebonne National Estuary Program in Louisiana. "When you reach the end of your rope and nothing is working, you start trying the crazy stuff."

View a slide show of how scientists are dealing with some of these unwelcome interlopers

13 Comments

1. 1. ormondotvos 05:01 PM 6/28/10

   Goats v. Kudzu?

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2. 2. ormondotvos 05:12 PM 6/28/10

   Flying food fish?

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3. 3. ssm1959 06:26 PM 6/28/10

   My family has been fighting this battle for 45 years on a timber farm in southern Wisconsin. There are many hard earned lessons over those years that need to be kept in mind. First, what is the natural history of the species in the new environment. Many species present with an initial invasive flush which fades over a few years leaving the new species in an equilibrium. You cannot win against these not do you have to. The environment will control them. Those species that experience an unrelenting release phenomenon is where you have to throw the limited resources. This group is made up of both native and non-native species. before you declare war on them be sure to assess ALL!!!!!!! contributors to the problem. For example: Eurasian buckthorn did not take off until deer populations exceed 35 per square mile. As the deer mowed down the native species that competed it left buckthorn an uncontested niche. Our efforts in controlling this infestation were wasted until we brought the deer numbers down to a more reasonable level.
   
   In all instances, consider the use of fire and /or mowing prior to herbicide. Fire is far more effective in its cost and application than paying people to runaround spraying chemicals that will only work at the spot applied and only for the phase of growth targeted. Timely mowing will reduce seed production but is must be done after the plant has set and has no chance of flowering again. Fire, my personal fav, works wonders. It targets all phases of growth and may have inhibitory effects in the soil as well.
   
   In all cases read, scrutinize and analyze before committing. You can help stem the tide locally which is the best you can do in most cases.

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4. 4. hankroberts 11:08 PM 6/30/10

   http://scholarsarchive.library.oregonstate.edu/jspui/handle/1957/2885
   
   Sucrose and sawdust application on cheatgrass removal
   
   I tried spraying sugar water after a recent fire on a restoration site I've been poking at for a few decades -- the idea is to feed the soil microbes so they take up all the excess minerals left near the surface by the fire, and then the next spring the cheatgrass starves while the deep-rooted native plants get a chance to recover.
   
   The result for this amateur trial looked quite good. Other studies on this idea have been coming out recently.

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5. 5. sparcboy 10:25 AM 7/1/10

   Surprising no mention of an invasive species that affects much of the southern U.S.: Feral Hogs.

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6. 6. rhinoguy 02:52 PM 7/1/10

   I don't see how hunting nutria for their fur would be an effective way of managing/controling/removing an exotic species. What, when the nutria hear how cruel we are to the ones we've caught the rest will get scared and leave? Aren't there alternatives to this? If there is no more humane or sensible way of removing the nutria from Louisiana than convencing hunters that they would make great jackets, aren't we still working with or at the level of the mentality that has caused so much trouble with wildlife management to begin with? Wouldn't live trapping, sterilization, and returning the animal to the exotic habitat to mate unsuccessfully be a more realistic and humane way of doing this? It goes back to the old idea that it's probably not the best idea to put animal management in the hands of people who get such a kick out of slaughtering them.

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7. 7. jar2353 01:35 PM 7/2/10

   We have certainly handled the "Invasive Species" infecting our border states.
   Why not apply the same method: Do Nothing!
   (except when we need votes)

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8. 8. J. Howard 06:13 PM 7/2/10

   In Rochester, New York, a coalition formed by the Sierra Club and other community organizations and individuals has begun a project to control invasives, primarily Norway maple, in a unique hardwood grove in the City. We welcome ideas and contact with other groups trying to do similar projects in a city. We have found that many people in the community resist removal of the Norway maples and have a limited understanding of the potential for change in native ecosystems that can be effected by invasive plants.

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9. 9. prachitripathi 11:48 PM 7/2/10

   this so called artist is promoting fur, no matter how much she denies it. once it catches public fancy there will be huge demand and not only nutrias but other furry native species will also suffer. nutrias did not swim across the oceans from south america to invade the wetlands of united states. a more humane way to control them should be thought of and the fur lobby who bring in these exotics and are responsible for their escape into the wild should pay. and by the way, is there no risk analysis worked out before a new species crosses borders? i think thats where we need to put a check.......its stupid to slaughter them for no fault of theirs.

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10. 10. prachitripathi 11:49 PM 7/2/10

    Even the animal's enormous orange teeth have made it onto the runway as necklaces and earrings. "When they're attached to a nutria they're pretty hideous," Massimi says. "But when you mount them on some Balinese silver, they actually look quite nice.".......................THE LAST LINE BEATS IT ALL. SO INHUMAN.

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11. 11. bucketofsquid 09:56 AM 7/6/10

    jar2353 - you are a racist pig and no one likes you. Take your hate mongering over to Fox News where it belongs.
    
    Rhinoguy and Prachitripathi - Predators kill and eat things all of the time. It is the natural way. These nutria are a threat to the survival of huge numbers of species so yes they are at fault just by existing. The people that brought them in have been dead for decades. How are dead people going to pay for anything? How many nutria can be captured and sterilized each year? 400,000? A million? Any less than this is meaningless.
    
    Personally, I think nutria hunting should be encouraged as a good recreational "green" sport. Boy Scouts could have community service nutria kills. It is a winning solution.
    
    

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12. 12. bucketofsquid 09:58 AM 7/6/10

    The forum software used by SciAm is terrible.

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13. 13. macadamia man 10:37 PM 7/8/10

    @prachitripathi
    
    "THE LAST LINE BEATS IT ALL. SO INHUMAN."
    
    I'd say your line should read so inhumane. All too human . .

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