[APWG] Invaders

Mon Sep 15 20:29:19 CDT 2008

I'll have to respectfully disagree that the rate of invasion can't be slowed. For instance, if we had implemented the ballast-water rules we now have several decades ago, we wouldn't be spending many millions of dollars keeping zebra mussels out of water intakes. We can and have slowed the rate of invasion by implementing good practices. Many of our transport and land use practices can be amended to include invasive control. We've implemented best management practices to mitigate the water pollution from construction; why not invasive management as well? We could think of it as "disturbance control". It's easy to regard these policies as burdens and expenses, but that burden and cost is minuscule compared to the (easily measured) economic cost of a single aggressive invader. It's much cheaper to stop 'em than to kill 'em.

I'm not aware that anyone is advocating "war" on all invasives. There are so many that the notion is ridiculous on the face of it. For instance, I don't spend time on removing the mullein on my property; it's just not that aggressive or competitive. On the other hand, a campaign of education is well worth it. This includes practices such as native species plantings by highway departments - example speaks much louder than words. There are many undesirable species which are introduced because they are pretty, and the thought that they could do harm is far removed, even for people who have native plants on their mind. Education practices are essential. I also like the concept of triage. Pick an invasive species or a group of cohabiting species and find the best way to get them under control, then move on to the next most dangerous invader. Eradication is desirable, but is likely impossible under the circumstances. Once the most aggressive invaders are controlled, the native communities may find it easier to reassert themselves. 

Notice I say "communities" rather than "species". I agree with Daniel and Philip that species richness is only one dimension of the health of a biological community; the percentage of sensitive species is a better indicator, and there are many other measures of community health.

I also agree that we should be careful about application of pesticides. In skilled hands the damage from them will be minimal, but there's an awful lot of them being applied. The US Geological Survey has released findings about the ubiquity of glyphosate and its breakdown product in surface water : http://toxics.usgs.gov/highlights/glyphosate02.html . The distribution of herbicides in surface and ground water appears to be most closely related to agriculture, though, especially with the emergence of glyphosate-immune genetically engineered crops. I have to wonder, then, if even generous use of herbicides on invasives can compare to their use in agriculture.

Just some more thoughts.

Mike

-----Original Message-----
>From: Holly Sletteland <hslettel at calpoly.edu>
>Sent: Sep 15, 2008 12:34 PM
>To: Marc Imlay <ialm at erols.com>
>Cc: 'Michael Schenk' <schenkmj at earthlink.net>, apwg at lists.plantconservation.org
>Subject: Re: [APWG] Invaders
>
>I'm coming very late to thisthread, but agree with many of the points made...including Bob'soriginal premise that "I would prefer a morethoughtful approach targeting protection of specific and highlysensitive ecosystems instead of ill advised eradication programs thatare doomed to failure before they begin". I think a lot of money hasbeen wasted going after invasive weeds, primarily because there wasn'ta long term commitment. When that commitment is firmly in place,incredible transformations can occur and monitoring can indeed becomean inexpensive proposition. I have several areas I monitor that wereheavily infested with everything ranging from star thistle to hemlockto Himalayan blackberry, and its really a minor undertaking now. I mayfind one or two plants, sometimes none. Nature is fortunately resilientwent given a hand, and while ecosystems dominated by natives are notimmune to intrusions, they certainly do a better job than highlydisturbed sites. And as a fellow Californian, I am moved and long for areturn to the days when "California hills and valleys were amazingtapestries of color, covered by sweet-scented native wildflowers andbuzzing with native bees" as Daniel so eloquently described. The plantsmay not be extinct, but those landscapes are. I think part of theproblem is that funding for weed eradication programs is often erratic,with a lot of money up front and very little for long term monitoring.I've seen a lot of groups say they would keep it going, only to let itfall by the wayside with the first signs of financial belt tightening.
>
>Marc Imlay wrote:
>
>A Report on the Progressof Invasive Plant Control Program 
>
> 
>
>Maryland NativePlant Society, Anacostia Watershed Society and 
>
>Sierra Club HabitatStewardship Committee Report 
>
> 
>
>Non-native invasivespecies of plants such as English Ivy,Japanese Stiltgrass and Kudzu are covering the natural areas that we intheconservation movement have worked so hard to protect from habitatdestruction,erosion and water pollution.  Just as we are making progress onwetlands,stream bank stabilization, and endangered species, these plants fromotherparts of the world have typically covered 20-90% of the surface area ofourforests, streams and meadows. Many of us feel demoralized and powerlesstocombat these invaders that have few natural herbivores or othercontrols. 
>
> 
>
>The Maryland Native PlantSociety, Anacostia WatershedSociety and Sierra Club are establishing a program to provide localgroups andpublic and private landowners with several models to draw upon in theregion.We are assisting in developing a major 5 year work effort at each sitetoremove massive populations of about a dozen species. Regularstewardshipprojects are conducted in all seasons including winter, early spring,latespring, summer, and late summer.  This high-intensity program isfollowedby a low-intensity annual maintenance program to eliminate plants wehavemissed, plants emerging from the seed bank, and occasional plantsmigrating infrom neighboring areas. We announce regular monthly projects at over 40sitesin Maryland almost all of which wereinitiallystarted as a result of on-the-ground workshops conducted by currentMNPSmembers in CharlesCounty and MontgomeryCounty.The NatureConservancy has also conducted projects on natural areas for manyyears. MNPSand the Sierra Club sponsor the monthly projects at ChapmanForest (800 acres), SwannPark(200 acres) and GreenbeltNational Park(1.5 squaremiles). They co-sponsor Little Paint Branch Park (150 acres) and Cherry HillRoadCommunityPark(15 acres) removals in Beltsville and MagruderParkin Hyattsville MD (15 acres) with the Anacostia Watershed Society andprovideconsiderable assistance to the other projects. 
>
> 
>
>These sites serve as avisible example of what can beaccomplished. 
>
> 
>
>The biggest challenge isto ensure that in subsequent yearsall the successful projects are carried on by responsible entities. Ouradviceto others considering similar projects are to recognize thatrestoration of ournative ecosystem is realistic but requires an appropriate level of workeffort.  
>
> 
>
>Many of us have doneextensive surveys of this area and findthat at least 80% of the natural areas are salvageable with acombination ofmechanical and carefully targeted chemical control and no requirementforre-vegetation. The natives return on their own since they initiallycovered themajority of the surface area. We remove all the class 1 and class 2exoticspecies, typically 5-20 species, because otherwise if you justeradicate oneexotic another one may replace the one removed. 
>
> 
>
>Our policy is to usecarefully targeted, biodegradableherbicides in natural areas, such as glyphosate and triclopyr, that donotmigrate through the soil to other plants. Instead of spraying invasivetreessuch as Ailanthus,  NorwayMaple, and Chinese Privet weinject concentrated herbicide into the tree either by basal bark, hackandsquirt or cut stump. Seedlings are easy to hand pull. We wait for wetsoilafter a rain to hand pull, first loosening with a garden tool such as a4 prongspading fork so the center of the plant rises perceptively. At the 200acre SwannPark,where we are essentially in maintenance phase after 5 years, 17 of the19non-native species are eradicated or nearly so. Only JapaneseStiltgrass andGarlic Mustard remain serious. 
>
> 
>
>All the methods,techniques and/or findings of theseprojects can be used where the initial cover of non-native invasivespecies isless than 30% of the total plant cover and adequately where under 70%cover. Athigher percent coverage the chemical component is more overwhelming andnativeplant re-vegetation may be necessary with native species that are notcultivarsand are obtained from the wild or from nursery stocks originallycollectedlocally in the wild. There are several well researched species mixesthatinclude 12-16 herbaceous and shrub species including nitrogen fixers. 
>
> 
>
>Marc Imlay , PhDConservation biologist, Anacostia Watershed Society 
>
>301-699-6204, 301-283-0808
>
>Board member of theMid-Atlantic Exotic Pest Plant Council, 
>
>Hui o Laka at Kokee State Park, Hawaii
>
>Vice president of theMaryland Native Plant Society, 
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>Chair of the Biodiversityand Habitat Stewardship Committee 
>
>for the MarylandChapter of the Sierra Club. 
>
>Remember our five yeargoal: It is considered standard thatsuch invasive plant removal projects are normally done throughout theregion,the nation, and the world. 
>
> 
>
> 
>
> 
>
>-----Original Message-----
>From: apwg-bounces at lists.plantconservation.org[mailto:apwg-bounces at lists.plantconservation.org] On Behalf Of BobBeyfuss
>Sent: Friday, September 12, 2008 10:15 AM
>To: Michael Schenk; apwg at lists.plantconservation.org
>Subject: Re: [APWG] Invaders
>
> 
>
>Hi All
>
>There is no question thatglobalization has dramaticallyaccelerated the 
>
>spread of invasivespecies but I really do not see anypossibility at all 
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>of that situationchanging in the future. In fact, it islikely to become 
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>much worse in the nextfew decades. The question thatarises, is how do we 
>
>react?  I don't thinkthat simply declaring"war" on all invasive species 
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>anywhere they occur andat whatever rate of infestation isthe answer. The 
>
>older I get, the lessconvinced I am that war is the answerfor most of our 
>
>problems.  I would prefera more thoughtful approachtargeting protection 
>
>of specific and highlysensitive ecosystems instead of illadvised 
>
>eradication programs thatare doomed to failure before theybegin. The 
>
>Director of our localNature Conservancy told me that hecould spend 90% of 
>
>his entire budget for thenext three years, attempting toeradicate 
>
>roadside garlic mustardwith the only certain outcome thathe would have to 
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>start all over again in 3years. When I see eradicationprograms conducted 
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>in highly disturbed urbanenvironments I wonder if the costjustifies the 
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>temporary results.Ultimately, the disturbances that led tothe invasions 
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>remain and often theresults of widespread herbicide applicationsonly 
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>insure that the problem.Unless the entity that is applyingany herbicide 
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>against invasives canreasonably predict that the outcome ofthat 
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>application will resultin the desired reestablishment ofthe plant 
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>community it is designedto protect, I question the action.In simple 
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>terms, killing invasiveplants simply because "they arethere" with no real 
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>clue as to what willfollow, is bad policy.
>
>Bob
>
> 
>
> 
>
>At 11:49 AM 9/11/2008,Michael Schenk wrote:
>
>>Bob, thanks for thearticle.
>
>> 
>
>>This article containsan excellent summary of theunprecedented threat of 
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>>the modern spread ofinvasive species: the vastlyaccelerated rate of 
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>>invasion, coupledwith the stress placed on ecosystemsby induced rapid 
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>>changes. Read throughto the latter part, past thefeel-good stuff about 
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>>the fossil record. Ofcourse the fossil record doesn'tcontain anything 
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>>comparable. There wasno highly mobile technologicalspecies imposing 
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>>geological rates ofchange in decades as opposed tomillions of years.
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>> 
>
>>Change in speciesdiversity and ranges happensconstantly. It's the rate 
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>>of change which isworrisome. The rate of change from amajor asteroid 
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>>strike, scaled inweeks or years, is more similar to thecurrent rate of 
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>>change than themegayears we'll find in the fossilrecord.
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>> 
>
>>Mike
>
>> 
>
>> 
>
>> >Message: 1
>
>> >Date: Wed, 10Sep 2008 14:53:13 -0400
>
>> >From: BobBeyfuss <rlb14 at cornell.edu>
>
>> >Subject: [APWG]Fwd: Friendly Invaders
>
>> >To: apwg at lists.plantconservation.org
>
>> >Message-ID:
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>> >      <6.2.1.2.2.20080910145256.051d6008 at postoffice8.mail.cornell.edu>
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>> >Content-Type:text/plain;charset="iso-8859-1"
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>> >
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>> >
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>> >>X-Mailer:QUALCOMM Windows Eudora Version6.2.5.6
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>> >>Date: Tue,09 Sep 2008 14:11:52 -0400
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>> >>X-PH:V4.1 at granite2
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>> >>To:rlb14 at cornell.edu,<jrh45 at cornell.edu>
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>> >>From: GaryGoff <grg3 at cornell.edu>
>
>> >>Subject:Fwd: Friendly Invaders
>
>>>>X-PMX-Version: 5.3.1.294258, Antispam-Engine:2.5.1.298604, Antispam-Data:
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>> >>2008.7.13.8
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>> >>
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>> >>
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>>>>>X-Mailer: QUALCOMM Windows Eudora Version6.2.5.6
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>> >>>Date:Tue, 09 Sep 2008 08:57:20 -0400
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>> >>>X-PH:V4.1 at granite2
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>> >>>X-PH:V4.1 at tulip
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>> >>>To:CCE-INVASIVESPECIES-L at cornell.edu
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>> >>>From:"Robert J. Kent"<rjk13 at cornell.edu>
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>> >>>Subject:Friendly Invaders
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>> >>>Cc:Charlie Scheer<cfscheer at optonline.net>
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>>>>>X-PMX-Version: 5.3.1.294258,Antispam-Engine: 2.5.1.298604,
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>>>>>Antispam-Data: 2008.8.17.85208
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>>>>>X-PMX-Version: 5.4.1.325704,Antispam-Engine: 2.6.0.325393,
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>>>>>Antispam-Data: 2008.9.9.124319
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>>>>>List-Unsubscribe: <mailto:leave-3026195-7370812N at list.cornell.edu>
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>>>>>List-Subscribe: <mailto:subscribe-cce-invasivespecies-l at list.cornell.edu>
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>>>>>List-Owner: <mailto:owner-cce-invasivespecies-l at list.cornell.edu>
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>>>>>Reply-To: "Robert J. Kent"<rjk13 at cornell.edu>
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>> >>>Sender:bounce-3026195-7370812 at list.cornell.edu
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>>>>>X-LYRIS-Message-Id:
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>>>>><LYRIS-7370812-3026195-2008.09.09-08.57.30--grg3#cornell.edu at list.corne
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>> ll.edu>
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>> >>>
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>> >>>NY Times
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>>>>>September 9, 2008
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>> >>>
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>> >>>
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>> >>>
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>> >>>
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>> >>>FriendlyInvaders
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>> >>>
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>> >>>
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>> >>>
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>> >>>
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>> >>>
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>> >>>By 
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>><http://query.nytimes.com/search/query?ppds=bylL&v1=CARL>>>ZIMMER&fdq=199 
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>>60101&td=sysdate&sort=newest&ac=CARL
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>>>>>ZIMMER&inline=nyt-per>CARL ZIMMER
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>> >>>
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>> >>>New Zealandis home to 2,065 nativeplants found nowhere else on Earth.
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>> >>>Theyrange from magnificent towering kauritrees to tiny flowers that
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>> >>>formtightly packed mounds called vegetablesheep.
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>> >>>
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>> >>>WhenEuropeans began arriving in New Zealand,they brought with them
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>> >>>alienplants ? crops, garden plants andstowaway weeds. Today, 22,000
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>>>>>non-native plants grow in New Zealand.Most of them can survive only with
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>> >>>theloving care of gardeners and farmers.But 2,069 have become
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>>>>>naturalized: they have spread out acrossthe islands on their own. There
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>> >>>are morenaturalized invasive plant speciesin New Zealandthan native 
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>> species.
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>> >>>
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>> >>>Itsounds like the makings of an ecologicaldisaster: an epidemic of
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>> >>>invasivespecies that wipes out thedelicate native species in its path.
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>> >>>But in apaper published in August in The
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>>>>><http://topics.nytimes.com/top/reference/timestopics/organizations/p/pr
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>>oceedings_of_the_national_academy_of_sciences/index.html?inline=nyt-org>Proceedings  
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>> 
>
>> >>>of theNational Academy of Sciences, DovSax, an ecologist at
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>>>>><http://topics.nytimes.com/top/reference/timestopics/organizations/b/br
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>>own_university/index.html?inline=nyt-org>Brown
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>>>>>University, and Steven D. Gaines, a marinebiologist at the University of
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>> >>>California,  Santa Barbara,point out that the invasion has not led to a
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>> >>>massextinction of native plants. Thenumber of documented extinctions of
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>> >>>native New Zealandplant species is a grandtotal of three.
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>> >>>
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>> >>>Exoticspecies receive lots of attentionand create lots of worry. Some
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>>>>>scientists consider biological invasionsamong the top two or three
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>> >>>forcesdriving species into extinction. ButDr. Sax, Dr. Gaines and
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>> >>>severalother researchers argue thatattitudes about exotic species are
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>> >>>toosimplistic. While some invasions areindeed devastating, they often
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>> >>>do notset off extinctions. They can evenspur the evolution of new 
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>> diversity.
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>> >>>
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>> >>>?I hatethe ?exotics are evil? bit, becauseit?s so unscientific,? Dr.
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>> >>>Sax said.
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>> >>>
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>> >>>Dr. Saxand his colleagues are at odds withmany other experts on
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>> >>>invasivespecies. Their critics argue thatthe speed with which species
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>> >>>arebeing moved around the planet, combinedwith other kinds of stress on
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>> >>>theenvironment, is having a major impact.
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>> >>>
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>> >>>There islittle doubt that some invasivespecies have driven native
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>> >>>speciesextinct. But Dr. Sax argues thatthey are far more likely to be
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>>>>>predators than competitors.
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>> >>>
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>> >>>In theirnew paper, Dr. Sax and Dr. Gainesanalyze all of the documented
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>>>>>extinctions of vertebrates that have beenlinked to invasive species.
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>>>>>Four-fifths of those extinctions werebecause of introduced predators
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>> >>>likefoxes, cats and rats. The Nile perchwas introduced into Lake
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>> >>>Victoriain 1954 for food. It then began wiping out native fish by 
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>> eating them.
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>> >>>
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>> >>>?If youcan eat something, you can eat iteverywhere it lives,? Dr. Sax
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>> >>>said.
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>> >>>
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>> >>>But Dr.Sax and Dr. Gaines argue thatcompetition from exotic species
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>> >>>showslittle sign of causing extinctions.This finding is at odds with
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>>>>>traditional concepts of ecology, Dr. Saxsaid. Ecosystems have often been
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>> >>>seen ashaving a certain number of nichesthat species can occupy. Once
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>> >>>anecosystem?s niches are full, new speciescan take them over only if
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>> >>>oldspecies become extinct.
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>> >>>
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>> >>>But asreal ecosystems take on exoticspecies, they do not show any sign
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>> >>>of beingsaturated, Dr. Sax said. In theirpaper, Dr. Sax and Dr. Gaines
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>> >>>analyzethe rise of exotic species on sixislands and island chains.
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>> >>>Invasiveplants have become naturalized ata steady pace over the last
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>> >>>twocenturies, with no sign of slowingdown. In fact, the total diversity
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>> >>>of theseislands has doubled.
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>> >>>
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>> >>>Fishalso show this pattern, said JamesBrown of the
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>>>>><http://topics.nytimes.com/top/reference/timestopics/organizations/u/un
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>>iversity_of_new_mexico/index.html?inline=nyt-org>University
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>> >>>of New Mexico. Hesaid that whenever he visits a river whereexotic fish
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>> >>>havebeen introduced, ?I ask, ?Have youseen any extinctions of the
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>>>>>natives?? ? ?The first response you get is,?Not yet,? as if the
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>>>>>extinction of the natives is an inevitableconsequence. There?s this
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>> >>>articleof faith that the net effect isnegative.?
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>> >>>
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>> >>>Dr.Brown does not think that faith iswarranted. In Hawaii,for example,
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>> >>>40 newspecies of freshwater fish havebecome established, and the 5
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>> >>>nativespecies are still present. Dr. Brownand his colleagues
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>>>>>acknowledge that invasive species can pushnative species out of much of
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>> >>>theiroriginal habitat. But they argue thatnative species are not
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>> >>>becomingextinct, because they competebetter than the invasive species
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>> >>>incertain refuges.
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>> >>>
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>> >>>Thesescientists also point out thatexotics can actually spur the
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>>>>>evolution of new diversity. A NorthAmerican plant called saltmarsh
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>>>>>cordgrass was introduced into England in the19th century, where it
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>>>>>interbred with the native small cordgrass.Their hybrid offspring could
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>> >>>notreproduce with either original species,producing a new species
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>> >>>calledcommon cordgrass.
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>> >>>
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>> >>>Longbefore humans moved plants around,many plants hybridized into new
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>> >>>speciesby this process. ?Something like athird of the plant species you
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>> >>>seearound you formed that way,? Dr. Saxsaid.
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>> >>>
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>>>>>Biological invasions also set off bursts ofnatural selection. House
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>>>>>sparrows, for example, have moved to NorthAmerica from Europe and have
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>> >>>spreadacross the whole continent. ?Naturalselection will start to
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>> >>>changethem,? Dr. Sax said. ?If you givethat process enough time, they
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>> >>>willbecome new species.?
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>> >>>
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>> >>>?Thenatives themselves are also likely toadapt,? Dr. Sax added. Some of
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>> >>>thefastest rates of evolution everdocumented have taken place in native
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>> >>>speciesadapting to exotics. Somepopulations of soapberry bugs in
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>> >>>Florida,for example, have shifted from feeding on a native plant, the
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>> >>>balloonvine, to the goldenrain tree,introduced from Asia by landscapers
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>> >>>in the1950s. In five decades, the smallergoldenrain seeds have driven
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>> >>>theevolution of smaller mouthparts in thebugs, along with a host of
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>> >>>otherchanges.
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>> >>>
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>> >>>In Australia,the introduction of canetoads in the 1930s has also
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>> >>>spurredevolution in native animals. ?Nowthat you have cane toads in
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>> >>>Australia,there?s a strongadvantage for snakes that can eat them,? said
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>> >>>MarkVellend, of the Universityof British Columbia.Cane toads are
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>>>>>protected by powerful toxins in their skin thatcan kill predators that
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>> >>>try toeat them. But in parts of thecountry where the toads now live,
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>> >>>blacksnakes are resistant to the toxins intheir skin. In the parts
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>> >>>wherethe toad has yet to reach, the snakesare still vulnerable.
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>> >>>
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>> >>>Dr.Brown argues that huge negative effectsof invasions are not
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>>>>>documented in the fossil record, either.?You see over and over and over
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>> >>>againthat this is never the case,? hesaid. Species have invaded new
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>> >>>habitatswhen passageways between oceanshave opened up or when
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>>>>>continents have collided.
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>> >>>
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>> >>>?Theoverall pattern almost always is thatthere?s some net increase in
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>>>>>diversity,? Dr. Brown said. ?That seems tobe because these communities
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>> >>>ofspecies don?t completely fill all theniches. The exotics can fit 
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>> in there.?
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>> >>>
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>> >>>In arecent paper in the journal Science,Peter Roopnarine of the
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>> >>>CaliforniaAcademyof Sciences andGeerat Vermeij of theUniversity of
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>> >>>California,  Davis,lookedat the history of invasions among species of
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>>>>>mollusks, a group that includes mussels,clams and whelks. About 3.5
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>> >>>millionyears ago, the mollusks of theNorth Pacific staged a major
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>> >>>invasionof the North Atlantic. Before then,the Arctic Oceanhad created
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>> >>>abarrier, because the mussels could notsurvive in the dark,
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>>>>>nutrient-poor water under the ice.
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>> >>>
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>> >>>A periodof
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>>>>><http://topics.nytimes.com/top/news/science/topics/globalwarming/index.  
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>>html?inline=nyt-classifier>global
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>> >>>warmingmade the Arcticless forbidding. Yet the migration did not lead
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>> >>>to asignificant drop in the diversity ofthe Atlantic native mussels.
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>> >>>Instead,the Atlantic?sdiversity rose. Along with the extra exotic
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>> >>>species,new species may have arisenthrough hybridization.
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>> >>>
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>> >>>The Arctic Oceanis now warming again, this time because of human
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>>>>>activity. Computer projections indicate itwill become ice-free at least
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>> >>>part ofthe year by 2050. Dr. Roopnarine andDr. Vermeij predicted that
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>> >>>today?smollusks would make the sametransoceanic journey they did 3.5
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>> >>>millionyears ago. They also expect theinvasion to increase, rather than
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>>>>>decrease, diversity.
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>> >>>
>
>> >>>Butcritics, including Anthony Ricciardi of
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>>>>><http://topics.nytimes.com/top/reference/timestopics/organizations/m/mc
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>>gill_university/index.html?inline=nyt-org>McGill
>
>>>>>University in Montreal,argue that today?s biologicalinvasions are
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>>>>>fundamentally different from those of thepast.
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>> >>>
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>> >>>?What?shappening now is a major form ofglobal change,? Dr. Ricciardi
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>> >>>said.?Invasions and extinctions havealways been around, but under human
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>>>>>influence species are being transportedfaster than ever before and to
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>> >>>remoteareas they could never reach. Youcouldn?t get 35 European mammals
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>> >>>in New Zealandby natural mechanisms.They couldn?t jump from one end of
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>> >>>theworld to another by themselves.?
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>> >>>
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>> >>>It isestimated that humans move 7,000species a day. In the process,
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>> >>>speciesare being thrown together incombinations that have never been
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>> >>>seenbefore. ?We?re seeing the assembly ofnew food webs,? said Phil
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>> >>>Casseyof the Universityof Birmingham in England.Thosenew combinations
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>> >>>mayallow biological invasions to drivespecies extinct in unexpected 
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>> ways.
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>> >>>
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>>>>><http://health.nytimes.com/health/guides/disease/botulism/overview.html
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>>?inline=nyt-classifier>Botulism,
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>> >>>forexample, is killing tens of thousandsof birds around the Great
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>> >>>Lakes.Studies indicate that two invasivespecies triggered the outbreak.
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>> >>>Thequagga mussel, introduced from Ukraine,filters the water for food,
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>> >>>makingit clearer. The sunlight thatpenetrates the lakes allows algae to
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>> >>>bloom,and dead algae trigger an explosionof oxygen-consuming bacteria.
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>> >>>As theoxygen level drops, thebotulism-causing bacteria can multiply.
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>> >>>Thequagga mussels take up the bacteria,and they in turn are eaten by
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>> >>>anotherinvasive species: a fish known asthe round goby. When birds eat
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>> >>>roundgobies, they become infected and die.
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>> >>>
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>> >>>?If youpour on more species, you don?tjust increase the probability
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>> >>>that oneis going to arrive that?s going tohave a high impact,? Dr.
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>>>>>Ricciardi said. ?You also get thepossibility of some species that
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>> >>>triggersa change in the rules ofexistence.?
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>> >>>
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>> >>>Dr.Ricciardi argues that biologicalinvasions are different today for
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>> >>>anotherreason: they are occurring ashumans are putting other kinds of
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>> >>>stresson ecosystems. ?Invasions willinteract with climate change and
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>> >>>habitatloss,? he said. ?. We?re going tosee some unanticipated 
>
>> synergies.?
>
>> >>>
>
>> >>>Bothsides agree, however, that decisionsabout invasive species should
>
>> >>>be basedon more than just a tally ofpositive and negative effects on
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>>>>>diversity. Invasive weeds can make itharder to raise crops and graze
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>>>>>livestock, for example. The Asianlong-horned beetle is infesting forests
>
>> >>>acrossthe United Statesand is expected toharm millions of acres of
>
>> >>>hardwoodtrees. Zebra mussels have cloggedwater supply systems in the
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>>>>>Midwestern United States. Exoticspecies canalso harm humans? health.
>
>>>>>?<http://health.nytimes.com/health/guides/disease/west-nile-virus/overv
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>>iew.html?inline=nyt-classifier>
>
>> >>>West Nilevirus,
>
>>>>><http://health.nytimes.com/health/guides/disease/the-flu/overview.html?  
>
>>inline=nyt-classifier>influenza
>
>> >>>? thesethings are invasions,? Dr.Ricciardi said.
>
>> >>>
>
>> >>>On theother hand, some invasive speciesare quite important. In the
>
>> >>>UnitedStates, many crops are pollinated byhoneybees originally
>
>>>>>introduced from Europe.
>
>> >>>
>
>> >>>?It?snot that this is all good or all bad,and I?m not sure science
>
>> >>>shouldbe the arbiter,? Dr. Brown said.?Placing values on these things
>
>> >>>is thejob of society as a whole.?
>
>> >>
>
>>>>-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:  
>
>>-:-:-:-:-:-:-:-:-:-:-:-
>
>> >>
>
>> >>Gary R. Goff
>
>> >>104 FernowHall, CornellUniversity, Ithaca, NY14853.
>
>> >>ph.607/255-2824;  fax 607/255-2815; e-mail: grg3 at cornell.edu
>
>>>>www.cornellmfo.info
>
>>>>http://www.dnr.cornell.edu/people/ra/profiles/goff.html
>
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>
>> >
>
>>>------------------------------
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>> >
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>>>_______________________________________________
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>>>APWG at lists.plantconservation.org
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>>>http://lists.plantconservation.org/mailman/listinfo/apwg_lists.plantconse
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>> rvation.org
>
>> >
>
>> >
>
>> >End of APWGDigest, Vol 60, Issue 3
>
>>>***********************************
>
>> 
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>> 
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>> 
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>> 
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>> 
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>Disclaimer                                                                 
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>_______________________________________________PCA's Alien Plant Working Group mailing listAPWG at lists.plantconservation.orghttp://lists.plantconservation.org/mailman/listinfo/apwg_lists.plantconservation.orgDisclaimer                                                                Any requests, advice or opinions posted to this list reflect ONLY the opinion of the individual posting the message.
>-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Holly SlettelandPreserve ManagerMorro Coast Audubon SocietyP.O. Box 1507Morro Bay, CA 93443Phone: (805) 239-3928