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Practice Reading: Reading Fill in the Blanks ID: #50577 Non-indigenous Plants
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The  invasion  of  non-indigenous  plants  is  considered  a  primary  threat  to  integrity  and  function  of  ecosystems.  However,  there  is  little  quantitative  or    evidence  for  ecosystem  impacts  of  invasive  species.  Justifications  for  control  are  often  based  on  potential,  but  not  presently  realized,  recognized  or  quantified,  negative  impacts.  Should  lack  of  scientific  certainty  about  impacts  of  non-indigenous  species  result  in  postponing  measures  to  prevent  degradation?  Recently,  management  of  purple  loosestrife  (Lythrum  salicaria),  has  been  criticized  for  lack  of  evidence  demonstrating  negative  impacts  of  L.  Salicaria,  and  management  using  biocontrol  for  lack  of  evidence  documenting  the  failure  of  conventional  control  methods.  Although  little  quantitative  evidence  on  negative  impacts  on  native  wetland  biota  and  wetland  function  was  available  at  the  onset  of  the  control  program  in  1985,  recent  work  has  demonstrated  that  the  invasion  of  purple  loosestrife  into  North  American  freshwater  wetlands  alters    rates  and  nutrient  cycling,  leads  to  reductions  in  wetland  plant  diversity,  reduces  pollination  and  seed  output  of  the  native  Lythrum  alatum,  and  reduces  habitat    for  specialized  wetland  bird  species  such  as  black  terns,  least  bitterns,  pied-billed  grebes,  and  marsh  wrens.  Conventional  methods  (physical,  mechanical  or  chemical),  have  continuously  failed  to    the  spread  of  purple  loosestrife  or  to  provide  satisfactory  control.  Although  a  number  of  generalist  insect  and  bird  species  utilize  purple  loosestrife,  wetland  habitat  specialists  are  excluded  by  the    of  L.  salicaria.  We  conclude  that  negative  ecosystem  impacts  of  purple  loosestrife  in  North  America  justify  control  of  the  species  and  that    effects  of  purple  loosestrife  on  wetland  systems  and  biota  and  the  potential  benefits  of  control  outweigh  potential  risks  associated  with  the  introduction  of  biocontrol  agents.

devastating sustainability experimental suitability decomposition composition curb detrimental encroachment

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