(Editor's Note: This article was originally published on March 22, 2011. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)
We paint the invaders with a broad brush, splashing a sign on them that says "detrimental to this ecosystem." Our first impulse is to compare virgin and disturbed areas, and tally the lost native plant populations. Then we calculate the effects on species which use those lost plants. However, researchers at Penn State University have approached the question from another angle. Can native creatures adapt to, and benefit from, recently introduced plants? They say yes. Researchers at Penn State University have found that one nonnative invasive species studied appears to help native fauna and flora.
ScienceDaily® reports here on a project by assistant professor Tomás Carlo and graduate student Jason Gleditsch of Penn State University. Perhaps acknowledging a certain futility in battling invasive species, they asked a new question. Carlo wondered "Are we sometimes doing more harm than good when we eradicate plants that, despite being introduced recently, have formed positive relationships with native animals?"  The Pennsylvania research team studied invasive honeysuckle and native fruit-loving birds. In a rare instance of good news in the invasive species research field, local birds are thriving in the presence of the honeysuckle. The honeysuckle provides a good food source for catbirds, robins, and other wild birds in the area. Compounding the good news is further experimentation with native nightshade in the region. As bird presence and activity increases, so does the dispersal of seed from nightshade. In other words, more birds means a healthier population of the many plants on which they feed. One conclusion from the study is that in those areas where humans have created a niche for a nonnative, that species may bring measurable and diverse benefits to the ecosystem.
Research by a group of scientists in the Mediterranean somewhat echoes these results. In this case, study plants and their pollinators were observed. The news was not quite as rosy as that in Pennsylvania. One study plant, a prickly pear, monopolized its pollinating bee, probably causing harm to other plants. However, another invasive plant attracted more pollinating insects than were otherwise expected. The greater level of insect activity may mean better fertility and seed production for native plants. 
Like the Pennsylvania robins, could our native nectar and pollen feeding insects be reaping benefits from the floriferous purple loosestrife? Maybe they are. In the meantime, research has identified two species of leaf eating beetle with voracious appetites for the Lythrum salicaria. The beetles have been employed in a large scale efffort to control the invasive loosestrife. Any gardener who has warred with cucumber beetles, asparagus beetles, or flea beetles in the home garden must respect the power of hordes of crunching chrysomelids. Similary, these Galerucella beetles from Europe can devastate individual loosestrife plants. After careful study, beetles were released on stands of loosestrife beginning in 1992. One local agency, the Stevens County Noxious Weed Control Board, reports that beetle populations in their jurisiction are self-sustaining, and are sucessfully reducing stands of loosestrife.  This success is also ocurring across the United States.
When control for control's sake fails, creative capitalists dream of "control" through finding commercial uses for invasive plants. After all, nothing can crash a species' population faster than profit potential and ensuing exploitation. Study has been done in using kudzu, giant reed, or certain other grasses as raw material for biofuel production. The superefficient growth of invasives makes them an attractive choice for producing the biomass needed for fuel production.  But biofuel is not the easy answer it once seemed. Perhaps the "use" of invasives should start with a more direct, less industrial, use of the biomass.
For some years now, The Hop Brook Protection Agency has been mechanically clearing tons of aquatic invasive plants from Carding Mill Pond in Sudbury, Massachusetts. The green material threatened to kill fish and choke out wildfowl. Any gardener knows that waste plant material can be a mainstay in composting; so do farmers around Sudbury. They've been accepting the green wet material and using it to build organic content in farm fields. As garlic farmer Michael O'Connor says, the dredged material is "inexpensive, organic, abundant and very beneficial to the soil. "  An interesting aspect to this situation is that the overabundance of water weeds there is partially due to nutrient overlaoding from a wastewater treatment plant. Therefore, in this scenario, the aquatic plants help complete the cycling of nitrogen and phosphorus introduced to the local ecosystem by human presence. 
What lies down the road along our "path" lined with nonnative, invasive plants? At this stage, we don't fully know. Certainly we need to continue the studies and activities that ask not only "Can we, and how should we eradicate invasives" but also "should we even try?"
~ endnotes ~
 Penn State. "Invasive plants can create positive ecological change." ScienceDaily 14 February 2011. http://www.sciencedaily.com /releases/2011/02/110211095555.htm.
 Plataforma SINC. "Native Plants Can Also Benefit From The Invasive Ones." ScienceDaily 21 May 2008. http://www.sciencedaily.com/ /releases/2008/05/080516125934.htm.
 Galerucella pusilla (golden loosestrife beetle)Stevens County Noxious Weed Control Board 23 February 2011.
 Raghu, S. et al, "Adding Biofuels to the Invasive Species Fire?" Science 22 September 2006. http://energyandenvironmentblog.dallasnews.com/invasive%20species%20and%20biofuels.pdf
 Hershfield, Nancy. "Garlic farmer uses compost harvested from invasive plants at Carding Mill Pond," The Sudbury Town Crier 5 November 2009.