The forecast landscape change incorporating expanses of bioenergy crops planted in monoculture may well create environments conducive to invasive species. Such areas are associated with increased susceptibility to invasion (Hoffman et al. 1995). Weedy and invasive plants will likely be able to take advantage of the disturbed conditions in and adjacent to bioenergy crop fields (Simberloff 2008). Resultant weed management strategies will be critical to establishing and maintaining bioenergy crop production, and to prevent spread of invasive species.

More directly, bioenergy crops, like switchgrass, exhibit a number of characteristics that are correlated with invasiveness. These traits in switchgrass, many of which have been mentioned above, include C4 photosynthesis, a long canopy duration, few known pests and diseases, rapid growth in the early growing season, below-ground partitioning of nutrients in the fall (dormant season), and high water-use efficiency (Raghu et al. 2006). Indeed, many of the traits mentioned here have been championed as the reasons why switchgrass is such a promising biomass feedstock and has attracted U. S. Department of Energy interests (Wright and Turhollow 2010). They are also some of the targets of continued improvement efforts (see Future Prospects below). Bioenergy crops have become invasive in many of the areas they have been planted, even in situations where a particular bioenergy crop species is native to the area (Buddenhagen et al. 2009). Switchgrass itself was recently noted as capable of establishing from seed in disturbed, low-competition areas (Barney et al.

2012) , which could be similar to areas adjacent to agronomic fields.

The prospects of invasiveness of bioenergy crop species are further heightened by the arguments that the only way government benchmarks will be reached is through the use of transgenic crops (Gressel 2008; Sticklen 2009). The inclusion of transgenic energy crops into the landscape matrix in the U. S. carries potential risks related to the transfer of transgenes to related agricultural and wild relatives. This has yet to be thoroughly explored with respect to bioenergy crops, and carries inherent conservation concerns, such as invasive transgenic genotypes via dispersal or introgression, or possibly local extinction of small isolated native populations via genetic swamping of genes that would be selected against (Kwit et al. 2011). There are also regulatory and compliance requirements that would need to be addressed before and after the eventual deregulation and commercial production of transgenic bioenergy crops into the landscape.