Global Conservation Issues

Exotic species and bioenergy: Potential for introducing or spreading invasive plants

Joseph DiTomaso

Friday, October 17, 2008 - 11:00-11:30

In response to growing energy demands and climate change awareness, alternative energy sources are being sought. Biomass-derived energy from dedicated biofuel crops is being researched by many nations with exotic rhizomatous perennial grasses as leading candidates. Biofuel crops are being selected/bred/engineered because they are highly efficient (e.g., water, nutrients), tolerate poor growing conditions (e.g., drought or infertile soils), possess few resident pests, and produce highly competitive monospecific stands. These desired agronomic traits typify much of our invasive flora and pose a potential threat if these crops become invasive pests. To test the potential invasiveness of leading biofuel candidate crops, including switchgrass, giant reed, and miscanthus, we used the Weed Risk Assessment protocol to qualify risk potential. In addition, we are conducting ecological studies of fitness responses to various environmental and disturbance scenarios which will provide data in climate-matching models to predict the potential invasiveness of biofuel species in a variety of ecosystems. Breeding and genetic engineering for enhanced environmental tolerance (e.g., drought tolerance), increased harvestable biomass production (e.g., lower root-to-shoot ratio), and enhanced energy conversion through fermentation (e.g., lower lignin content) may have unexpected ecological consequences outside the agronomic framework. For example, using the WRA protocol, switchgrass was found to have a high invasive potential in California unless sterility was introduced. The potential societal benefits of a biologically-based energy supply are great, but the introduction and development of biofuel crops should be conducted to minimize the risk of these proposed feedstock species escaping cultivation and causing economic or environmental damage.

Keywords: BIOFUELS, INVASIVE SPECIES, WEED RISK ASSESSMENT