The known unknowns—managing the invasion risk from biofuels

The uptake of second generation biofuels poses a range of risks including that of creating new invasive species. Plant invaders are a major threat to sustainability, economically and environmentally. Assessing the risk that plants will become invasive appears – paradoxically – to be attainable in practice, but difficult in theory. We explore the reasons for this, and inject a note of caution into the prospects for prediction. Instead, we endorse a precautionary approach, involving risk management and the phased scaling up of biofuel crops, accompanied by monitoring for untoward impacts, stringent analysis of prospective benefits, and the utilization of cultivated native species.