The EU climate action and renewable energy package has set a target of increasing the share of renewables in energy use to 20 per cent by 2020 which includes a minimum 10 per cent share for renewable energy in transport by 20201. The package sets out sustainability criteria for biofuels to ensure they deliver real environmental benefits. It is therefore important to establish methods to assess the environmental profile of a bioenergy crop before it is introduced to an area or planted extensively.
Invasive species raise concerns for biodiversity at both a European and global level and is a major policy issue2. To date, no study has quantified the invasiveness of bioenergy crops. This study adapted an established tool called the Weed Risk Assessment (WRA) for use in Hawaii and the Pacific regions. The WRA mitigates the impacts of intentional plant introductions. The research compared the risks of invasion of a list of 40 bioenergy crops that have been proposed for Hawaii to a random sample of 40 non-bioenergy plants that have already been introduced. The research is valid for all areas with tropical and subtropical ecosystems.
The results demonstrated that bioenergy crops were 2 to 4 times more likely to be invasive or establish wild populations in Hawaii. Using the adapted WRA's threshold for high risk, the research identified 70 per cent of bioenergy species as high risk compared to a quarter of a random selection of introduced non-bioenergy species. The same WRA system is easily adapted for local use, and has been shown to be effective around the world in various climatic zones including Europe3.
These findings provide real evidence to support concerns voiced by previous studies that bioenergy crops are likely to be invasive, because they are selected for many of the same traits that belong to successful invasive species. Traits include pest resistance, high biomass or reproductive capacity, tolerance to harsh conditions and an ability to thrive as a large monoculture. Extensive planting - expected under large-scale bioenergy crop cultivation - will encourage invasions. There is further cause for concern if the invasions are near vulnerable natural areas with high-value biodiversity.
However, the authors also point out that not all the high risk species are equally problematic and some could be regulated and managed to ensure their benefits outweigh their costs. Key invasive potential bioenergy species include gorse, jatropha and kudzu. Non-invasive examples include macadamia and sugarcane.
The study suggests that governments should consider the invasiveness of bioenergy crops when granting funds or approval. It also suggests they should apply the 'polluter pays' principle in order to mitigate potential negative impacts.