Giant cane, a potential biofuel crop, is a noxious invader of streams and wetlands. Image Source: WikipediaThe search for new biofuels has effectively created an entire new category of agriculture, along with which comes a host of new management risks.  The cycles of crop growth and failure may be less well known than those of more familiar food crops, and they may be affected by new pests and disease.

A particularly worrisome area of risk associated with biofuel crops is the possibility that the crops themselves may become noxious pests in countries to which they are imported.  In the current issue of Frontiers in Ecology and the Environment, Adam Davis et al. review what is known about such invasions and how to manage them. 

Biofuel crops are likely to invade ecosystems because many of the traits that make them attractive to grow (fast growth, low resource requirements, adaptable to many environments) are exactly those that help them out-compete native plants.   Woody species introduced as fuel crops in Africa in the Middle east have caused ecological damage.  In the U.S., Giant Cane (Arundo donax) has invaded and choked off streams and wetlands, and is all but impossible to eradicate once established, yet it is actively promoted as a fuel crop in the Gulf States.

The authors point out that systems to identify plants as possible invaders exist.  Australia's Weed Risk Assessment System (WRA), for instance, has had 95% success in predicting species likely to become damaging invaders by evaluating them on whether they exhibit a series of weed-like ecological traits.  However, a 95% success rate still means that 1 in 20 plants introduced can become harmful invaders, and far more than 20 plant species are being evaluated by entrepeneurs and researchers as candidates for new biofuel feedstocks.  Given the amount of ecological data required, achieving a better success rate such as 99% from such systems is unlikely.

How then should we manage the risk of invaders while searching for new crops?  The authors suggest a two-tiered system, where plants passing a checklist-based system like the WRA are then subjected to experimental plantings to determine if they can thrive in the absence of any human cultivation.  More stringent criteria are given for those plants for which little current data exists on invasive traits.  The "nested-seive" approach has a much lower likelihood of letting potential invaders through. Davis, A., Cousens, R., Hill, J., Mack, R., Simberloff, D., & Raghu, S. (2010). Screening bioenergy feedstock crops to mitigate invasion risk Frontiers in Ecology and the Environment, 8 (10), 533-539 DOI: 10.1890/090030

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