Biodiversity and agroenergy: The implications of energy sprawl

Background/Question/Methods

The production of liquid fuels from agricultural biomass (agroenergy) has become a core component of the renewable energy policies of many countries and U.S. states. Agroenergy production places substantial new demands upon lands already responsible for the production of food and the maintenance of biodiversity and the ecosystem services it provides.  Energy sprawl is an increase in the agricultural land area required for the production of dedicated biofuel crops whose impacts to biodiversity remain unclear. As next-generation cellulosic bioenergy crops begin to enter agricultural landscapes, an improved understanding how they impact biodiversity will be critical to designing new and ecologically sustainable agricultural systems.  I undertake a review of the published literature to discuss impacts on biodiversity that result from agrofuel crop selection and management as well as impacts related to the design of landscapes utilized in-part for biofuel feedstock production. 

Results/Conclusions

Compared to conventional agroenergy crops, cellulosic crops (e.g. woody plants and perennial grasses) provide substantial opportunities for enhancing the diversity and abundance of organisms. The benefits of a particular crop to biodiversity appear related to 1) whether the crop is produced in monoculture or more diverse polycultures, 2) the degree to which a crop requires chemical inputs to produce dense biomass and, 3) whether crops are annual vs. perennially-based. Perennially-based polycultures are associated with higher species diversity and abundance, typically experience less disturbance associated with tilling or the application of chemical inputs, and can be harvested in ways that reduce impacts to breeding and migrating vertebrates. Because landcover composition and configurations that optimize certain biodiversity components (e.g. North American grassland birds) are not those that enhance important arthropod groups (e.g. pollinators and biocontrol agents) in biofuel crop fields, crop placement may be more critical to the conservation of rare and economically important species in particular regions. Ultimately, the prospects for capitalizing on the biodiversity benefits of such options will require the intervention of governments to encourage best-production practices and address the direct and indirect drivers of energy sprawl.