Great Lakes Bioenergy Research Center; Michigan State University, United States
Background/Question/Methods
Bioenergy cropping could transform landscapes in coming decades and have sweeping impacts on biodiversity. The nature of these changes is uncertain and will depend on which crops are adopted, how they are managed, and which types of ecosystems they replace. We censused multiple taxonomic groups in a long-term experimental array in southwest Michigan, US, containing ten replicated bioenergy cropping systems. The cropping systems spanned a gradient including intensive annual crops (corn, two sorghum systems), simple perennial systems (Miscanthus, two switchgrass systems, and a native prairie grass mix), and complex perennial polycultures (reconstructed prairie, successional vegetation, and short-rotation poplar). The taxonomic groups we censused included plants, bees, butterflies, ants, birds, small mammals, soil micro-invertebrates, fungi, bacteria, and protists in each crop type.
Results/Conclusions
Compared to corn, which is the business-as-usual bioenergy crop in our region, richness of most groups was equal or lower in sorghum-based systems and tended to be higher in perennial systems. For many groups, species richness gains in simple perennial systems (dominated by one or a few grass species) were modest and were much higher in complex perennial systems (reconstructed prairie, successional vegetation, and poplar). This pattern was most striking for bees, butterflies, ants, birds, and fungi. Microbial groups tended to be more diverse in perennial systems, but responses were eclectic and depended on whether samples were taken from leaves, roots, or the soil matrix. Our findings illustrate the wildly contrasting biodiversity outcomes that bioenergy adoption could bring about. Responding to energy demands by expanding annual cropping systems or converting natural habitats to simple perennial systems will have strongly adverse effects for biodiversity; in contrast, replacing marginal annual crops with diverse perennial bioenergy systems could greatly enhance biodiversity in simplified agricultural landscapes.
