Arthropod-mediated ecosystem services in bioenergy landscapes

Background/Question/Methods

Ecosystem services in the form of natural pest suppression by predatory arthropods and pollination by bees are critical to agroecosystems.  Since bioenergy crops will affect both landscape-level and within-farm changes, how and where we use bioenergy cropping systems can have important consequences for a landscape’s ability to provide arthropod-based ecosystem services.

Results/Conclusions

Research across the upper Midwest by the Great Lakes Bioenergy Research Center biodiversity team has found that biomass crops based on floristically diverse, perennial grasslands support diverse and abundant predator communities that contribute to natural pest suppression.  These grasslands also supported more native bee species and enhanced bumble bee colony growth.  At a larger scale, landscape characteristics, in particular the presence of semi-natural perennial grasslands, were associated with an increase in pest suppression potential.  If changes in agricultural land-use affect the potential for biocontrol then we expect that farmers would experience increased pest pressure in areas of the landscape where perennial habitats are relatively less common.  An analysis of county-level data across the upper Midwest showed an increase in pesticides applied to cropland where annual crops were more common (and perennial grasslands were less common), all other things being equal.  Across the region, the absence of perennial habitats was associated with insecticide application to an additional 1.4 million ha, at a cost of $34 - $104 million.

Land-use scenarios in which perennial bioenergy crops are increased on marginal lands show an increase in the capacity of the landscape to support pest suppression and larger and more diverse pollinator communities.  In contrast, increasing acreage of annual crops on marginal lands is expected to decrease biocontrol potential and decrease pollinator abundance and diversity. Thus bioenergy cropping systems based on perennial diverse grasslands have the potential to increase native species with economic consequences.  We hypothesize that developing bioenergy cropping systems that favor an increase in diverse polycultures of perennial plants can produce biomass for energy, promote biodiversity, and enhance landscape-level ecosystem services.