Ecology of agricultural monocultures: Some consequences for biodiversity in biomass energy farms

Abstract

Most developmental work on biomass crops has involved extensive monocultures of genetically uniform crops. We review the relevant ecology of agricultural monocultures, and some consequences of monocultural methods for the biomass industry. Monocultures can have very high primary productivity; indeed biomass crops are selected for high productivity. The seasonal tempo of productivity is often more punctuated in monocultures than in multispecies system, leaving temporal productivity gaps. In turn, folivorous insect diversity and abundance tends to track the foliage productivity. The productivity gaps may produce bottlenecks in herbivore abundance and diversity. Herbivore population dynamics tend to be less stable in monocultures, driving fluctuations in predator abundance and diversity. These bottlenecks and fluctuations can increase the frequency and severity of pest problems, for herbivorous insects usually respond to productivity increases faster than their predators. The spatial scaling of structural complexity is also critical to habitat value, particularly for vertebrates. At micro scales structural complexity is a function of plant structure. At meso scales, agricultural monocultures tend to be very uniform, compared to multispecies systems, and provide poorer habitat for species needing meso-scale diversity. We suggest three strategies to enhance or restore biodiversity while developing biomass crops. First, tailor the scale of plantingsmore » to the needs of wildlife in the system. Second, manage the deployment of the biomass plantings to be complementary to other landscape features. For example, concentrate biomass plantings on the most favorable sites in the landscape, and develop complementary habitat inclusions on poorer microsites. Third, develop crops and crop combinations to benefit wildlife as well as to provide high yields. Select and deploy crops and clones to bridge productivity gaps.« less