Concerns about global climate change and air quality have increased interest in biomass and other energy sources that are potentially COz-neutral and less polluting. Large-scale bioenergy development could indeed bring significant ecological benefits - or equally significant damage - depending on the specific paths taken. In particular, the land requirements for biomass production are potentially immense. Various entities in the United States have performed research; prepared cost-supply assessments, environmental impact assessments, life cycle analyses and externality impact assessments; and engaged in demonstration and development regarding biomass crops and other potential biomass energy feedstocks. These efforts have focused on various biomass wastes, forest management issues, and biomass crops, including both perennial herbaceous crops and fast-growing woody crops. Simultaneously, several regional and national groups of bioenergy stakeholders have issued consensus recommendations and guidelines for sustainable bioenergy development. It is a consistent conclusion from these efforts that displacing annual agricultural crops with native perennial biomass crops could - in addition to reducing fossil fuel use and ameliorating associated ecological problems also help restore natural ecosystem functions in worked landscapes, and thereby preserve natural biodiversity. Conversely, if forests are managed and harvested more intensively - and/or if biomass crops displace more natural land cover such as forests and wetlands - it is likely that ecosystem functions would be impaired and biodiversity lost. (C) 2000 Elsevier Science Ltd. All rights reserved.