Making environmental assessments of biomass production systems comparable worldwide

Global demand for agricultural and forestry products fundamentally affects regional land-use change associatedwith environmental impacts (EIs) such as erosion. In contrast to aggregated globalmetrics such as greenhouse gas (GHG) balances, local/regional EIs of different agricultural and forestry production regions needmethodswhich enable worldwide EI comparisons. The key aspect is to control environmental heterogeneity to revealman-made differences of EIs between production regions. Environmental heterogeneity is the variation in biotic and abiotic environmental conditions. In the present study, we used three approaches to control environmental heterogeneity: (i) environmental stratification, (ii) potential natural vegetation (PNV), and (iii) regional environmental thresholds to compare EIs of solid biomass production.We compared production regions ofmanaged forests and plantation forests in subtropical (Satilla watershed, SoutheasternUS), tropical (Rufiji basin, Tanzania), and temperate (Muldewatershed, Central Germany) climates. All approaches supported the comparison of the EIs of different land-use classes between andwithin production regions. They also standardized the different EIs for a comparison between the EI categories. The EIs for different land-use classes within a production region decreasedwith increasing degree of naturalness (forest, plantation forestry, and cropland). PNVwas themost reliable approach, but lacked feasibility and relevance. The PNVapproach explicitly includedmost of the factors that drive environmental heterogeneity in contrast to the stratification and threshold approaches. The stratification approach allows consistent global application due to available data. Regional environmental thresholds only included arbitrarily selected aspects of environmental heterogeneity; they are only available for fewEIs. Especially, the PNV and stratification approaches are options to compare regional EIs of biomass or crop production such as erosion, biodiversity, or water quality impacts worldwide and thereby complement existingmetrics assessing global EIs such asGHGemissions.