1. CONTACT: Koldo Saez de Bikuña (ksde@kt.dtu.dk) Biotic Stocks Potential: an improved indicator for Land Use impact assessment? Potential Natural Vegetation as Reference Land Koldo Saez de Bikuña 1, Andreas Ibrom 1, Michael Zwicky Hauschild 2 1: Center for Ecosystems and Environmental Sustainability, Department of Chemical and Biochemical Engineering, Technical University of Denmark (Risø), Roskilde, Denmark. 2: Division for Quantitative Sustainability Assessment, Department of Management Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark. Solutions suggestedProblem statement Biotic Stocks Potential vs. Biotic Production Potential 1) Establish an assessment framework that allows quantifying biomass trade-offs in support of optimal decision-making concerning Land Use (LU). 2) Substitute BPP by BSP (Biotic Stocks Potential) as a more complete and meaningful LU impact indicator. 3) Use a Universal Reference Land for LU impact assessment to reduce biases that arise from user choices. 1) Within Life Cycle Assessment (LCA), a holistic ISO methodology for quantitative sustainability assessment, biotic production has been suggested to be the main Ecosystem Service provided by soils to humans [1]. 2) Biotic Production Potential (BPP) has been suggested to be measured by Net Primary Production (NPP) [2]. On the other hand, evidence has shown a Planetary Boundary for NPP in a global scale [3]. 3) There is currently no consensus over the Reference Land for land use change impact assessment, which renders the assessment highly arbitrary. Biotic Stocks Potential (BSP) accounts for all biotic carbon stock (biogenic and soil C- pools) and their changes of a certain land over a period of time.  Advantages of BSP over BPP : I.33% of all anthropogenic C-emissions come from decreased C–stocks in soil & biogenic C-pools (historical LU changes) [4]. BSP is capable of showing the full historical carbon debt of that LU, while variations in regional BPP are generally small (Fig. 1). II.Despite continuous LU change world-wide, global NPP seems to remain constant over time [3]. This renders current BPP a weak and possibly misleading indicator, while BSP shows a more meaningful and complete picture (Fig.1). III.BSP enables a proper accounting of Climate Change (CC) impacts of bioenergy [5]. CC mitigation potential loss due to max FF displacement BSP (Mg C ha -1 yr -1 ) BPP* (Mg C ha -1 yr -1 ) References : [1] Milà I Canals et al.: Key Elements in a Framework for Land Use Impact Assessment Within LCA, Int. Journal of LCA, 12 (2007), 5–15. [2] Beck, D.T. et al.: Land Use Indicator Value Calculation in Life Cycle Assessment – Method Report, Fraunhofer Institute (2013) [3] Running, SW: A Measurable Planetary Boundary for the Biosphere, Science (New York, N.Y.), 337 (2012), 1458-9. [4] IPCC Fourth Assessment Report, 2007. [5] Searchinger, T. Fixing a critical climate accounting error. Science (New York, N.Y.), 326 (2009), pp.527–528 Figure 1. BSP vs BPP: a study case. Potential Natural Vegetation (PNV) is the spontaneous, locally adapted plant combination that form a site-inherent ecosystem that develops over successive years on an undisturbed land [1]. I.Hypothesis 1: PNV gives the maximum BSP that can be obtained in that land without anthropogenic inputs, and therefore without additional impacts  PNV can then work as a Universal Reference Land for LU impact assessment. II.Hypothesis 2: PNV can also be a proxy for additional Ecosystem Services benchmarking: Soil quality Biodiversity Climate regulation Erosion regulation Water recharge & purification III.BSP impacts: BSP Absolute: ∆BSP willow SRC = 165,9 Mg C ha -1 year -1 (C-stocks potential deficit) BSP Index:BSP Index, willow SRC = ∆BSP i / BSP Ref. (PNV). = 0,43 BPP NPP BSP NPP 86428642 50100150200250300350 FF displacement potential CC mitigation potential Figure 2. Framework for assessing trade-offs of biomass for energy purposes. When a land is managed to maximize its yields (BPP, case of willow SRC), a loss occurs in its potential to store carbon in its different pools (CC mitigation potential loss, Red area). If this land is managed to maximize its carbon storage capacity (BSP of PNV, case of Beech forest), a loss occurs in its potential to provide for energy to society (FF displacement potential loss, Blue area). Maximizing biomass for Fossil Fuel (FF) displacement or CC mitigation? Beech forest (PNV) Willow SRC FF displacement potential loss due to max BSP Abbreviations: BG C: Belowground C; AG C: Aboveground C Willow SRC: Willow Short Rotation Coppice Conclusions BSP seems a good candidate to substitute BPP for LU impact assessment methods. PNV offers a promising solution to the Reference Land problem, not without challenges. A possible framework for weighting biomass trade-offs has been drawn. BPP* = Harvestable NPP The biomass dilemma