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Abstract:
Six of nine planetary boundaries are currently transgressed, many related to human land use. Conversion of sizeable land areas to biomass plantations for Bioenergy with Carbon Capture and Storage (BECCS) – often assumed in climate mitigation scenarios to meet the Paris Agreement – may exert additional pressure on terrestrial planetary boundaries. Using spatially-explicit, process-based global biogeochemical modelling, we systematically compute feedstock production potentials for BECCS under individual and joint constraints of the planetary boundaries for nitrogen flows, freshwater change, land system change and biosphere integrity (including protection of remaining forests), while reserving current agricultural areas for meeting the growing global demand for food, fodder and fibre. We find that the constrained BECCS potential from dedicated Miscanthus plantations is close to zero (0.1 gigatons of carbon dioxide equivalents per year under mid-century climate for Representative Concentration Pathway (RCP) 4.5). The planetary boundary for biosphere integrity has the largest individual effect, highlighting a particularly severe trade-off between climate change mitigation with BECCS and ecosystem preservation. Ultimately however, the overall limitation results from the joint effect of all four planetary boundaries, emphasizing the importance of a holistic consideration of Earth system stability in the context of climate change mitigation.
