Assessing historical and potential future Planetary Boundary transgressions in a consistent modelling framework

In an attempt to define a safe operating space for humanity, the Planetary Boundary (PB) framework proposes precautionary limits to human interference with nine critical Earth system processes. However, quantitative assessments of these limits and past, present or potential future statuses and transgressions of PBs are (i) inflicted by differences in definitions, data and models used and (ii) require process-based models of the Earth system in the absence of globally available observational datasets on the PB control variables. To advance such process-based and consistent PB quantifications for terrestrial PBs (land system change, biosphere integrity, freshwater change, biogeochemical flows), we developed an R based software package, “boundaries”, for calculation and visualization of PBs based on outputs from the global terrestrial biosphere model LPJmL. The coupled, spatiotemporally explicit and dynamic simulation of the biogeochemical processes underlying the control variables in LPJmL allows for calculation of the temporal evolution of PB statuses, i.e. if, where and how strongly boundaries are transgressed, at different scales (for both planetary and corresponding subglobal boundaries from regional to grid cell scale).

Next to a short technical overview on boundaries and its structure, the poster shows calculated current spatially-explicit statuses of the four PBs considered as well as their simulated evolution during past decades, based on one consistent modelling framework and applying the latest PB definitions. In addition to contributing to a better understanding of temporal trajectories, spatial patterns and drivers of PB transgressions, boundaries can be applied to evaluate future scenarios in terms of their PB impacts and potentials to return to a safe space within PBs. As one potential critical PB trade-off, the poster focuses on different land-based carbon dioxide removal (CDR) strategies for reducing pressures on the climate change PB. The scenarios’ results show the importance of dietary changes towards less livestock products to release pasture areas for CDR. If forests can be restored on spared land, pressures on multiple PBs could be synergistically alleviated.