Quantifying Earth system interactions for sustainable food production: an expert elicitation

Abstract

Several safe boundaries of critical Earth system processes have already been crossed by human perturbations. Recent research indicates that not accounting for the interactions between these processes may further narrow the safe operating space for humanity. Yet existing work accounts only for transgression of single boundaries and only a few studies take some of the boundary interactions into account. For future sustainability assessments, it is essential to understand boundary transgressions and their interactions more comprehensively. Here, we explore quantitatively how strongly seven variables, representing Earth system processes relevant to food production, interact with each other, using a structured expert knowledge elicitation. We identify Green water and Land system change as crucial interactive processes through their impacts on multiple relevant processes, while Biosphere integrity-land, freshwater and ocean components appear to be most affected by other Earth system processes, most notably Blue water and Biogeochemical flows. The elicitation also enabled us to map the complex network of mechanisms mediating interactions, to support integrated Earth system and planetary boundaries modelling and assessments. Finally, we created a prioritisation scheme for future research according to the interaction strengths and existing knowledge gaps. Our analysis improves our understanding of Earth system interactions, with clear implications for sustainable use of natural resources such as the biophysical limits for food production.

Global water cycle shifts far beyond pre-industrial conditions – planetary boundary for freshwater change transgressed

“…Although it is likely that buffers in the Earth system allow for greater variability in the water cycle compared to the pre-industrial period, the precautionary principle of the PB framework (8) motivates a conservative placement of the new PB for freshwater change at the lower level of scientific uncertainty. We consider this to be at the upper end (95 th percentile) of pre-industrial variability range, which can be regarded as highly precautionaryalthough an even stricter boundary placement could also be justified, due to signs of weakened Earth system resilience (20) and the complex interactions between freshwater and other PBs (35).…”

“…Although impacts of freshwater change on the Earth system functions of freshwater have been studied extensively at local to regional scales (1), regional to planetary scale assessments of impacts are still lacking. Furthermore, the PBs' control variablesincluding freshwaterinteract strongly with each other, which should be considered when setting a PB for freshwater change (35). These factors complicate the boundary setting, as ideally, PBs should be set based on control variable-response variable relationships to minimize the risk of abrupt or irreversible state shifts.…”