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.