Understanding the complementary linkages between environmental footprints and planetary boundaries in a footprint–boundary environmental sustainability assessment framework

While in recent years both environmental footprints and planetary boundaries have gained tremendous popularity throughout the ecological and environmental sciences, their relationship remains largely unexplored. By investigating the roots and developments of environmental footprints and planetary boundaries, this paper challenges the isolation of the two research fields and provides novel insights into the complementary use of them. Our analysis demonstrates that knowledge of planetary boundaries improves the policy relevance of environmental footprints by providing a set of consensus-based estimates of the regenerative and absorptive capacity at the global scale and, in reverse, that the planetary boundaries framework benefits from well-grounded footprint models which allow for more accurate and reliable estimates of human pressure on the planet's environment. A framework for integration of environmental footprints and planetary boundaries is thus proposed. The so-called footprint–boundary environmental sustainability assessment framework lays the foundation for evolving environmental impact assessment to environmental sustainability assessment aimed at measuring the sustainability gap between current magnitudes of human activities and associated capacity thresholds. As a first attempt to take advantage of environmental footprints and planetary boundaries in a complementary way, there remain many gaps in our knowledge. We have therefore formulated a research agenda for further scientific discussions, mainly including the development of measurable boundaries in relation to footprints at multiple scales and their trade-offs, and the harmonization of the footprint and boundary metrics in terms of environmental coverage and methodological choices. All these points raised, in our view, will play an important role in setting practical and tangible policy targets for adaptation and mitigation of worldwide environmental unsustainability.