Toward energy systems within the planetary boundaries.

Energy systems are essential for societal development but also contribute significantly to global environmental impacts. For the first time, a review explores the role of energy systems to transgression levels of planetary boundaries, based on quantitative sustainability assessments. The environmental sustainability of various energy sources is reviewed to identify key hotspots and describe pathways toward more sustainable alternatives. Fossil-based energy systems significantly contribute to exceeding planetary boundaries, remarkably, climate change, ocean acidification, and, to a lesser extent, chemical pollution and eutrophication. While renewable energy systems perform better in climate change and ocean acidification, they might lead to trade-offs in other categories. For instance, expansion of bioenergy could lead to increased pressures on biogeochemical cycles, water demand and land use. This review emphasizes the need for a holistic approach, integrating planetary boundaries into energy transition strategies to ensure sustainability and minimize environmental impacts.