We are pleased to introduce the second special issue from Challenges in Sustainability, this time as a part of the Taskforce on Conceptual Foundations of Earth System Governance, an initiative by the Earth System Governance Project (ESG) (http://www.earthsystemgovernance.net/conceptual-foundations/). The ESG Project is a global research alliance. It is the largest social science research network in the field of governance and global environmental change. ESG is primarily a scientific effort but is also designed to assist policy responses to pressing problems of earth system transformation.