Despite recent advancements in sustainability research, the study of the dynamics and prospects of co-evolving human and ecological systems, the discipline still lacks an overarching theoretical framework. Scenario analysis offers a promising integrative approach, and scenario methods have been improved by a wave of new studies. Still, these studies remain most compelling in their opening frames, where quantitative modeling can track unfolding trends, and their closing frames, where qualitative description can provide rich descriptions of long-term social visions. Not surprisingly, given the formidable uncertainties, the trajectories between now and then remain poorly specified, if addressed at all. This paper suggests ways of thinking about these pathways and pivots, the world lines through the terra incognita between current global realities and alternative futures.

Originally published in Ecological Economics 65, no. 3 (2008): 461-470.