The IHDP Open Meeting 2009 was the first one influenced by the IHDP Strategic Plan 2007-2015. It contributed successfully to the implementation of its pillars on cutting-edge science, capacity development and science-policy interaction. It provided the human dimensions research community with substantial food for thought, as well as many concrete research collaborations initiated during these days in Bonn. It clearly reasserted to the participants the importance of the human dimensions research agenda in times of rapid change and has motivated IHDP to implement this agenda. In 2009, the Open Meeting coincided with an unprecedented momentum for the social sciences and their expected contributions to a better understanding of the challenges of global change. As attention in science and policy is increasingly addressing and further understanding both the impacts of global change on the Earth System and the need to better understand possible response options and sustainability solutions, the social sciences can indeed offer significant contributions to these changes taking place. By shaping the conference agenda in the light of four major social challenges – demography, resources and technology, equity and sustainable adaptation, and institutions and governance – the conference provided the intellectual set-up for this important task.