In an effort to develop "sustainability economics" Baumgärtner and Quaas (2010) neglect the central concept of environmental economics-"environmental externality". This note proposes a possible connection between the concepts of environmental externality and sustainability. In addition, attention is asked for other aspects of "sustainability economics", namely the distinction weak/strong sustainability, spatial sustainability and sustainable trade, distinctive sustainability policy, and the ideas of early "sustainability economists". I argue that both sustainability and externalities reflect a systems perspective and propose that effective sustainability solutions require that more attention is given to system feedbacks, notably other-regarding preferences and social interactions, and energy and environmental rebound. The case of climate change and policy is used to illustrate particular statements. As a conclusion, a list of 20 insights and suggestions for research is offered.
