Highlights ► Social capital accumulation can indeed make a difference to the level of sustainability that can be achieved. ► But that the types of governance and of networks available in communities also make a difference to LA 21 outcomes. ► There is an essential role for local government to play. ► Create an environment in which citizens empower themselves by collaboratively making the rules for participation.

Abstract Since the launch of LA 21 in 1992, local governments in many countries have been seeking to improve sustainability. Various studies have been conducted in the past two decades. A brief review of the literature reveals general progress in citizen participation and a shift from the agenda-setting stage to action, including the Cities and Climate Change Initiative (CCCI). However, the difficulty of taking a three-dimensional (environmental, economic and social) sustainability approach is being experienced in many places. Local communities are therefore adapting sustainable development to their individual context. Some past studies have investigated what influences local sustainability performance; this includes such factors as institutional capacity and the availability of community networks and champions in the public, private, and voluntary sectors. Drawing on their findings, this paper examines in particular the workings and effects of community networks in targeting sustainable development at the local level; it looks at three examples of current action towards sustainability in Japanese cities, focusing on social capital networks and the role local government is playing in the process. Investigating quantitatively whether social capital accumulation through citizen participation does in fact make a difference in the progress towards sustainability, and also examining qualitatively how it is possible to generate and make the most of social capital networks towards the same end, this paper concludes that social capital accumulation can indeed make a difference to the level of sustainability that can be achieved, but that the types of governance and of networks available in communities also make a difference to LA 21 outcomes. There is an essential role for local government to play: that is to (1) create an environment in which citizens empower themselves by collaboratively making the rules for participation, and (2) identify key individuals who connect the various networks and involve them in the development of sustainability strategies; thereby expediting the process of reaching the stage where local government and citizens share the same sustainability goals.