Communities are often faced with large and intractable problems that seem to be outside of their control. For example, water and air quality are critical for health and environmental justice, yet as complex systems they seem difficult to influence. Thinking big can be overwhelming--there are many actors, shifting conditions, incomplete knowledge, and unclear jurisdictions. This session will discuss how community actions can overcome these problems and leverage local sustainability to shift large-scale systems. Two case studies will be presented where ongoing grassroots community action has made real changes within large-scale systems affecting water and air quality. Instead of becoming frustrated with partial effectiveness, these communities demonstrate how to authentically and effectively organize aggregated action.