© 2016 Elsevier B.V. The transition from single-media, single-location, and single point-in-time analysis to a cumulative approach represents a profound challenge – and opportunity – for policy makers, planners, advocates and researchers. These challenges and opportunities are, in part, methodological (e.g., data availability of pollution sources, uncertainty of chemical reactions among multiple pollutants, evaluating combined health effects of multiple environmental stressors). However, the social complexity of this issue has been acknowledged, but not systematically documented and analyzed. As a result, there is a significant gap between the development of cumulative impacts analysis and a limited ability to reap their benefit in resolving environmental justice conflicts. Framing cumulative impacts as a “wicked problem” can help highlight some of the challenges in implementing such approaches and can point the way towards applying these approaches to improving collaboration between policy makers, planners, and advocates. We present two case studies of cumulative impacts analysis in California using socio-spatial mapping and public participatory geographic information system (PPGIS). These cases will illustrate the challenges and opportunities for combining quantitative and socio-spatial science with PPGIS as strategies to address the wicked nature of assessing and acting to address cumulative environmental impacts. The case studies will emphasize the value of an adaptive, participatory, and transdisciplinary approach as an effective response to the wicked qualities of cumulative impacts themselves. These cases can help planners, policy makers, and community advocates to apply a cumulative impacts approach to their own wicked problems.