Scientific understanding of environmental problems is increasingly rapidly, but often the best science is underutilized and policy responses are slow or inadequate. Ecology and other relevant disciplines are seen by some as unhelpful or even detrimental to progress in policy making, in part due to the increasing complexity of scientific understanding. The technical nature of scientific analysis has excluded much of the public from meaningful participation, in turn leading to exclusion of science from public deliberation. Reaffirming the salience of ecology in a pluralistic society requires meaningful public discourse that is informed by scientific understanding and the increasingly powerful tools used for analysis and planning.  Drawing on three applications of landscape assessment and planning in arid North America, we present a new model for participatory science to support policy development.  Drawing on quantitative techniques from the social sciences, we evaluate science-based forest planning efforts involving diverse citizens, ecologists, and decision makers. Results indicate that participation in data development and analysis informs and elevates public discourse, and that subsequent interaction among people holding divergent values and interests often leads to negotiated agreements and convergence during policy development.