Preface -- Acknowledgments -- Introduction -- An overview of the model -- Lessons and legacies -- The ecosystem concept in biology -- The roots of human ecology -- Key components and variables for analyzing human ecosystems -- Goals, strategies, and tactics for inquiry and action -- Using the model for science during crisis -- Revitalizing human communities and reclaiming biological communities : the Baltimore story -- Toward a more perfect civic order : lessons learned from research -- Extending the capability of the model -- Leaning forward : future challenges to human ecosystems -- Conclusion.