Introduction: Why citizen science? / Janis L. Dickinson and Rick Bonney -- The practice of citizen science. Overview of citizen science / Rick Bonney and Janis L. Dickinson ; Projects and possibilities : lessons from citizen science projects (From backyard observations to continent-wide trends : lessons from the first twenty-two years of Project FeederWatch / David N. Bonter ; Monitoring monarchs : citizen science and a charismatic insect / Karen S. Oberhauser ; Neighborhood Nestwatch : mentoring citizens in the urban matrix / Peter P. Marra and Robert Reitsma ; Project BudBurst : citizen science for all seasons / Sandra Henderson, Dennis L. Ward, Kirsten K. Meymaris, Paul Alaback, and Kayri Havens) ; Using bioinformatics in citizen science / Steve Kelling ; Growing the base for citizen science : recruiting and engaging participants / Miyoko Chu, Patricia Leonard, and Flisa Stevenson ; What is our impact? Toward a unified framework for evaluating outcomes of citizen science participation / Tina Phillips, Rick Bonney, and Jennifer L. Shirk -- Impacts of citizen science on conservation research. The opportunities and challenges of citizen science as a tool for ecological research / Caren B. Cooper, Wesley M. Hochachka, and André A. Dhondt ; Widening the circle of investigation : the interface between citizen science and landscape ecology / Benjamin Zuckerberg and Kevin McGarigal ; Using data mining to discover biological patterns in citizen science observations / Daniel Fink and Wesley M. Hochachka ; Developing a conservation research program with citizen science / Ralph S. Hames, James D. Lowe, and Kenneth V. Rosenberg ; Citizens, science, and environmental policy : a British perspective / Jeremy J.D. Greenwood -- Educational, social, and behavioral aspects of citizen science. Cognitive considerations in the development of citizen science projects / Rebecca C. Jordan [and others] ; Who poses the question? Using citizen science to help K-12 teachers meet the mandate for inquiry / Nancy M. Trautmann [and others] ; A gateway to science for all : celebrate urban birds / Karen Purcell, Cecilia Garibay, and Janis L. Dickinson ; Children and nature : following the trail to environmental attitudes and behavior / Nancy M. Wells and Kristi S. Lekies ; Internet-based social networking and collective action models of citizen science : theory meets possibility / Heather A. Triezenberg [and others] ; A role for citizen science in disaster and conflict recovery and resilience / Keith G. Tidball and Marianne E. Krasny. In Citizen Science, experts from a variety of disciplines share their experiences of creating and implementing successful citizen science projects, primarily those that use massive data sets gathered by citizen scientists to better understand the impact of environmental change. This first and foundational book for this developing field of inquiry addresses basic aspects of how to conduct citizen science projects, including goal-setting, program design, and evaluation, as well as the nuances of creating a robust digital infrastructure and recruiting a large participant base through communications and marketing. An overview of the types of research approaches and techniques demonstrates how to make use of large data sets arising from citizen science projects. A final section focuses on citizen science's impacts and its broad connections to understanding the human dimensions and educational aspects of participation. Intended as a resource for a broad audience of experts and practitioners in natural sciences, information science, and social sciences, this book can be used to better understand how to improve existing programs, develop new ones, and make better use of the data resources that have accumulated from citizen science efforts. Its focus on harnessing the impact of "crowdsourcing" for scientific and educational endeavors is applicable to a wide range of fields, especially those that touch on the importance of massive collaboration aimed at understanding and conserving what we can of the natural world.