Earth 2020: Science, society, and sustainability in the Anthropocene.

April 22, 2020, marks the 50th anniversary of Earth Day and the birth of the modern environmental movement. As we look back over the past half century, we can gain significant insights into the evolving human imprint on Earth's biophysical systems, and the role of science and scientists in driving societal transitions toward greater sustainability. Science is a foundation for such transitions, but it is not enough. Rather, it is through wide collaborations across fields, including law, economics, and politics, and through direct engagement with civil society, that science can illuminate a better path forward. This is illustrated through a number of case studies highlighting the role of scientists in leading positive societal change, often in the face of strong oppositional forces. The past five decades reveal significant triumphs of environmental protection, but also notable failures, which have led to the continuing deterioration of Earth's natural systems. Today, more than ever, these historical lessons loom large as we face increasingly complex and pernicious environmental problems.