Past environmental scholars have sought to explain why environmental mobilization succeeds or fails in reducing environmental hazards, but less scholarship has assessed why environmental mobilization occurs. To examine this question, we employ a month-level temporal model to predict the likelihood of a mobilization event taking place, and a network-analysis model that predicts the involvement of Social Movement Organizations (SMO’s). Our results indicate that, with the exception of anti-nuclear mobilization, the environmental movement saw demobilization effects from past events, most strongly for institutional events such as lawsuits. However, past SMO participation significantly increased the likelihood of a non-nuclear environmental protest occurring in the subsequent period. We also find that SMO’s prefer to participate in events which match their past experiences, have greater public participation, and target the government. These findings support resource mobilization theory by highlighting the positive influence that SMO’s have on mobilization formation and momentum as well as demonstrating how SMO participation shapes and is shaped by event characteristics. We conclude with a discussion of the implications of our results for the future of the environmental movement.