ARE student François Castonguay presented his research on ecological interventions. Ecological interventions that prevent and manage environmentally transmitted diseases are receiving increasing interest by both researchers and practitioners. When profit maximization is the sole goal of an entity that undertakes ecological interventions, additional social benefits may be lost. In this paper, François investigates the consequences that profit-maximizing behavior has on the transmission of environmentally transmitted diseases. He simulates the behavior of an aquaculture farmer whose activity (e.g., prawn aquaculture) has the potential to create positive externalities on disease prevalence (e.g., reduction in the intermediate hosts’ population). François finds that the decisions of a profit-maximizing aquaculture farmer can mitigate, if not eliminate, this positive externality. The results suggest that it may be necessary for policymakers to incentivize aquaculture farmers in order to reap any indirect societal benefits from their activity.