Ecosystem services are required to sustain human life and enhance its quality. Hence, environmental security must come from protecting and managing those services. Ecological risk assessment can predict and estimate effects of proposed actions, but it is insufficient alone for two reasons. First, it can fail because of inadequate application, unforeseen stressors, or unpredictable effects. Second, in many cases ecosystem services that sustain life are already impaired, resulting in reduced human welfare. For these reasons, environmental security requires the development of ecoepidemiology, a science that will identify impaired ecosystem services and determine the causes of impairment so that remediation and restoration can occur. A method for causal analysis, developed to identify causes of impairment in aquatic ecosystems, may provide a template that can be adapted to identify the causes of diminished ecosystem services and the resulting reductions in human welfare. Some of the challenges for adapting the existing method include explicitly defining ecosystem services required to sustain human life, appropriately matching the scale of the analysis to the ecological processes that deliver those services, and possibly customizing the logical considerations used in causal analysis. Advancing the science of ecoepidemiology holds the promise of helping scientists frame and guide rational debate, providing a sound basis from which to launch risk assessment and risk management scenarios, and ultimately informing environmental decision-making that affects human welfare, development and environmental security within acceptable risks.