Abstract for: Managing Chronic Wasting Disease with System Dynamics

Chronic Wasting Disease (CWD) is a fatal prion disease of cervids affecting nearly 2/3 of US states. Disease management is complex due to diverse stakeholder interests, limited agency resources, and uncertainty about key mechanisms. We developed a System Dynamics model to support Wisconsin's 15-year CWD management plan update, and subsequently measure unobserved system features and assess historic policy efficacy. Beginning with expert elicitation, and following Structured Decision Making methodology, stakeholders generated alternative actions and metrics of interest. Simulations mapped the effects of each action on their metrics, providing visual and quantitative summaries of performance along each dimension, allowing stakeholders to weigh outcomes via their preferred metrics. Inclusion of the model in the stakeholder process provided a consistent structure for discussion and focused effort on important leverage points, avoiding conflict. To refine policy recommendations, uncertainty in key features of the system like the role of density dependence or environmental sources in disease transmission and the effect of carrying capacity feedbacks on vital rates were investigated with Bayesian inference integrating detailed data with priors from literature. Links between model structures and key parameter estimates were revealed. CWD management has many of the hallmarks of classic SD policy interventions. Misperceptions of feedback and diverse interests confound stakeholder interactions. Policies trigger resistance from the system. Complex structure, nonlinearities and pervasive uncertainty complicate communication of progress. Long delays and compensating feedback previously concealed benefits of historic management actions. While the disease is intractable, performance improvement is possible.