A bioeconomic analysis of an emerald ash borer invasion of an urban forest with multiple jurisdictions

Bio-invasions occur in management mosaics where local control affects spread and damage across political boundaries. We address two obstacles to local implementation of optimal regional control of a bio-invasion that damages public and private resources across jurisdictions: lack of local funds to protect the public resource and lack of access to protect the private resource. To evaluate these obstacles, we develop a spatial-dynamic model of the optimal control of emerald ash borer (EAB) in the Twin Cities metropolitan area of Minnesota, USA. We focus on managing valuable host trees with preventative insecticide treatment or pre-emptive removal to slow EAB spread. The model includes spatial variation in the ownership and benefits of host trees, the costs of management, and the budgets of municipal jurisdictions. We develop and evaluate centralized strategies for 17 jurisdictions surrounding the infestation. The central planner determines the quantities of trees in public ownership to treat and remove over time, to maximize benefits of surviving trees net costs of management across public and private ownerships, subject to constraints on municipal budgets, management activities, and access to private trees. The results suggest that centralizing the budget across jurisdictions rather than increasing any one municipal budget does more to increase total net benefits. Strategies with insecticide treatment are superior to ones with pre-emptive removal because they reduce the quantity of susceptible trees at lower cost and protect the benefits of healthy trees. Increasing the accessibility of private trees to public management substantially slows EAB spread and improves total net benefit.