Cooperation, Spatial-Dynamic Externalities, and Invasive Species Management

Most terrestrial biological invasions occur in landscapes comprising numerous, independently managed properties. Thus, control of invasion spread generally depends on the choices of many managers, each deciding the extent to control invasions on their property. Here we develop a spatially-explicit, integrated model of invasion spread and human behavior to examine how people’s control choices under laissez-faire affect patterns of invasion spread and the total costs and damages imposed by an invader. We evaluate how characteristics of the bioeconomic and social system, including the extent of cooperation among managers, affect the divergence between socially optimal and private control efforts. We find that system-wide invasion externalities generally increase with the potential range size of an invader and with marginal damages from invasion and decrease with marginal control costs and with the size of the invasion when it is discovered. As expected, private control decisions tend to under-control the invasion relative to socially optimal control. However, we also find that less extensive cooperation is needed to control invasions whose costs and damages otherwise lead to the largest externalities. This novel finding suggests that even small amounts of cooperation can avoid some of the worst invasion outcomes and coordination of control can provide large social benefits. This research highlights the importance of human behavior for affecting invasion spread and economic outcomes.