Management of an Aquatic Invasive Weed with Uncertain Benefits and Damage Costs: The Case of Elodea Canadensis in Sweden

The invasive aquatic weed Elodea canadensis (Mich) (Canadian pondweed) might provide benefits for nature and society when present in low abundance by contributing to nutrient regulation in lakes, particularly in more degraded environments where native species are unable to persist, but can cause damage when it forms extensive monocultures that choke lake littoral zones. Using a bioeconomic model developed to describe the population dynamics and uncertain spatial dispersion of the weed in Lake Löt in Sweden, we conducted an analysis of optimal management of the species as regards good and bad effects on society. A theoretical finding was that the level of control required depends on the benefits, damage costs, control costs, and uncertainty in dispersal of the weed. Lake Löt was chosen as the case because data on dynamics of the weed are available for this lake. The empirical results showed that the total net benefits were sensitive to inclusion of uncertainty and benefits of the species, but uncertainty had little effect on the level and timing of optimal control of the weed. However, the cost of no action with associated damage costs net of benefits of the weed proved to be considerably larger than the control costs, irrespective of inclusion of benefits and uncertainty.