Managing Systems with Non-convex Positive Feedback

We study here optimal management of dynamic ecological systemsthat exhibit a destabilizing positive feedback. The prototypeexample is that of a shallow lake in which phosphorous loadingplaced by anthropogenic activities (fertilizers for farmingand gardening) is stored in sediments until a critical levelis reached after which there is a destabilizing return to thewater – the tradeoff between farming interests and lake qualitygenerates an optimal control problem. We show that in such systems, there may be a variety of local optima and associatedbasins of attraction wherein the optimal path may depend onstarting state (phosphorous stock). We characterize the variouspossible optimal behaviors and identify the ambiguities thatcan only be resolved by choice of functional form.