Balancing conservation and commerce: A shadow value viability approach for governing bycatch

The losses from extinction events are not well-known, making an expected net benefits approach to conservation problems difficult to implement. A viable control strategy instead focuses on limiting the risk of extinction to some acceptably low level at the least possible cost. Here we describe a shadow value viability approach for solving conservation problems with irreversible thresholds with dynamic programming. A social planner calculates the minimal (virtual) level of loss from extinction that would trigger sufficient action to avoid extinction with the desired confidence. The cost-effective policy then arises from acting as if the resulting shadow value is real. We demonstrate the method in a numerical application to the conservation of the Pacific leatherback turtle population, which co-mingles with the Pacific swordfish fishery. We show how the cost-effective outcome can be achieved among decentralized fishers by using the planner’s shadow value to set market-based instruments for managing turtle bycatch. This approach translates the species viability objective into economic terms so conservation and commercial harvest can be rationally integrated.