Complexities in the simple optimization of wood production and carbon sinks

To resolve several open issues in the forestry and carbon literature, we apply an analytically solvable stand-level model for optimizing the values of wood production and carbon sinks. We show that when stand volume development has a peak, locally optimal finite and infinite rotation periods may exist simultaneously. With infinite rotation period, forests are most valuable as a carbon storage, and this outcome is shown to depend on discount rate and, in specific situations, on initial stand age. Rotation periods maximizing the pure value of carbon sinks is proved to lengthen with discount rate. In contrast to existing understanding, zero discounting does not render carbon sink enhancement as superfluous; instead, maximizing the average carbon stock in standing forests and in harvested biomass is shown to become the long-run optimality criterion. However, combining carbon sinks with wood production implies that the role of carbon completely disappears when the discount rate approaches zero. The value of carbon sinks changes the rationale of stand value and its development over the rotation. Our results have far-reaching implications in interpreting various carbon sink studies.