Optimal rotation with differently-discounted benefit streams

The case is often now made that discount rates should decline with time. Underlying reasons include that some kinds benefit (or cost) might be discounted at a lower rate than that used for others: in particular, that rates for carbon values and environmental amenities might be less than that for timber. A lengthening sequence of rotations then arises, whether the benefits are consumptive ones realised at the rotation end, or non-consumptive ones whose annual value increases through the rotation. A timber discount rate lower than that for non-consumptive benefits leads to a shortening sequence of rotations. The results differ importantly from those of discounting all benefits and costs at a reducing rate through time.