Assessing economic benefits and costs of carbon sinks in boreal rotation forestry

We study the optimal enhancement of forest carbon sinks via forest management changes in boreal even-aged Scots pine (Pinus sylvestris) forests. The economic–ecological stand-level optimization model integrates a statistical–empirical individual-tree growth model with a comprehensive model for carbon in living trees, wood products, and soil. We use reinforcement learning to optimize for rotation length, thinning timing, and thinning intensity. Carbon dioxide (CO2) pricing has a notable effect on the optimal solutions and on the corresponding CO2 flows and carbon stocks. Under a 1% interest rate, increasing the CO2 price from zero to €100 increases the discounted carbon sink by 83% and the total steady-state carbon stock by 122%. Increasing the CO2 price decreases the economic significance of thinning, and, with a high enough CO2 price, the stand is harvested only with clear-cuts, which are further postponed by CO2 price increases. Decreasing stand volume or total C stock cannot be taken as a sign of an overly mature stand. Depending on the CO2 price and interest rate, the economic benefit–cost ratio of additional carbon sinks via forest management changes varies between 1.9 and 3.7. Overall, the results reveal a high potential to increase the role of boreal managed forests in climate change mitigation.