Carbon budgets in northern Swedish Forests, 1800-2013

Abstract: Forests and forest management can mitigate increased carbon dioxide (CO2) concentrations in the atmosphere through sequestration of carbon and/or substitution. A major question has been whether it is better to use or conserve forests, with some claiming that European forests carry a huge carbon debt as a result of forestry. The overall aim of this study was to quantify a baseline for the total carbon stock in the pre-industrial forest (PIF) (1800-1850) for the two northernmost counties in Sweden, Västerbotten and Norrbotten, and the carbon stock development until 2013. The total carbon storage in the forest was divided into three carbon pools, including above and below-ground biomass, soil, and deadwood. Also, the carbon sequestered in the harvested wood product (HWP) pool was estimated and added to the analysis. The estimated pre-industrial forest state was based on existing studies of forest history and inventory data from areas with no or limited impact of forestry. From 1923, inventory data from the national forest inventory (NFI) were used. The concept of climate change mitigation efficiency (CCME) was applied to describe the total effect of forest use, i.e. the average avoided and reduced CO2-emissions per cubic meter of harvested biomass. A sensitivity analysis was conducted on different levels of wood storage in the pre-industrial forest and altered soil carbon accumulation rate and substitution effects were analyzed. The results showed that a carbon debt had occurred largely during the 19th century and had been repaid in 2001. The carbon debt payback time was almost 100 years but could have been faster with a product use strategy resulting in higher CCME. The sensitivity analysis shows that the above ground carbon stock in the PIF, had the largest impact on the size of the carbon debt. It also confirms that the carbon debt was of a temporary character and has most likely been repaid. The present trajectory of the forest sectors carbon balance in the study area outlines that active forest management increases carbon stocks in the forests and forest-based products. While allowing for substitution of fossil-based products and energy-intensive materials. Consequently, climate change is mitigated since the buildup of CO2 concentration in the atmosphere is countered due to the carbon sink in the forest, HWP and the substitution effect from the use of forest products.