Forests are often called the lungs of the Earth – for a good reason. Trees produce oxygen and bind carbon dioxide. Growing forests absorb carbon from the atmosphere, storing it in wood biomass. When trees are harvested, carbon is transferred to wood-based products. At the end of the product’s lifecycle, the carbon is released into the atmosphere for new generations of trees to absorb. In order to sustain this cycle, a new tree has to be planted to replace every harvested one. Sustainably managed forests act as a carbon sink while yielding raw material to replace fossil resources.
We mitigate and adapt to climate change
Our climate commitment
-65%
Reduction of our own CO2 emissions
-30%
Reduction of our supply chain CO2 emissions
Pioneer climate-positive products
Keep forests as carbon sinks
Sustainably managed forests and plantations are carbon sinks
We plant 44 million seedlings per year. Forest regeneration after harvesting is the cornerstone of our sustainable forest management approach. Our actions do not result in any deforestation.
We carefully plan our harvesting rates to ensure that our forestry practices are fully sustainable. In short, we plant more trees than we harvest, and safeguard valuable habitats.
We manage our forests to help them serve as carbon sinks. We conduct ongoing research with expert partners to better understand and identify the climate impact of our forests.
For purposes of national greenhouse gas inventories, emissions are expressed as teragrams of CO2 equivalent. One teragram is equivalent to one million metric tons (Mt CO2 eq).
Finland: Sink = trees increment - drainage (harvesting and natural) + soil sink (using Yasso07). Uruguay: Sink = trees increment - drainage (harvesting) + soil sink (using Yasso07). USA: Source = change in tree carbon stock.
We aim to constantly improve and harmonise methodologies and make calculations more accurate. In 2024, calculation method for Uruguay was changed according to the recommendation by researchers. The previous year's figure is therefore not comparable (5-year averages are updated along with the new methods). See the full method descriptions below.
Carbon sink calculations in Finland,
the USA and Uruguay
The Natural Resources Institute Finland (LUKE) calculates the carbon sink of our own and leased forests and tree plantations in Finland, the USA and Uruguay. The results are reported annually as a five-year average and the calculation methods are developed as best practice evolves.
Changes in forest carbon stocks encompass both the trees and the soil. The calculation has utilized long-term measurement data from the Natural Resources Institute Finland (Luonnonvarakeskus) and mathematical modeling. Changes in the tree carbon stock have been determined as the difference between annual growth and removals. The calculation has been performed separately for forests growing on mineral soils and peatlands. The estimate of tree growth is based on the national forest inventory (Natural Resources Institute Finland, VMI), where the inventory cycle lasts five years. In the calculation, VMI growth figures for the years 2019–2023 have been used, with growth representing the average growth over the preceding five-year period prior to measurement. The VMI calculations were carried out on test plots from UPM’s lands, which included both forest and other wooded land. Harvest volumes and their allocation between mineral soils and peatlands have been obtained from UPM’s statistics. Harvest volumes from previous years have been scaled to the current forest land area to enable comparison. In addition, the amount of wood removed during harvesting has been supplemented with an estimate of natural mortality, based on average figures calculated by VMI for Southern Finland.
For mineral soils, changes in the soil carbon stock have been calculated using the Yasso07 model (Tuomi et al. 2011, en.ilmatieteenlaitos.fi/yasso), which describes the decomposition of logging residues in the soil and the consequent release of carbon dioxide. The inputs for the model calculations are the logging residue input to the soil, calculated from forest data, along with weather data that affect the decomposition rate.
For drained peatlands, the soil greenhouse gas balance has been calculated using the emission factors employed in the greenhouse gas inventory (preliminary data from the NID 2023 greenhouse gas inventory to be published in spring 2025) and the area. These emission factors are based on a comprehensive dataset of measurements conducted throughout Finland at various growing sites, as well as published research. The factors vary according to the growing site, the type of peat layer, and the drainage conditions. The calculated carbon dioxide, methane, and nitrous oxide emissions from drained peatlands have been adjusted computationally to correspond to the greenhouse gas impact of carbon dioxide.
Soil carbon stocks change slowly, which is why soil calculations are updated only every few years, in contrast to the more frequently updated tree data.
Literature references:
Natural Resources Institute Finland VMI (in Finnish): https://www.luke.fi/tietoa-luonnonvaroista/metsa/metsavarat-ja-metsasuunnittelu/metsavarat/
Tuomi, M., Laiho, R., Repo, A., & Liski. J. 2011. Wood decomposition model for boreal forests. Ecological Modelling 222 (3): 709-718. doi:10.1016/j.ecolmodel.2010.10.025
Statistics Finland 2023 preliminary data: “The 2023 greenhouse gas emissions decreased by 10% compared to the previous year” | Tilastokeskus
Carbon sinks on UPM-owned forests in the USA were calculated as the difference in carbon stored in growing stock between two time points in 5 years. The calculation complied with IPCC guidelines and was based on available data on annual totals of stem volumes by age classes.
The total biomass carbon stock change was based on species-specific wood densities (Wood database) and species group-specific biomass expansion factors (IPCC guidelines). The wood database was used because IPCC categories do not cover all tree species growing in UPM forests.
To convert expanding merchantable stem volume to above-ground biomass, we merged growing stock levels (m3) to correspond to the groupings appearing in IPCC guidelines. The age classes were merged to group levels of m3 in five groups. We summed these groups as per species groups in line with existing BCEFs (biomass carbon expansion factors) (hardwoods, pines, conifers, other) on a per-year basis. The group “other” was presumed to have average BCEFs (biomass carbon expansion factors) for hardwoods, pines, and conifers. The calculated species groups’ above-ground biomasses were converted to carbon using constants appearing in table 4.3 in the IPCC guidelines.
The below-ground tree biomass was calculated based on ratios between above-ground and below-ground biomasses for specific species groups in compliance with IPCC guidelines (Table 4.4.). Annual above- and below-ground forest carbon sinks were summed up per year and converted to CO2 by multiplying by the ratio of the molecular weight (44/12 from C to CO2). The difference between each year was then calculated. Currently soil carbon stock is not included in the calculations.
Literature:
Wood database: https://www.wood-database.com/
IPCC guidelines Volume 4: https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol4.html
The calculation of changes in forest carbon stock, or the forest carbon sink, is based on annual growth (increment) and removals due to harvesting (drain). The calculation follows IPCC guidelines and relies on data provided by UPM, including annual stem volumes, growth data, land area datasets, and harvesting volumes.
The volume is converted into biomass using species-specific densities and biomass expansion factors (BEF) (Hirigoyen et al., 2021). The carbon content of the biomass is assumed to be 50%, and carbon is converted to carbon dioxide using the factor 44/12.
In the Increment-Drain method, tree growth (increment) is calculated using annual volume growth and BEF factors, including the bark portion of the tree. The forest removal (drain) is determined based on harvesting data. The net carbon sink, which represents the annual change in the forest carbon stock, is obtained as the difference between growth and removals. The calculation includes cultivated eucalyptus species Eucalyptus dunnii and Eucalyptus grandis.
Changes in soil carbon stock are calculated using the dynamic Yasso07 soil model (Tuomi et al. 2011, Finnish Meteorological Institute), which simulates carbon decomposition and changes up to a depth of 1 meter. The modeling is based on the amount and quality of litter input as well as local weather conditions. The methodology is continuously being developed in collaboration with the Natural Resources Institute Finland (LUKE).
Litter input is estimated plot-specifically for the entire rotation period of the forest stand. The tree volume of previous rotations is calculated based on UPM's growth models, and the plantation's rotation period is assumed to be 11 years. Litter input is estimated for different tree parts (trunk, leaves, branches, roots) using species-specific and general conversion factors.
Daily temperature and precipitation data are obtained from meteorological stations across Uruguay, maintained by INIA (National Agricultural Research Institute of Uruguay).
Both tree and soil calculations are carried out separately for eucalyptus plantations owned and leased by UPM. The annual carbon sink is reported as the sum of plot-specific carbon sink values, considering both growth and the impact of harvesting on the forest carbon stock.
Literature references:
Hirigoyen, A., Resquin, F., Navarro-Cerrillo, R., Franco, J., & Rachid-Casnati, C. (2021). Stand biomass estimation methods for Eucalyptus grandis and Eucalyptus dunnii in Uruguay. BOSQUE, 42(1), 53–66. https://doi.org/10.4067/S0717-92002021000100053
IPCC guidelines Volume 4: https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol4.html
Tuomi, M., Laiho, R., Repo, A., & Liski. J. 2011. Wood decomposition model for boreal forests. Ecological Modelling 222 (3): 709-718. doi:10.1016/j.ecolmodel.2010.10.025
Replacing fossils with wood-based products
Wood has enormous potential as a renewable, recyclable and carbon-neutral raw material. We foresee an exciting future for innovative wood-based products in the post-fossil era.
Sustainable wood-based products start with sound forestry practices. Our forests serve as carbon sinks thanks to our sustainable harvesting and systematic forest regeneration policy. A forest’s total carbon sequestering capacity also includes the carbon contained in the soil. Finland’s peatlands, for instance, are massive carbon storages. Protecting natural peatlands is therefore important both for the climate and for biodiversity.
The efficient use of wood raw material is an important factor affecting the carbon footprint of wood-based products. We maximize the usage of harvested wood by harnessing by-products and side streams. A great example is our renewable diesel made of crude tall oil, which is a by-product of pulp manufacturing.
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