Figure 1
Preliminary greenhouse gas inventory results for 2023: Forest land has turned into an emission source because the carbon sink of trees no longer cover emissions from forest soil
According to preliminary greenhouse gas inventory, the Land Use, Land-Use Change and Forestry (LULUCF) sector remained an emission source in 2023. The carbon sink of forest land has also become an emission source because the carbon sink of the growing stock no longer cover emissions from forest soil.
The net carbon sink in the LULUCF sector has decreased since 2010, and the sector turned into a source of emissions in 2018 (Figure 1). The transformation of the LULUCF sector from a net sink into an emission source can be explained by increased harvesting, higher carbon dioxide emissions from peat forest soils and the depletion of the carbon sink in mineral forest soil. According to the most recent inventory, the LULUCF sector was an emission source of 11.8 million tonnes of carbon dioxide equivalent (Mt CO2 eq) in 2023.
The most recent data on forest resources in Finland, measured in 2019–2023 (the 13th National Forest Inventory, NFI13), have been used in the inventory. Since the data on forest resources used in the calculation have become more accurate compared to the previous inventory, the results of years prior to 2023 have also been recalculated. For example, due to the recalculations the emissions of the LULUCF sector for 2022 changed from 4.44 Mt CO2 eq in the previous inventory to current 12.01 Mt CO2 eq.
Forests as emission sources from 2021
Of the land use categories, also forest land has become an emission source (Figure 2). According to the previous inventory as well, the net carbon sink in forests decreased as a trend, while forests remained a carbon sink for the whole time series beginning in 1990. According to the most recent inventory, forests became emission sources in 2021.
In 2023, the net emissions from forests were 1.12 Mt CO2 eq. The annual increment of the growing stock still exceeded the drain (harvest removals and natural drain), and thus the growing stock remained a carbon sink but were no longer sufficient to cover the growing emissions from forest soil.
Harvested wood products was the only category in the LULUCF sector that remained a net sink in 2023. The carbon sink in harvested wood products halved from 2022 to -1.7 Mt CO2 eq.
Forests have become emission sources because:
- Growth of the total tree biomass (leaves, branches, stems, roots) has decreased.
- Harvest removals have increased.
- Roughly 90 per cent of tree growth is lost through harvest removals and natural drain, while the corresponding figure was only slightly more than 70 per cent at the beginning of the 2010s.
- Carbon dioxide emissions from soil have increased, and increase of the carbon stock in mineral soil has stopped.
- Global warming has increased decomposition, and the growing stock has produced less new litter.
Figure 2
Decreases in the number of livestock reduced emissions in the Agriculture sector
Emissions in the Agriculture sector (6.0 Mt CO2 eq) decreased by one per cent in 2023 compared to 2022 (Figure 3). The decreased number of ruminants, including cattle, sheep and reindeer, reduced emissions. The number of pigs also decreased from 2022. This reduced emissions from enteric fermentation and manure management.
In the most recent inventory, emissions from liming and fertilising are based on 2022 data, as 2023 data are not yet available. Fertilisation emissions were significantly lower in 2022 than in previous years. The probable reason for this is the decreased use of fertilisers due to their higher prices. It is estimated that more fertilisers were used in 2023, and therefore emissions in the agricultural sector in 2023 will be higher in the final results to be published in March 2025.
Several changes were made in the calculation methods applied to the agricultural sector last year, which address the most recent scientific data and present improvements in estimated emissions from manure management and agricultural soils. The inventory has also used new peat soil data which makes it possible to more accurately identify peat fields and improves the calculation of organic farmland areas.
Figure 3
Why is methodological development carried out under the greenhouse gas inventory, even though it may change the results of previous years?
- Methodologies for the greenhouse gas inventory are guided by the guidelines of the Intergovernmental Panel on Climate Change (IPCC), as well as the European Union, which requires its member states to use more accurate methods in the calculation of greenhouse gas emissions.
- By developing calculation methods, the inventory can take new research results into account.
- Although more specific data and methods may increase or reduce previously reported emissions, methodological development is important so that climate actions can be targeted correctly and their impacts can be monitored as closely as possible.
- When calculation methods or source data improve, the entire time series must be recalculated for the most recent inventory from 1990 onwards. This may change the results of previous years.
Details of the calculation of the LULUCF sector’s emissions
- The LULUCF sector was an emission source of 11.8 Mt CO2 eq in 2023 (Figure 1).
- The net emissions of the LULUCF sector were 0.2 Mt CO2 eq lower than in 2022, but as a result of the recalculation of the inventory time series, the estimated net emissions for 2022 are now 7.6 Mt CO2 eq higher than in the previous inventory (Figure 1).
- The results of the inventory time series are recalculated when data or calculation methods are updated (Figures 1 and 2). In the most recent inventory calculation, the most significant change in the latest years of the time series comes from the updated tree biomass conversion factors.
- Biomass conversion factors are used to convert the stem volume of the growing stock into biomass. They are calculated based on the National Forest Inventory’s (NFI) tree-level data. The higher the biomass conversion factor, the greater the amount of leaf, branch, stem and root biomass relative to the stem volume.
- The biomass conversion factors calculated based on the most recent NFI13 data measured in 2019–2023 are smaller than those calculated based on the NFI12 data. In addition, the factors of the growing stock have decreased more than those of felled and naturally died trees.
- The lower tree biomass conversion factors can be explained by the change in the relative abundance of the tree age/size categories (there are relatively fewer young age groups/small size categories) and the change in tree crown ratio (crowns are shorter relative to tree length).
- Forests were a net emission source of 1.12 Mt CO2 eq in 2023 (Figure 2). The difference between tree growth and drain yielded a net carbon sink of -13.2 Mt CO2 eq, while total soil emissions were higher than this.
- Compared to the 2022 results, forest emissions were 1.6 Mt CO2 eq lower. In the recalculation, the 2022 results changed from a carbon sink of -4.8 Mt CO2 eq to emissions of 2.7 Mt CO2 eq (Figure 2).
- In the previous inventory, forests were a net carbon sink throughout the time series starting from 1990, but according to the recalculations, forests have been emission sources since 2021 (Figure 2). In the recalculation, the biomass conversion factors were updated from the NFI13 data and their multiplier effects on carbon balances of trees and soil changed the results of forests the most. The 2022 increment of growing stock decreased only slightly: from 103.3 m3 to 103.0 m3.
- According to the recalculation, trees sequestered 5.1 Mt CO2 eq and mineral soils 5.4 Mt CO2 eq less carbon than according to the previous inventory, whereas from the growing stock released 2.3 Mt CO2 eq (through harvest removals and natural drain) and peatlands 0.7 Mt CO2 eq less carbon than were estimated previously.
- According to the recalculation, mineral soils also turned into emission sources in 2021 and generated emissions of 0.37 Mt CO2 eq in 2023 (Figure 2). The long-term change in the carbon sink in mineral soils from -10 Mt CO2 eq at the beginning of the 2000s into an emission source can be explained by the decrease in the litter input generated by the growing stock (both in absolute terms and relative to increased carbon stocks) as well as global warming.
- In addition to net emissions from forests, the total emissions of other land use categories (cropland, grassland, wetlands, settlements) were 12.4 Mt CO2 eq in 2023 (Figure 1). Only harvested wood products were a carbon sink in 2023: harvested wood products were a sink of -1.7 Mt CO2 eq, half of the sink in 2022 (Figure 1).
Details of the calculation of the agricultural sector’s emissions
- Various improvements have been made to the calculation methods applied to the agricultural sector after the 2022 inventory:
- Updated the calculation of enteric methane and nitrogen excretion in pigs;
- Adopted the IPCC 2019 refinement in the calculation of emissions from manure management and agricultural soils;
- Updated manure system and management data on the basis of the manure survey conducted for producers;
- Harmonised the calculation of nitrogen emissions from agriculture with the reporting of ammonia emissions and other air pollutants;
- Updated the calculation of nitrogen excretion in horses;
- Adopted new peat soil data in the calculation of organic agricultural lands (also affecting the LULUCF sector).
- The broader adoption of the IPCC 2019 refinement marks the most significant improvement. The refinement takes into account scientific data generated after adoption of the 2006 guidelines and includes improvements to estimated emissions from manure management and agricultural soils, including the calculation of emissions from agricultural soils adapted to different climate zones.
- According to the recalculation, the methodological updates increased the agriculture sector’s total emissions by one to six percent, with the exception of 2022 (Figure 3). While the estimated emissions of inorganic fertilisers and manure management increased, those of manure application and grazing decreased.
- According to new peat soil data, the area of agricultural peat soils in Finland is higher than previously estimated, but contrary to previously estimated, a larger part of the area is used for perennial grassland production. Because emissions from perennial grassland cultivation are lower compared to annual crop cultivation, emissions from peatland cultivation changed only slightly.
