Carbon balance in forests
When trees grow, they store carbon in their biomass. In this way, they are able to absorb large quantities of CO2 from the atmosphere. Conversely, when trees die or are harvested, their decomposition or burning releases the carbon stored in their biomass. As a result, sustainable forest management that also allows for sustainable carbon storage can help protect the climate. The use of durable wood products (e.g. construction timber, furniture) is another (temporary) method of storing carbon.
By ratifying the Kyoto Protocol, Switzerland agreed to record variations in forest carbon stocks generated by afforestation and deforestation (Art. 3.3) as well as forest management and wood use (Art. 3.4).
The areas of afforestation and deforestation are relatively small in comparison with the total forest area. Because growth in biomass through afforestation occurs slowly, whereas with deforestation, all timber is removed at once, the emissions generated by deforestation are significantly higher than sequestration as a result of afforestation. Consequently, under the terms of Article 3.3 there is a carbon source every year.
The carbon balance in forests is made up of CO2 absorption as a result of tree growth, changes in the CO2 stored in mulch, soil and deadwood, minus the losses resulting from forest management (harvesting) and natural outflows. Changes in carbon stocks in domestic wood products (harvested wood products, HWP) also have to be recorded. Except in years with severe storms, with increased losses of living biomass in the forest due to forced usage, and greater tree mortality in subsequent years (e.g. after ‘Lothar’ in December 1999), forest management (Art. 3.4) results in a net carbon sink in living and dead biomass. This forest sink is nonetheless limited, as the rotation periods (using trees at a later stage) cannot be extended at will if the forest is to be managed sustainably. Carbon stocks in durable wood products under Article 3.4 have also been classified as a carbon sink since 1990, but they have tended to shrink in recent years.
For accounting under the Kyoto Protocol, this carbon balance from forest management and wood products is compared with a reference value at the end of the commitment period. Current estimates suggest that the sequestration performance credited will be in the range of a few hundred thousand tonnes of CO2-equivalents.
If more wood is harvested in the coming years, as foreseen by the Swiss Forest Policy, this would generally lower the forest’s carbon sink capacity in the future. However, a well-conceived cascade strategy for lumber use could absorb this effect and enable stored carbon to continue to protect the climate. Since large storm events and pest infestations have a decisive impact on the quantity of the carbon stored, the trend is difficult to evaluate.
- Related indicators
- Carbon balance of land use
Comparability with the other Parties to the Kyoto Protocol pertains.
The greenhouse gas emissions and the carbon balance of forest management are published in the national Greenhouse Gas Inventory in accordance with the Kyoto Protocol. The methods used are consistent with IPCC (Intergovernmental Panel on Climate Change) guidelines.
To establish changes in carbon stocks – expressed as CO2-equivalents – the levels of carbon released by deforestation, and those absorbed by afforestation, are taken into account in addition to the carbon balance of forest management, including harvested wood products. For the Kyoto Protocol calculation at the end of the commitment period, forest management is compared with a reference value, the Forest Management Reference Level. The value may change until the final calculation is done. Carbon dioxide (CO2) is by far the largest contributor to greenhouse gas emissions, while methane (CH4) and nitrous oxide (N2O) from forest fires and drained wetlands contribute to a lesser extent.