As part of the United Nations Framework Convention on Climate Change (UNFCCC), Switzerland is obliged to report the CO2 balance of its forests and the surrounding countryside. WSL's Resource Analysis Group provides the Federal Office for the Environment (FOEN) with forest carbon balances. They also perform updates and, if necessary, make improvements (on the basis of expert reviews) on new data and guidelines. The carbon stock in forests, increase in biomass and utilization and mortality are calculated using the latest National Forest Inventory (NFI) data. Carbon in the forest soil, and its changes, are estimated using the model Yasso07.
From 2015, CO2-budgets of land use, land-use change and forestry for the GHGI have to be calculated with the so called "Forest Management Reference Level (FMRL)”. The FMRL is a simulation of forest development under a predefined harvesting level. The actual sink is then defined as the difference between the simulated level of forest development and the forest development calculated by most recent NFI data.