ToSIA is a decision support tool that was originally developed for the forestry sector, which analyses sustainability impacts of Forest-Wood-Chains (FWCs) and value chains related to resource use. Value chains are chains of production processes that are linked with products. ToSIA compares alternative process chains by using scenarios to analyse the sustainability effects of changes due to deliberate actions (e.g. in policies or business activities) or due to external forces (e.g. climate change, global markets). Impacts are assessed by calculating changes in material flows and indicators of environmental, economic and social sustainability within each forest value chain.