ST-Sim version 2.0 is now available for download at https://apexrms.com/projects/stsm. In addition to the continued support for developing spatially-explicit state-and-transition simulation models (STSMs), this version also includes the ability to track, for each simulation cell, pools of stocks (e.g. carbon) and flows between pools (e.g. carbon fluxes). The stocks and flows are completely customizable: users can define any number of stocks and flows; furthermore flow pathways can occur automatically each timestep (e.g. biomass growth of carbon in forests), or they can be triggered by a transition in the STSM (e.g. carbon emissions due to fire). The ST-Sim stock-flow module has been designed to allow for the rapid development of IPCC-compliant Tier 2/3 greenhouse gas inventories associated with Agriculture, Forestry and Other Land Use (AFOLU).