COINS: an integrative modelling shell for carbon accounting and general ecological analysis

It is common for a range of models to be developed to investigate broadly similar ecological and environmental phenomena. This inevitably results in collections of models that, although individually possessing unique characteristics, also share a number of key similarities. Here we describe a new modelling shell called COINS (COmparison and INtegration Shell) within which many related models can be co-located, and where model similarities are exploited to facilitate rapid model development and analysis. The philosophy underlying COINS is to separate computer code that is shared across different models, such as common process descriptions, or shared data input and output routines, from the core equations of each model. This reduces code redundancy, allowing the modeller to more directly focus on the process of model formulation. As an integrative tool, COINS can be used to (i) construct component models, (ii) integrate existing components to develop a simulation, and (iii) allow end users to run a simulation for analysis and scenario comparison. The COINS software has been developed with a specific focus on modelling the terrestrial carbon cycle, but its utility is potentially broader, particularly within the general area of ecological analysis and natural resource management. Three examples based on terrestrial carbon accounting at a range of spatial scales (point, landscape, continental and global) are used to illustrate major COINS features, including flexibility in the spatial deployment of models, the ability to combine different models within the same simulation, and Monte Carlo sensitivity analyses.