InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs)
InVEST, a.k.a. Integrated Valuation of Ecosystem Services and Tradeoffs, is a suite of models and software tools under development by the Natural Capital Project. It currently runs in ArcGIS version 9.3 (service packs 1 or 2) with the Spatial Analyst extension installed and activated. In addition, you should have Python 2.5 or higher, which is typically installed automatically as part of ArcGIS. InVEST aims to provide a consistent methodology for measuring and comparing the value of multiple ecosystem services across real landscapes. For more information, visit the Natural Capital Project website.