Fuzzy logic modeling is a useful method for evaluating landscapes for conservation and resource planning and has been successfully used in different types of ecological and environmental studies. A variety of software packages have been produced to facilitate fuzzy logic modeling, but each is either associated with a specific computer program or does not comprise a complete modeling system. The Environmental Evaluation Modeling System (EEMS) is a platform-independent fuzzy logic modeling framework for environmental decision support. EEMS has been designed so that it can easily be adapted to work with different file types and interface with other software systems. It has been implemented to work with NetCDF and CSV file formats as a command line application, in the ArcGIS ModelBuilder environment, and as part of a web-based data exploration tool. In a performance test, EEMS was run using a dataset with four million reporting units per map layer and yielded execution times of less than 30 s.Results from an EEMS model for Utah and the Colorado Plateau show a complex pattern of site sensitivity.