The philosophy behind the Habitat Evaluation Procedures (HEP) is that an area can have various habitats, and that these habitats can have different suitabilities for species that may occur in that area. Further, we assume that the suitabilities can be quantified (via Habitat Suitability Indices [HSIs]) and that the different habitats have measurable areal extents. The overall suitability of an area for a species we postulate can be represented as a product of the areal extents of each habitat and the suitability of those habitats for the species.
If this is true, we may further postulate that as habitat changes through time, either by natural or human-induced processes, we can quantify the overall suitability through time by integrating the areal extent-suitability product function over time. Thus, we can quantitatively compare two or more alternative management practices of an area with regards to those practices affecting species in that area. For example, we can judge the effects of logging, mining, and cattle grazing, versus no use. Furthermore, HEP allows us to quantify the effects of mitigation (not so great a negative impact) or compensation (improve another like area to make up for lost habitat in the impacted area).
This is an important tool for land use managers, as they can quantify the effects of alternative management plans over time, and provide for mitigation and compensation that can allow fair use of the land and maintain healthy habitats for affected species.
The HEP accounting program uses the area of available habitat and Habitat Suitability Index (HSI) to compute the values needed for Habitat Evaluation Procedures (HEP) as described in the Ecological Services Manual (ESM 102) and the HEP training course Habitat Evaluation Procedures. The compiled program requires two floppy disk drives or a hard disk, and 64 kilobytes of RAM.