Within Gap Analysis, two sets of information are needed to model animal distributions. These are the digital vegetation map and the wildlife habitat association data linking particular species to mapped vegetation classes. This simple linkage provides a description of the predicted spatial location for each animal species in the database. Once identified, the maps go through an additional screening to further refine the predicted distribution. This involves comparing the predicted distribution to more refined spatial data.
Predicted distributions fail for several reasons.
Second, species associated with hydrologic regimes are grossly overestimated, unless hydrology is incorporated as a linear string. Fossorial rodents, such as pocket gophers and ground squirrels, are also overestimated, presumably because Gap Analysis vegetation maps do not integrate soil characteristics very well. Last, rare species having localized distributions are also overestimated. Nonetheless, species range predictions from Gap Analysis exceed the resolution of existing range maps. Discussion Gap Analysis is a method of identifying gaps in the protection of biodiversity at state, regional, and national scales.