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Mapping and modeling SPECIES ranges and distributions

Published May 27, 2011

Knowing where species occur is vital to biodiversity protection, climate change research, and conservation planning. Because we are unable to know all the places in which a species occurs, we use computer models that can help us predict where a species occurs based on what we know about its habitat preferences.

To create a predicted distribution model for a species, we first define that species’ range, which is the general area within which that species can be found.  Currently, GAP is creating national species range maps and distribution models for most of the mammals, birds, reptiles, and amphibians that occur within the U.S.

Distribution of Lark Bunting in the United States

Protected Status of Lark Bunting in the United States

Each species range map is based on 12-digit HUCs (i.e., hydrologic units).  Each HUC within a species’ range is attributed with seasonal range information such as breeding, winter, or migratory.  A separate species distribution model is created for each species for each season because animals use different habitat during each season.  Each species range map is reviewed by expert biologists to ensure the accuracy of the data.

Species distribution models depend on known species habitat relationships or species observation records.  A wildlife habitat relationship database (WHRDB) is used to store and maintain the extensive information on species habitat relationships acquired from the published literature.  In addition, spatial data are compiled that describe the relationship between a species’ habitat and other elements such as land cover and elevation.  For each species, these spatial data are used as model inputs based on the habitat preferences stored in the WHRDB.

A predicted distribution map for each species is created based on the model inputs, which are based on the WHRDB and spatial data.  This map is reviewed by expert biologists and revisions are made based on their comments.  Each species’ predicted distribution is based on the best available data and is a binary representation of where a species is likely to occur.

Species modeling outputs include:

  • 12-digit HUC range maps showing seasonal use for each species;
  • Spatial data as model inputs that include the entire US;
  • WHRDB that include species common name, scientific names, habitat relationships, life history characteristics, etc.;
  • Species observation records;
  • Binary (presence/absence) representation of species distribution across US.

See our Species viewerto explore Land Cover data online>>