The Native Prairie Vegetation Inventory (NPVI) Polygons is a quarter section-based vegetation inventory that covers the southern part of Alberta. The native prairie is defined in the Native Prairie Conservation Action Plan as an area of unbroken grassland or parkland dominated by non-introduced species, and an area of previously broken grassland that has reverted back to natural vegetation (30 to 60 years). The Native Prairie Vegetation Inventory extends beyond the Grasslands Natural Region to include data for adjacent areas, such as the Cypress Hills. In addition to the Grassland Natural Region, the Native Prairie Vegetation Inventory (NPVI) Polygons include areas that belong to the Foothills Parkland, Central Parkland, Montane, Dry Mixedwood Boreal and Lower Foothills Natural Subregions.