The Northern Rocky Mountain Biodiversity Challenge (NRMBC) is a free, tri-annual, crowd-sourced, 4 day collaboration known as a bioblitz. It is modelled after the largest bioblitz, the once yearly springtime international City Nature Challenge (CNC). It's an ecoregional competition, comprised of 106 individual projects in jurisdictions that intersect in whole, or in part, with the Yellowstone to Yukon ecoregion.