Invertebrates, or animals without backbones, make up 97% of all animal species. The Crown of the Continent supports high invertebrate diversity due to several factors. Major river drainages provide channels for species migration to the region. Complex landscape topologies, encompassing prairies to mountains, offer a variety of life zones necessary to sustain the rich biodiversity of host plants needed to support many invertebrate insects. Wildland fires also play a role, as invertebrates specializing in burned areas thrive in the habitat mosaics which result from fires.