Is Oklahoma among the most biologically diverse states by number of ecoregions? 

Oklahoma has 12 Level III ecoregions defined by the EPA, or small regional ecosystems with distinct assemblages of biodiversity, which ties with Texas for No. 3 for states with the most ecoregions after Alaska and California.   

There are 846 terrestrial ecoregions, which are grouped into 14 broader biomes – extensive ecosystems occurring globally, and characterized by the structure and function of their species rather than the particular species themselves – making ecoregions better for representing biodiversity. 

Oklahoma’s ecoregions, which include High Plains, Cross Timbers, and Ozark Highlands, span the three biomes of temperate grasslands, savannahs and shrublands, temperate conifer forests, and temperate broadleaf forests and mixed forests. 

In addition to physical factors, Oklahoma owes its rich biodiversity to ecological factors, including its wide range of climates. 

According to The Nature Conservancy, Oklahoma ranks No. 16 for species diversity at 3,616 species and No. 9 for both bird and reptile diversity.