 The World Wide Fund For Nature divides the Missouri River watershed into three freshwater <unk> : the Upper Missouri , Lower Missouri and Central Prairie . The Upper Missouri , roughly encompassing the area within Montana , Wyoming , southern Alberta and Saskatchewan , and North Dakota , comprises mainly <unk> shrub @-@ steppe grasslands with sparse biodiversity because of Ice Age <unk> . There are no known endemic species within the region . Except for the headwaters in the Rockies , there is little precipitation in this part of the watershed . The Middle Missouri ecoregion , extending through Colorado , southwestern Minnesota , northern Kansas , Nebraska , and parts of Wyoming and Iowa , has greater rainfall and is characterized by temperate forests and grasslands . Plant life is more diverse in the Middle Missouri , which is also home to about twice as many animal species . Finally , the Central Prairie ecoregion is situated on the lower part of the Missouri , encompassing all or parts of Missouri , Kansas , Oklahoma and Arkansas . Despite large seasonal temperature fluctuations , this region has the greatest diversity of plants and animals of the three . Thirteen species of <unk> are endemic to the lower Missouri . 
