▁have ▁become ▁val ued ▁for ▁their ▁highly ▁product ive ▁so ils ▁and ▁are ▁included ▁in ▁the ▁Corn ▁B elt . ▁As ▁an ▁example ▁of ▁this ▁land ▁use ▁intensity , ▁Illinois ▁and ▁Iowa ▁rank ▁ 4 9 th ▁and ▁ 5 0 th , ▁out ▁of ▁ 5 0 ▁US ▁states , ▁in ▁total ▁un c ult iv ated ▁land ▁remaining . ▁ ▁D rier ▁short gr ass ▁pra i ries ▁were ▁once ▁used ▁mostly ▁for ▁open - range ▁ran ch ing . ▁But ▁the ▁development ▁of ▁the ▁bar bed ▁wire ▁in ▁the ▁ 1 8 7 0 s , ▁and ▁improved ▁ir rig ation ▁techniques , ▁means ▁that ▁this ▁region ▁has ▁mostly ▁been ▁converted ▁to ▁cro pl and ▁and ▁small ▁f enced ▁past ure ▁as ▁well . ▁ ▁Bio fu els ▁▁ ▁Research , ▁by ▁David ▁T il man , ▁e colog ist ▁at ▁the ▁University ▁of ▁Minnesota , ▁suggests ▁that , ▁" B io fu els ▁made ▁from ▁high - d iversity ▁mi xt ures ▁of ▁pra irie ▁plants ▁can ▁reduce ▁global ▁war ming ▁by ▁removing ▁carbon ▁dio x ide ▁from ▁the ▁atmosphere . ▁Even ▁when ▁grown ▁on ▁infer t ile ▁so ils , ▁they ▁can ▁provide ▁a ▁substantial ▁portion ▁of ▁global ▁energy ▁needs , ▁and ▁leave ▁fert ile ▁land ▁for ▁food ▁production ." ▁Un like ▁corn ▁and ▁so y beans , ▁which ▁are ▁both ▁directly ▁and ▁indirect ly ▁major ▁food ▁cro ps , ▁including ▁liv est ock ▁feed , ▁pra irie ▁grass es ▁are ▁not ▁used ▁for ▁human ▁consumption . ▁Pra