The 100th meridian has been a traditional dividing line in the United States, notes the Earth Institute at Columbia University. Historically, the line has separated the arid, sparsely populated, wheat-growing Great Plains from the humid, fertile, corn-growing Midwest. Recently published research indicates that the dividing line may be moving eastward as the climate warms, with implications for agriculture. A combination of rising temperatures and changing weather patterns have pushed the humid-arid divide some 140 miles east since 1980, researchers say. They warn that the continuation of this trend will lead to significant crop and land-use changes in this region, which has historically been fertile crop ground.