Why don trees grow on the Great Plains?
Persons of the urban smarty-pants persuasion are now thinking: Duh. Everybody knows that if you have a little rain, you can grow little plants; if you have a lot of rain, you can grow big plants. The Great Plains are dry, so of course all that grows there is grass. Except it’s not that simple, you knuckleheads. True, the plains themselves–anything west of Omaha, say–are too arid to support trees. But that doesn’t explain the “prairie peninsula.” By this we mean the immense wedge of grassland that extends eastward from the Great Plains through Iowa and Illinois, over parts of Minnesota, Missouri, and Wisconsin, and into western Indiana, with isolated patches in Michigan and Ohio. In terms of average annual rainfall, this area, or at least the eastern end of it, doesn’t differ significantly from the regions to the immediate north, south, and east, which prior to European settlement were dense woods. Trees can and do grow in the peninsula–the Illinois prairie, for example, was original
