2. how have humans altered the landscape of the united states?

Human beings are one of the most active geographic movers. their activities such as irrigation, farming and pollution greatly alters the landscape of a place. For example farming and livestock keeping has greatly led to soil erosion, and increased desertification in such areas due to cutting of trees and vegetation. pollution has lead to global warming which in effect has been leading to a rise in the sea level. For example,Miami has been making attempts to mitigate the effects of global warming and associated sea level rise.

Democracy and darwinism would be my answer.