In our departmental seminar on Friday, we had a speaker with a background in forestry. He showed some graphs related to the amount of forest land in the United States, and I have to say I was a bit surprised how much land is in forest.
Of all the land in the U.S., only 14.8% is in cropland used for crops (it's 17.7% in the contiguous 48 states). 27.1% is in grassland or pasture (32.3% in the 48 contiguous states). About a quarter of the land (both in the US as a whole and in the lower 48) is in forest that is not grazed, and another 5.6 to 6.7% is in grazed forest land. By the way: Special uses includes: "rural transportation, national/ State parks, wilderness and wildlife areas, national defense and industrial areas, and farmsteads and farm roads" and miscellaneous land includes "marshes, open swamps, bare rock areas, desert, and tundra."
Also from the 2007 report:
These are useful statistics in light of the common sorts of things I read like "agriculture has more impact on the environment than any other human activity" or "agriculture is the biggest threat to the environment."