How much of the United States is developed? Twenty-five percent? Fifty? Seventy-five? How about 5.4 percent? That's the Census Bureau's figure. And even much of that is not exactly crowded: The bureau says that an area is "developed" when it has 30 or more people per square mile.

But most people do live in developed areas, so it's easy to get the impression that humans have trampled nature. One need only take a cross-country flight and look down, however, to realize that our nation is mostly open space. And there are signs that Mother Nature is gaining ground. After furious tree chopping during America's early years, forests have made a comeback. The U.S. Forest Service notes the "total area of forests has been fairly stable since about 1920." Agricultural innovations have a lot to do with this. Farmers can raise more on less land.

Yes, American houses are getting bigger. From 1970 to 2000, the average size ballooned from 1,500 square feet to 2,260. But this hardly means we're gobbling up ever more land. U.S. homeowners are using land more efficiently. Between 1970 and 2000, the average lot size shrank from 14,000 square feet to 10,000.

In truth, housing in this country takes up less space than most people realize. If the nation were divided into four-person households and each household had an acre, everyone would fit in an area half the size of Texas. The United States is not coming anywhere close to becoming an "Asphalt Nation," to use the title of a book by Jane Holtz Kay.