Figure 16: Fractional Impervious Surface Area. The U.S.-constructed impervious surface area (ISA) in 2000 was nearly the size of Ohio. Population is increasing at a rate of 3 million people per year. Annual U.S. public and private sector construction spending is greater than US$480 billion. This includes more than a million new single-family homes and more than 10,000 miles of new roads per year. Credit: C.D. Elvidge, NOAA/National Geophysical Data Center.

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