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present discussion the primary concern is with the biophysical 

 environment of the estuarine zone, and the regions describing this 

 environment are the basic unit for analysis. Where necessary 

 political subdivisions have been broken at county boundaries as 

 required to present a consistent analysis. 



The coastal counties contain only 15 percent of the land area of 

 the United States, but within this area is concentrated 33 percent 

 of the Nation's population, with about four-fifths of it living in 

 primarily urban areas which form about ten percent of the total 

 estuarine zone area. Another 13 percent of the estuarine land area 

 is farmland, but this accounts for only four percent of the total 

 agricultural land of the Nation. The estuarine zone, then, is nearly 

 twice as densely populated as the rest of the country, and supports 

 only one-fourth as much agriculture per unit area. 



The magnitude of population and agricultural development in the 

 estuarine zone is shown in Table IV. 3.1 by densities in terms of 

 tidal shoreline. The few estuarine areas in the Pacific Southwest 

 show the greatest shoreline development for both living and farming 

 as shown by the population density of 3,980 persons per mile of tidal 

 shoreline and a farmland density of 4.9 acres per mile. The Middle 

 Atlantic region, in contrast, has a very high population density and 

 a low farmland density, showing how in this region the estuarine 

 zone developed as a center of population while agriculture developed 

 elsewhere. 



