Hot Spots of Growth: Increasing Population in a Finite Space

More than 160 million people live in the coastal watershed counties of the United States and the five U.S. territories, representing just over half the U.S population in 2010. Since 1970, the coastal population has grown at the same pace as the rest of the nation; however, this growth has occurred in less than 20 percent of the U.S. land area (excluding Alaska).

This has implications for coastal population density, which in 2010 was 319 persons per square mile, compared to 61 persons per square mile in inland areas. To illustrate, between 1970 and 2010, coastal watershed counties added 50.8 million people, a 45 percent increase, but this increase added 99 new residents per square mile, compared to 23 new residents per square mile in inland areas (Figure 1).

Coastal population density is expected to continue to increase, which is a challenge for planning and managing these ecologically sensitive and economically important areas.

population density

Figure 1. Population density in coastal watershed counties, inland counties, and the U.S. as a whole from 1970 to 2020.

(U.S. Census Bureau, 2011; Woods and Poole Economics, Inc., 2011)

San Gabriel Valley (Los Angeles County, CA)

San Gabriel Valley (Los Angeles County, CA) is located within the greater Los Angeles metropolitan area and is almost entirely developed in suburban form.
Credit: Deborah Nieters