We’ve all heard stats about coastal populations increasing over time. As someone who reviews land cover imagery, I’m able to see how this plays out on the landscape. More people usually means more houses, roads, and shopping centers to accommodate the increasing numbers that either move to the coast or are born there. How are these two things related (i.e. does a certain amount of population growth have a corresponding amount of development increase)? Coastal land, however you define coastal, is not infinite. While coastal populations may continue to increase, the land is not. Given issues of erosion, sea level rise, and subsidence, in some places the total land area is actually shrinking.

This got me wondering how has population changed from 2000 to 2010 and how does this compare to changes in developed land in my county? This was pretty easy. I got population statistics from the US Census Bureau and Census Viewer for Charleston County, SC. Then using the Coastal Change Analysis Program (C-CAP) Land Cover Atlas, I took a look at the total amount of new development from 2001 to 2010. The population went up by 13%, and there was an 8.4% increase in development (almost 13% increase in impervious surface) during that time period. A lot of the new development occurred along the edges of suburban areas, replacing woody wetland and forested areas with new subdivisions (Figure 1). Then I wondered, how does this compare to another county such as Cuyahoga, OH? This county actually had a decrease in population of -8% from 2000 to 2010 (people migrating to Charleston perhaps?), yet development increased by 3% and impervious surface increased 4.4%. The new development is scattered throughout the county, distributed more evenly than Charleston’s new developed land, which was mostly concentrated around suburban areas (Figure 2).  Forest and woody wetlands were the biggest losers to developed land in Cuyahoga County too.

Figure 1. Changes in developed land in Charleston County, SC (outlined in yellow) from 2001 - 2010. Green = gains, red = losses.
Figure 1. Changes in developed land in Charleston County, SC (outlined in yellow) from 2001 – 2010. Green = gains, red = losses
Figure 2. Changes in developed land in Cuyahoga County, OH (outlined in yellow) from 2001 – 2010. Green = gains, red = losses

What was the national trend along the coast?

You guessed it…more development. In 2006, the coastal area mapped by C-CAP (Figure 3) contained 41% of the CONUS developed lands even though it makes up only 25% of the total area. From 1996 to 2010, there was a 5,726 sq mile increase in development – roughly the size of Connecticut. This is equivalent to 542 football fields of new development per day, which potentially means more stuff in harm’s way, making coastal areas more vulnerable to storm events and sea level rise. More precaution is necessary is keep ourselves, buildings, drinking water, oysters (the list goes on) safe.

Figure 3. C-CAP mapping boundaries highlighted in green.

There are some positives that go along with increased development…bear with me here. More people along the coast can boost the local economy, potentially leading to more resources to protect existing natural habitat, greater appreciation of healthy ecosystems, and a resolve to apply smart growth concepts during the planning process. In some places local restoration activities have actually helped communities see gains in wetlands areas – not enough to make up for all the losses, but it is good news that more and more people are concerned with restoring areas to their natural state.