Plankton for Obama

Robert Krulwich has a crazy ability in weaving together science, history and politics.  In his latest blog post, he identifies a streak of democratic counties in the south as the same counties that had most nutrient rich soils, due to plankton deposits.  Because these areas were lucrative for farming, more slaves were concentrated here. While many black Americans moved north after the civil war, some inevitably stayed behind, and generations later, it is their descendants who are painting the South blue. 

From Krulwich Wonders:

Map of contiguous U.S., showing percentage of population self-reported as "black," by census tract, 2000.

In this 2000 census, you can see that the counties with the biggest populations of African-Americans still trace that Cretaceous shoreline.

This, says marine biologist McClain, explains that odd stretch of Obama blue; it’s African-Americans sitting on old soil from ancient organisms that turned sunshine into fertilizer. So plankton remain a force in Southern elections — though not always, not continuously. After the Civil War, when the South voted solidly Democratic and Jim Crow laws ruled, many blacks couldn’t vote, so the pattern disappears. Voting rights laws hadn’t been passed during the Goldwater-Johnson election of 1964, so in this map, the African-American difference is invisible.

Photo from