Sprawl isn't just eating up the countryside—it's also blocking the breezes that would otherwise clear out air pollution. That's according to a new study of Houston from the National Center for Atmospheric Research, to be published in the Journal of Geophysical Research.

Sprawl is first and foremost about pavement leading to all those subdivisions, strip malls and suburbs. That pavement soaks up heat during the day and releases it at night, warming the otherwise cooler nighttime air. It's known as the urban heat island effect.

In Houston, this causes a smaller than usual difference between the temperatures of the land and the sea at night. And that means weaker sea breezes to clear away the smog.

Houston is already fighting an uphill battle against the atmospheric residue of refineries, petrochemical facilities and mile after mile of cars stuck in traffic. What's worse, all those buildings break up whatever breezes there are, further reducing the chances of clearing the air.

The study authors write that “the very existence of the Houston area favors stagnation." Time to pound the pavement—and exchange some for more greenery.  

—David Biello

[The above text is an exact transcript of this podcast.]