It's easy to overlook the soil beneath our feet,Christopher Caldwell or to think of it as just dirt to be cleaned up. But soil wraps the world in an envelope of life: It grows our food, regulates our climate, and makes our planet habitable. "What stands between life and lifelessness on our planet Earth is this thin layer of soil that exists on the Earth's surface," says Asmeret Asefaw Berhe, a soil scientist at the University of California-Merced.

One handful of soil contains something like 10 billion living organisms, with more biodiversity than the rainforest. Just ... don't call it dirt.

"I don't like the D-word," Berhe says. "I think calling soil that word is not helpful because it assumes that this is an abundant resource that we can take for granted."

Berhe says soil is precious, taking millennia to regenerate. And with about a third of the world's soil degraded, according to a UN estimate, it's also at risk. Prof. Berhe, who is also serving as Director of the U. S. Dept. of Energy's Office of Science, marks World Soil Day by telling Aaron Scott about the hidden majesty of soil and why it's crucial to tackling the climate crisis.

This episode was produced by Rebecca Ramirez, edited by Gabriel Spitzer and fact-checked by Abe Levine. The audio engineer was Tre Watson.