California’s sinking delta

Dennis Baldocchi often drives past the ruins of his grandmother’s house on Sherman Island, in northern California’s Sacramento-San Joaquin River Delta. Flooding gutted the house when the island’s levee broke 40 years ago. Today, grass grows through the floors and chickens wander through.

To Dr. Baldocchi, the slanting hulk whispers an unsettling truth: The land that his family farmed for three generations is sinking farther below sea level each year.

Immigrants began arriving at the Sacramento River Delta 150 years ago. They drained 450,000 acres of marshy lands so that they could farm asparagus, corn, and sugar beets.

Their ingenuity fueled an economic boom, but it also triggered a slow-motion catastrophe: Draining allowed oxygen to penetrate the soil, permitting microbes to consume organic detritus that had lain undisturbed for millenniums, and to churn out carbon dioxide. As the soil deflated, the land sank as much as two inches per year.

Baldocchi, now a biogeochemist at the University of California in nearby Berkeley, spent much of his childhood on Sherman Island, pheasant hunting and helping harvest asparagus on his uncles’ farms. He didn’t appreciate the slow changes that were taking place in the land until he returned in 1999, after 22 years away.

Baldocchi motions to the road ahead. It hovers six feet above the plowed fields. The roads have sunk more slowly than surrounding fields, since blacktop slows the seepage of oxygen, which microbes need to devour peat. “When you grow up here, an inch or two per year you don’t notice,” he says. “But if you’re gone 22 years and it drops two or three feet, you get a visual sense of it.”

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