LIANE HANSEN, host:
While oil continues to cloud the waters of the Gulf Coast, across the country in California, scientists are studying a different problem: The San Francisco Bay is becoming clearer.
And as Lauren Sommer reports, this poses a threat to the area's fragile wetlands.
Unidentified Man: Ladies and gentlemen, welcome to Alcatraz. Thank you for...
LAUREN SOMMER: Hundreds of tourists are pouring off the ferry on Alcatraz Island today. But two of the passengers aren't here for the historic prison. What they're looking for is underneath the dock.
David Schoellhamer is a hydrologist with the U.S. Geological Survey. He holds up a bottle of cloudy bay water that he just collected.
Professor DAVID SCHOELLHAMER (Hydrologist, U.S. Geological Survey): What we're measuring here is suspended sediment. You can think of it as the little microscopic rocks that are floating in the water.
SOMMERS: To most of us that would jut be mud. But for Schoellhamer, the bottle holds important clues about the bay's history. About 10 years ago, he noticed something strange in these samples: The bay's water was becoming clearer, after more than a century of murkiness.
Prof. SCHOELLHAMER: Back in the 1800s, late-1800s during the Gold Rush, the gold miners used essentially fire hoses and water cannons to literally wash down mountainsides to extract the gold from the sediment.
SOMMERS: The mining sent massive pulses of earth from the Sierra foothills into the watershed.
Prof. SCHOELLHAMER: About 250 million cubic meters of sediment deposited in the bay.
SOMMERS: That's enough mud, rock and sand to fill 36 million dump trucks.
Prof. SCHOELLHAMER: It really threw everything out of whack because there was so much extra sediment.
SOMMERS: Schoellhamer says now that the extra sediment has finally worked its way out the Golden Gate, the bay's water is about 30 percent clearer than it was 10 years ago. That could help some fish and other species. But for the bay's shoreline, clearer doesnt always mean better.
Professor JOHN CALLAWAY (Environmental Science, University of San Francisco): So we're at the China Camp State Park, right on the edge of San Pablo Bay, and we're on the upper part of a salt marsh.
SOMMERS: On the waters' edge in San Rafael, Professor John Callaway of the University of San Francisco and his researcher Evyan Borgnis are taking a core sample of this soggy wetlands, by pulling up a thick aluminum tube that they've sunk into the mud.
Prof. CALLAWAY: So we just slowly push. It's stuck.
SOMMERS: This thick mud was once sediment out in the bay. Callaway says it's key for a wetland's survival. With every high tide, these marshes are built up by the sediment they trap from the water. And less sediment in the bay could spell trouble. Thats because these wetlands are facing a new pressure: rising sea levels, which scientists are predicting will inundate these tidal marshes over the next century.
Prof. CALLAWAY: The big question is, how much will it go up in the future? If it goes up to eight to 10 millimeters per year, then I think many wetlands are really unlikely to survive.
SOMMERS: Wetlands are home to all sorts of plants and animals, from egrets to harbor seals and fish. But they also do another job: protect shoreline development from storm surges.
Steve Goldbeck is with the Bay Conservation and Development Commission. He says critical infrastructure, like Oakland and San Francisco Airports are right in the path of rising waters.
Mr. STEVE GOLDBECK (Deputy Director for Climate Change and Legislation, Bay Conservation and Development Commission): What wetlands do is they can absorb those peak storm surges, those waves that are rolling in. When they hit the wetland, it knocks down the wave peaks.
SOMMERS: With 80 percent of the bay's historic wetlands already destroyed, Goldbeck says restoration projects will be a vital tool to combat sea level rise. Right now, millions of cubic yards of sediment are dredged in the bay to keep shipping channels clear. Goldbeck's agency is looking at how to recycle that material, now that sediment is becoming a valuable resource.
For NPR News, Im Lauren Sommer.
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