Silence of the Clams

What's the price tag for lighting Las Vegas and irrigating Southern California during the past 70 years?

• Mark Cheater
• Apr 01, 2001

What's the price tag for lighting Las Vegas and irrigating Southern California during the past 70 years? Several billion clams, according to a team of scientists that recently studied the ecological impacts of dams and diversions along the Colorado River.

When the mighty river flowed freely, an estimated six billion clams thrived in the Colorado River Delta, where sediments from the Rocky Mountains washed into the Gulf of California. But seven decades of dams and water diversions along the river have reduced the flow to a trickle, and cut shellfish in the delta from an average of 5 per square foot to about 0.3 per square foot today, according to the researchers.

"These estimates indicate a nearly 20-fold drop in the shellfish productivity in the delta since the river has been diverted by humans," says Michal Kowalewski, a geologist at Virginia Polytechnic Institute.

Why should we care about a bunch of lost clams? For at least two reasons, says Kowalewski: "One, they tell us something about the destruction of that ecosystem. And two, they are important sources of nutrients to other organisms, such as migratory birds."