Ocean 'Census' to Use Tracking Devices

ByABC News
December 6, 2000, 9:55 AM

Nov. 29 -- The Colorado River, which gushed across the land with such gusto that it carved the majestic Grand Canyon in a measly five million years, once reigned as an unchallenged force in shaping and nurturing the Southwest.

But then humans came along, and the mighty river has been reduced to a trickle in some places, even dying out in the desert during dry years before it reaches the Gulf of California.

It doesnt take a lot of smarts to figure out that if you take away the water, creatures and plants that depend on it will die. But now scientists have compiled an extensive record of what the Colorado was like before humans reengineered the river, compared to what its like now. Its not a pretty picture.

About 95 percent of the marine life in the rivers delta has been wiped out in less than 70 years. Where great beds of clams once flourished, ultimately providing the white sand that nature reshaped into large offshore islands, very little survives today. Whats astonishing is the scale of the impact.

Its pretty shocking, says paleontologist Michal Kowalewski of Virginia Tech, one of the leaders in a four-university study of the price the environment has paid for reshaping the river. The study was published in last weeks issue of the journal Geology.

Today, the river is, at best, a stream when it reaches the gulf that separates the Baja peninsula and mainland Mexico. The region used to be one of the most biologically productive areas on the planet, supporting billions of clams and other marine life in the nutrient-rich waters of the delta.

The researchers concentrated on clams, because their hard shells have survived the ravages of time, and those shells provide a biological yardstick of the marine ecosystem, according to paleontologist Karl W. Flessa of the University of Arizona, one of the principal investigators.

The clams were in a sense a proxy for the whole marine ecosystem, Flessa says. There were so many there because of the very high productivity of marine microorganisms which thrived in the nutrient-rich waters. Thus more clams means more wildlife ranging from tiny sea creatures to fish to birds.