Inside an underwater forest frozen in time

March 28, 2011 7:11:50 PM PDT
Scientists in the High Sierra have discovered a previously unknown forest, and there's a twist. The ancient trees in this forest are under water. They are standing at the bottom of Fallen Leaf Lake, just south of Lake Tahoe. New research shows both the forest and the lake hold critical clues to climate change.

Fallen Leaf Lake is already known for its spectacular beauty. Now it turns out the lake also has a dramatic secret.

"What I like to call a ghost forest," says Prof. Graham Kent of the University of Nevada, describing trees up to 100 feet tall, as high as a 10-story building, but covered by water. "We have old wood from a thousand years ago, 2,000, 3,000 down there."

Scientists in a small submarine took photos showing just a few of the hundred or more trees on the bottom of the lake. They're using state of the art sonar to map the mysterious forest and try to figure out why it's there.

"Side scan sonar technology is exactly the equipment that's used to find sunken ships," says Kent.

A high-tech image shows the lake has seen big changes in the water level over many years. A sonar device shows slices of the ground under the lake bottom.

Researchers say all this evidence confirms that a thousand years ago there was a prolonged drought in the Sierra. It lasted about 200 years -- long enough for huge trees to grow where Fallen Leaf Lake now sits. The precipitation is believed to have been just 60 percent of normal. That is similar to the devastating midwest "Dust Bowl" in the 1930s. Scientists believe it may happen again.

"So take the great Dust Bowl and extend it from 10 years to 200 and some years," explains Kent. "And just wonder how the economies of California and Nevada are going to be affected by it."

Kent says the long Sierra drought happened naturally a thousand years ago. But he and other top researchers believe human-caused global warming might bring on another severe drought even faster in the future. If that happens, Fallen Leaf Lake could be the proverbial canary in the coal mine.

"This is the lake that's going to start feeling the effects of the next drought, whenever that happens, much more than any other lake in the area," he says.

The research indicates the lake level might drop fast, as much as 50 to 100 feet in just a couple of decades, and that could bring huge change for thousands of vacationers who flock to the lake every summer.

Scientists plan more research to make more accurate predictions. But now at least they know Fallen Leaf Lake and its ghostly forest is the place to find answers.

"You don't get many chances to get a perfect record," says Kent.

The forest at the bottom of the lake was actually discovered by another professor who happened to be fishing on the lake. His lure got stuck in the top one of those 100-foot tall trees.

Written and produced by Jennifer Olney.


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