Phantom forest at Tahoe reveals past climate change

John Kleppe, PhD

JOHN KLEPPE holds an 800-year-old slab of yellow pine brought up from Fallen Leaf Lake. Photo courtesy Mountain Counties Water Resources Association

On March 15, Mountain Counties Water Resources Association, in conjunction with the Association of California Water Agencies Region 3, met at the Ridge Golf Course and Event Center in Auburn to hear the latest on climate change.

John Kleppe, whose home is on the shores of Fallen Leaf Lake, brought evidence of a 300-year-drought in the Lake Tahoe area. If it happens again, will we be ready? he asked.

John Kleppe is professor emeritus at University of Nevada, Reno, where he was chairman of the Electrical Engineering Department.

Dr. Kleppe often takes his boat out to fish on Fallen Leaf Lake. Fallen Leaf Lake is one mile south of Lake Tahoe and 500 feet higher. It is a small lake, almost three miles long and a mile wide. The average depth is 240 feet. The deepest part is 492 feet.

For many years, Kleppe’s line kept bumping into something and he was puzzled why. What he caught was not a rare species of fish, but something even more rare — a tree from a forest dating back to medieval times.

Although the clarity of the lake is high, he could not see anything underwater. As a scientist, this was a mystery he had to solve. He tried SONAR, but got no soundings. In the late 1990s, he hired a diver, who quickly surfaced with a branch in hand. Kleppe sent a sample to Lawrence Livermore National Laboratory for carbon dating.

The tree, a yellow pine, dated back to around 1215 A.D. It had mineralized, and was as perfectly preserved as a marble statue. It was waterlogged, so it absorbs SONAR.

Further investigation revealed a number of trees nearly 100 feet tall and 15 feet in diameter, indicating they were over 200 years old when they died. This signifies that a “mega drought” occurred during the medieval period around 850 to 1150 A.D. The dry period was followed by an extremely wet period. There are signs that another lengthy drought occurred later.

Three older trees were discovered, suggesting that severe droughts happened farther back in time.

These longer cycles are different that the shorter fluctuations that have been recorded in the last 150 years.

Graham Kent, University of Reno Seismology Lab director, used a remotely operated underwater vehicle to create high-definition fault mapping of the bottom of Fallen Leaf Lake. His team traced the west Tahoe fault line. It is a 7.3 capable normal fault. Kleppe said Kent believes it may be ripe for action.

Kleppe said there is “a disconnect between science and society. We need to separate funny science from real science. We need to start saving water.”

For more information, including a report on the entire meeting, visit

Mountain Counties Water Resources Association

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