An underwater forest reveals the story of a historic megadrought

  • Ancient trees like this one preserved in the waters of Fallen Leaf Lake in California are helping scientists piece together the region's drought patterns.

    Graham Kent
  • Ancient trees like this one preserved in the waters of Fallen Leaf Lake in California are helping scientists piece together the region's drought patterns.

    Phil Caterino
 

A curved tree saw in his gloved hand, a scuba tank on his back, Phil Caterino worked quickly to slice through a pine branch 100 feet below the surface of a small tarn south of Lake Tahoe. Bubbles streamed from the regulator in his mouth, rising through the blue alpine water and green flecks of algae in Fallen Leaf Lake. That autumn day in 1997, Caterino briefly considered what would happen if he accidentally nicked the air hose running to his mouthpiece, or cut his orange dry suit, letting the 39-degree water rush in. "I'd be at the bottom of the lake, dead in about five minutes," he mused.

Having dived some 400 high-altitude lakes over the course of 30 years -- often reciting a protective Washoe prayer beforehand -- Caterino, director of the Lake Tahoe-based environmental nonprofit Alpengroup, doesn't shy away from occupational hazards. He surfaced a few minutes later, branch in hand. Even though the tree it came from had been stewing underwater for 800 years, it still smelled pungently of sap.

This botanic relic is one of several medieval trees, ranging from 68 to 100 feet tall, standing upright at the bottom of the lake. They grew during a 200-year megadrought in the Sierra Nevada between the 9th and 12th centuries, when precipitation in the area fell to less than 60 percent of the average between 1969 and 1992. Fallen Leaf Lake dropped about 150 to 200 feet below its current level, allowing the trees to grow above the lower shoreline. In the wetter years that followed, the lake quickly refilled, drowning the trees and sealing them in a liquid catacomb, safe from insects and fungi in the deep, low-oxygen water. There are also three older trees, which drowned between 18 and 35 centuries ago, standing upright on the lake floor, which suggests that severe droughts struck even further back in time.

The medieval trees' existence adds to the body of research documenting the Sierra Nevada's past megadroughts. Researchers have found stumps of long-dead trees in rivers, lakes and marshes in the region, indicating not one, but two medieval megadroughts -- the other lasting about 140 years in the 13th and 14th centuries, dwarfing the 20th century's Dust Bowl. Such megadroughts are a frightening prospect, and it's possible they could strike again.

John Kleppe, a professor emeritus at the University of Nevada-Reno who owns a lakeside home on Fallen Leaf, accidentally discovered the mysterious climatic archive. For 15 years, his fishing lures bumped against an unknown something in the deeps. "It looked like a fish strike," says Kleppe. "The pole just bent down. I never snagged and never caught anything." Curious, he finally asked Caterino to investigate.

Once Caterino found the first tree, Kleppe began combing the lake for more. He rigged a weighted 150-foot line between the undersides of two boats and slowly scoured the lake. Whenever he hooked a tree, he marked its location and later sent down a camera mounted on a propeller-driven Remotely Operated Underwater Vehicle, or ROV, with a pincer in the front for grabbing samples, and lights mounted on its side. Its footage showed the otherworldly trees with their roots supported by rocks and sediment buildup.

Graham Kent, director of the Nevada Seismological Laboratory, witnessed a surreal underwater scene first-hand from a two-person submersible in 2009. Peering out of the glass orb that encases pilot and passenger, Kent saw lures and fishing lines dangling like tinsel from tree branches, along with tiny single-celled organisms grouped into colonies resembling jellyfish, catching the subsurface light. "It was a bizarre Christmas-tree effect," he recalls. "I was just waiting for Rudolph the Red-Nosed Reindeer to come flying in."

The reindeer failed to appear, but Kent used torpedo-shaped sonar imaging equipment controlled from a boat to rule out the possibility that an earthquake had cracked the lake's bottom, causing water to leak out, or that a landslide had sent the trees tumbling into the lake. The sonar equipment not only helped confirm that drought caused the lake's waters to plummet, it also revealed the ancient shoreline from the past dry spell. His colleagues used tree-ring analysis and radiocarbon dating to calculate the trees' age. This, coupled with a model of how quickly water in the lake evaporates and leaks out into its neighbor, Lake Tahoe, gave the researchers a full picture of the drought's severity and timing.

Knowing that megadroughts hit the Sierra Nevada in the past puts recent dry and wet spells into perspective. In California, the urban and agricultural infrastructure is built on the assumption that winter precipitation for the last 160 years is representative of "everything Mother Nature has to throw at us," says Scott Stine, a professor emeritus at California State University, East Bay, who published a seminal paper in 1994 on megadroughts.

"If we take just a slightly longer view of things, we see that this whole urban and agricultural infrastructure, so dependent on water, is something of a chimera. It is not sustainable in the long term."

High Country News Classifieds
  • NORTHEASTERN UNIVERSITY
    All positions available: Sales Representative, Accountant and Administrative Assistant. As part of our expansion program, our University is looking for part time work from home...
  • COMMUNICATIONS ASSOCIATE DIRECTOR
    Position Title: Communications Associate Director Location: Flexible within the Western U.S., Durango, CO preferred Position reports to: Senior Communications Director The Conservation Lands Foundation (CLF)...
  • HISTORIC HOTEL & CAFE
    For Sale, 600k, Centennial Wyoming, 6 suites plus 2 bed, 2 bath apartment. www.themountainviewhotel.com Make this your home or buy a turn key hotel [email protected]
  • MAJOR GIFTS OFFICER
    High Country News, an award-winning news organization covering the communities and environment of the Western United States, seeks a Major Gifts Officer to join our...
  • RUBY, ARIZONA CARETAKER
    S. Az ghost town seeking full-time caretaker. Contact [email protected] for details.
  • VICE PRESIDENT, LANDSCAPE CONSERVATION
    Basic Summary: The Vice President for Landscape Conservation is based in the Washington, D.C., headquarters and oversees Defenders' work to promote landscape-scale wildlife conservation, focusing...
  • BRISTOL BAY PROGRAM DIRECTOR
    Seeking a program director responsible for developing and implementing all aspects of the Alaska Chapter's priority strategy for conservation in the Bristol Bay region of...
  • EXECUTIVE DIRECTOR
    The National Bighorn Sheep Center is looking for an Executive Director to take us forward into the new decade with continued strong leadership and vision:...
  • EXECUTIVE DIRECTOR
    The Powder Basin Watershed Council, based in Baker City, Oregon, seeks a new Executive Director with a passion for rural communities, water, and working lands....
  • EXECUTIVE DIRECTOR
    Powder River Basin Resource Council, a progressive non-profit conservation organization based in Sheridan, Wyoming, seeks an Executive Director, preferably with grassroots organizing experience, excellent communication...
  • ADOBE HOME
    Passive solar adobe home in high desert of central New Mexico. Located on a 10,000 acre cattle ranch.
  • EXECUTIVE DIRECTOR
    Eastern Nevada Landscape Coalition, based in Ely, Nevada is looking for a new executive director to replace the long-time executive director who is retiring at...
  • STEVE HARRIS, EXPERIENCED PUBLIC LANDS/ENVIRONMENTAL ATTORNEY
    Comment Letters - Admin Appeals - Federal & State Litigation - FOIA -
  • LISA MACKEY PHOTOGRAPHY
    Fine Art Gicle Printing. Photo papers, fine art papers, canvas. Widths up to 44". Art printing by an artist.
  • LOG HOME IN THE GILA WILDERNESS
    Beautiful hand built log home in the heart of the Gila Wilderness on five acres. Please email for PDF of pictures and a full description.
  • CARETAKER
    2.0 acre homestead needing year-round caretaker in NE Oregon. Contact [email protected] for details.
  • SEEKING PROPERTY FOR BISON HERD
    Seeking additional properties for a herd of 1,000 AUM minimum. Interested in partnering with landowners looking to engage in commercial and/or conservation bison ranching. Location...
  • COPPER STAIN: ASARCO'S LEGACY IN EL PASO
    Tales from scores of ex-employees unearth the human costs of an economy that runs on copper.
  • EXPERT LAND STEWART
    Available for site conservator, property manager. View resume at http://skills.ojadigital.net.
  • CONSERVATIONIST? IRRIGABLE LAND?
    Stellar seed-saving NGO is available to serious partner. Package must include financial support. Details: http://seeds.ojaidigital.net.