Story last updated at 8/31/2011 - 2:46 pm
As a young boy, Jim Baichtal collected rocks. But it wasn't enough to just find and identify them. "I started asking why the rocks were there," he says.
Today, as a geologist with the U.S. Forest Service, Baichtal is still asking why. He spends much of his time studying what lies beneath the surface of the Tongass, especially a distinctive topography called karst, in which the bedrock is primarily soluble limestone. As heavy rain seeps through the forest floor, it becomes acidic and dissolves parts of the limestone, creating complex underground drainage systems and caves. On the surface, karst lands are characterized by cave entrances, sinkholes, and rocky beachfronts with dished depressions and sculpted spires.
"The karst here is a beautiful blend of how geology has a direct effect on everything it touches, from the plants to the water to the critters that live in and on it," says Baichtal.
Some of the biggest trees in the Tongass grow on karst. The roots penetrate into the fissures of the limestone, which provide for excellent stability as well as drainage. The limestone also buffers the chemical makeup of the surface water so it's no longer acidic when it enters the karst stream systems. Once underground, the water stays a cool temperature, and aquatic organisms like insects and salmon thrive. Studies suggest that aquatic communities associated with karst are six to eight times greater in biological productivity than those in non-karst areas, and this abundance works its way through the food web to eagles, bears - and people. Evidence of early humans has been found where underground karst streams emerge along the coast.
Cave excavations in the karst lands of the Tongass have also changed what people think Southeast Alaska looked like during the last ice age, and Baichtal says he's honored to be a part of these findings. With the discovery of human remains 10,300 years old and animal bones older than 41,000 years, says Baichtal, "We now know that vast areas of the outer continental shelf were never covered by ice. The idea of a coastal migration route for the first North Americans arriving from Asia and traveling south down the continent has now gained acceptance."
"I like to interpret the land that people live on in a manner they can understand," Baichtal says. To that end, he helped design the Beaver Falls Karst Trail on Prince of Wales Island. The falls, discovered by Baichtal, drop 40 feet and disappear into a nearby cave. An interpretive boardwalk trail takes visitors through muskeg and forest and past sinkholes and collapsed channels on the way to the falls.
"I feel a strong responsibility to carry on the legacy of Teddy Roosevelt, Gifford Pinchot, and others who created the national forest system," he says. "The national forests belong to everybody, and people who will never come to the Tongass want to know it's being managed in a good way."
Amy Gulick's book "Salmon in the Trees: Life in Alaska's Tongass Rain Forest" was published by Braided River in 2010. A photography exhibit associated with the book is currently touring Southeast Alaska in celebration of the 2011 International Year of Forests. The exhibit will be on display in Craig at the Craig High School through Sept. 19. For more information, visit www.salmoninthetrees.org or www.myalaskaforests.com.