TONGASS NATIONAL FOREST (AP) -- The cave enthusiasts have left the cold, dank recesses beneath the rain forest of Southeast Alaska. The results of their summer exploration of the underworld of the Tongass are now transferred to notebooks and memories.
But the work continues for U.S. Forest Service biologist Jim Baichtal. In the months to come, he will digest the annual research done on the vast, but little-known caves of Southeast Alaska. The latest findings will be incorporated into future timber harvest policy.
Baichtal is responsible for the 17 million acres that make up the Tongass, which stretches from Yakutat to Ketchikan. That's too large for one geologist, so every summer Baichtal coordinates caving expeditions made up of volunteers.
''Cavers have played a major role in land-management decisions out there through their discoveries,'' Baichtal said.
Spelunkers from around the world make the summer trips. Eager to discover virgin caves, they spend nights in soggy tents, wear mildewed rain gear and plow through thick forest grounds.
Beneath the ancient trees is a vast, complex system of underground waterways, canyons and caverns. These caves have changed timber harvesting practices in the Panhandle, especially since passage of the Federal Cave Resources Protection Act of 1988.
Decades of logging altered entire drainage systems and allowed hillsides to erode rapidly in a region that averages 400 inches of rain a year. The caves are closing up and choking.
In other parts of the world, some caves are kept secret from the public in order to preserve their features and keep their ecosystems intact. In Alaska, however, the fact that the caves were virtually unknown until recent years has led to their destruction.
''There's no doubt about it, our past timber management has put tons of sediment and debris in the caves, and changed the pH and water balance,'' Baichtal said.
The summer cave expeditions help guide the Forest Service in managing timber and more recently caves and other limestone formations.
For example, program volunteers discovered at least 100 caves on Kosciusko Island, off the west coast of Prince of Wales Island and 75 miles northwest of Ketchikan. Expedition leader Barbara Morgan, a biology student at the University of Alaska Southeast, said it took three Kosciusko expeditions to identify, survey and name the caves. She speculates there are at least 100 more.
The findings prompted the Forest Service to cut the amount of land available to logging for giant spruce, cedar and hemlock from 6,000 acres to 900 acres.
For its part, the logging industry is going along with the restrictions for now.
Owen Graham, executive director of the Alaska Forest Association, said loggers would rather avoid areas with caves because unseen sinkholes and 100-foot shafts can be treacherous. Road building is more challenging, making the whole operation more expensive, Graham said.
Kosciusko Island, where large-scale commercial logging began in Alaska in 1948, is about 80 percent carbonate limestone. Acidic water creeps into the stone to create channels, drainages and eventually, caves. Some of the caves contain stalagmites, stalactites, thin hollow formations called soda straws or shiny limestone deposits cascading from cave walls.
Karst, the catchall name for land features formed in limestone, is key to cave formation and forest drainage. Tree roots can grow deep into channels in the karst, allowing trees to reach their great heights in soil no thicker than two inches atop the karst.
Clear cut logging on karst alters the entire drainage system. Because the soil is so shallow, it erodes quickly.
''A fresh clear cut will put in 20 to 40 percent more water (into the caves) because you've lost all the forest canopy and interception,'' Baichtal said. ''So the systems flood where they probably hadn't flooded for thousands, if not hundreds of thousands, of years.''
This phenomenon creates potential hazards for the summer cave researchers.
Kosciusko Island is among the scores of islands of the Alexander Archipelago that are riddled with caves, canyons and other karst features. A misstep could plunge the unwary into a 50- or 100-foot holes in the ground. Cavers carry rope and climbing gear.
In their latest expedition, cavers scoured Kosciusko using a cutting-edge technology called LIDAR, which stands for light detection and ranging. Laser beams aimed at the dense forest canopy from an airplane determine topographical and underground depth with stunning accuracy. Computer-generated maps then pinpoint sinkholes and possible caves to be confirmed by cavers.
Simon Dillon of Stockport, England, was among the dozen volunteer cavers in the summer project on Kosciusko Island. He said he was drawn to Alaska for the thrill of exploring virgin caves.
''It's a caver's dream to go find new stuff,'' Dillon said. ''We're finding unique karst features that will save the trees. I've never, ever seen a place anywhere like this. It's just vast amounts of holes in the ground.''
These holes contain clues that have altered migration theories. A brown bear skull dating back almost 12,000 years on Prince of Wales Island proves that brown and black bears lived on the island simultaneously. There are no brown bears on Prince of Wales Island now. On Dall Island, a brown bear skull and leg bone dating back 12,300 years were found in Enigma Cave in 1994.
On the last day of this summer's three-week expedition, cavers were in the midst of surveying a new find but had to stop. A rock dropped down a vertical shaft fell for the count of six seconds, too deep to explore without more surveying.
What lies below will remain a mystery until next year.
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