WITH nearly 600,000 people touring Mammoth Cave every year, one of the most pressing problems here - believe it or not - is lint.
``The lint off our clothes is atrocious,'' says Joy Lyons, chief of program services at Mammoth Cave National Park in southern Kentucky. ``It congregates all along the cave trails and on cave formations.''
Tours of Mammoth Cave - the longest cave in the world - date back to 1816. Through the decades, sightseers have left behind a layer of fuzzy lint that obscures cave formations and could cause permanent damage.
``The decaying lint will create acids that etch the formations,'' says Rick Olson, a scientist at the cave. ``It also provides a food source that introduces nonnative species, such as mites.''
Mammoth Cave has one of the worst lint problems in the country, according to Mr. Olson. A lint-cleaning program may be launched soon, bringing in volunteers to brush and tweeze the fuzz off age-old rocks, stalagmites, and gypsum formations. Carlsbad Caverns in New Mexico and other commercial caves have already made such expeditions a regular part of cave maintenance.
Wisconsin caver Steve Petruniak was part of a recent lint-picking crew at Carlsbad. ``The lint was so thick it was rolling off the rocks,'' he says. ``Sometimes you would see dust bunnies like in your dryer at home.''
Mr. Petruniak, who is a member of the National Speleological Society (NSS), also spent a week last month here in Kentucky doing maintenance projects at Mammoth Cave.
During the busy summer months, close to 4,000 people a day tromp through Mammoth Cave on guided tours. Minimizing the human impact on the sensitive cave ecosystem is a top priority.
Petruniak donned a wet suit and braved the chilly waters of Mammoth's River Styx, hauling up old wood and other human-introduced debris. About 30 other NSS members - volunteers from seven states - trekked up to two miles through the cave's dark, muddy corridors to deposit the trash above ground.
``Approximately $20,000 in labor has been donated this week,'' Olson says. The volunteers supply their own food, transportation, and cave equipment. The payback comes in the form of special evening trips through the cave. ``We are all cavers. The idea of getting into places that other people don't get to see is appealing,'' says Norm Rogers, a volunteer from Peoria, Ill., who has participated in the program since it began in 1989.
Through the course of the week this year, the NSS volunteers cleaned graffiti off cave walls and ceilings, improved trails throughout the cave, and installed bat gates to protect the endangered Indiana and Grey bats that live here.
The job of counteracting past misuse of the cave, protecting endangered cave-critters, and reducing damage from modern use is a constant battle. ``The Park Service has a dual mandate to provide for the enjoyment of the visitors and simultaneously protect the resource,'' Olson says.
The balance between these mandates has shifted perceptibly in recent years. ``US taxpayers think they should have almost un-limited access to their own national parks,'' Ms. Lyons says. ``But the cave comes first.''
About five years ago, the number of people in each tour group was capped at 100 in an effort to gain more control and minimize damage. ``We have to provide resource protection somehow,'' Lyons says. ``With 300 people, there was no way I could guarantee what was going on between me and the ranger at the back of the group.''
``People still manage to get their names scratched into the wall, even with only 100 people in groups,'' notes Michael Adams, chief of interpretation and visitor services.
More than a decade ago, the United States Park Service established a toll-free telephone number for tour reservations. Today, between 35 percent and 50 percent of visitors use the reservation system. Still, vacationers are often disappointed to arrive at the park and discover that cave tours are sold out for hours.
``I understand the aversion to making advance plans to visit a national park,'' Mr. Adams says. ``It's not part of our wilderness tradition in this country. We just like to go and experience. But it is designed to help us manage access in a more equitable way.''
While trying to accommodate as many visitors as possible, the Park Service is now more willing than ever to set strict guidelines. ``In previous decades, providing service to visitors was the priority,'' Olson says. ``But we have come to realize that if we're not careful, there will be nothing left to see.''
Yet there is still a reluctance to come on too strong. Despite a continuous problem with graffiti in Mammoth Cave, for example, there are no signs warning that it is a federal offense to deface the cave. ``The Park Service shrinks from negative signage. They would rather take a positive approach,'' Olson explains.
Guides, or ``interpreters'' as they prefer to be called, talk about the issue at the beginning of all tours. ``But that's it,'' Olson says.
Others favor a more aggressive approach. ``I think they should let people know it's a federal offense - put up signs inside the cave or as you enter the park,'' Petruniak says.
The Park Service recognizes that basic human nature is at play here. ``What people are trying to do is achieve immortality,'' Olson says. ``It's not that they are malicious. They are just on vacation and having a good time. They don't understand that this wall is extremely ancient - at least a million years old.''
So cave officials fight back with subtle, but often effective, solutions. Rock borders keep most people away from walls. And strategic lighting is used in areas where historic graffiti is being preserved. ``If you see something on the wall, you're much more likely to add your own graffiti,'' Adams explains. So low-intensity, ankle-level lights have been placed in areas with historic graffiti.
As a tour group approaches Little Bat Avenue, the guide at the front turns on lights just to illuminate the pathway. The group moves through, oblivious to the hidden graffiti all around them. Under a flashlight, names with dates going back to the 1800s show up on the walls and ceiling.
``This graffiti is now considered a cultural resource,'' Olson says. ``You get an idea of where people came from and what parts of the cave they visited in what season. It helps with historical research.''
About 40 years ago, restrooms were installed in the cave, a strange juxtaposition of modern sinks, toilets, and faucets against ancient rock. The well-lit private areas became a favorite spot to carve a name and date. Every inch of ceiling and wall was covered with markings until last month's NSS crew came through. They spent three days rubbing the rock surface with vinegar to clean off the graffiti.
``We would like this to be the last time that this ever has to be done,'' Olson says. ``Caves are a nonrenewable resource. We can smooth out the graffiti. But the cave walls end up being altered by those acts of vandalism.''
``I've worked here for 15 years, and you won't see my name down there,'' Lyons says. ``I have children who are 10 and 6, and I want very much for them to have a good cave experience and then be able to bring their own children for the same thing some day.''