DECEPTION ISLAND, Antarctica — While walking beside the ruins of an old whaling station at this popular tourist stop, a unique aspect of visiting Antarctica is immediately apparent.

There are no authorities like park rangers around to keep an eye on things. Only tour guides and our consciences can keep us from damaging these decaying structures or getting too close to the seals and penguins on the dark-brown cinder beach of this volcanic island. Graffiti on oil tanks and on an old airplane hangar indicates that not everyone who has stopped here has respected the ruins.

There are no binding limits on the number of people who can visit sensitive areas in this remote wilderness. With the number of visitors reaching new highs in recent years, some environmental groups have been pushing for regulations on how many people can visit each year.

Discussions about limiting Antarctic tourism have been raised since the 2001 Antarctic Treaty Consultative Meeting, and the topic was brought up again at this year's annual meeting, in June in Edinburgh, Scotland.

The Antarctic and Southern Ocean Coalition, which supports regulations, said at the meeting that nothing has been done in almost five years of discussions.

"Antarctic tourist numbers are increasing steeply and appear likely to continue increasing steeply," the organization stated. "Presently, nothing is in place to prevent these numbers — already above 26,000 — reaching high tens of thousands within 10 years."

Alan Hemmings, a senior adviser to the ASOC who attended the June meeting, says limits need to be established — before it's too late.

"Whilst most people, and most operators, will do their best to minimize impact, that is all they are doing — minimizing it, not avoiding it," Hemmings said in an e-mail response to questions about Antarctic tourism.

But Denise Landau, executive director of the International Association of Antarctic Tourism Operators, said the number of tourists is far from overwhelming, and tour operators have become far more sophisticated in how they conduct trips. She points out that her organization works very hard to make a unique part of the world accessible to people in an environmentally responsible way.

"We do look after the place and we do care about it, so it's growing but it's not at a point now where it's not manageable," she said in a telephone interview.

A key part of the debate is Antarctica's unique political situation. The continent is governed by the Antarctic Treaty System, which has been in effect since 1961. The treaty designates Antarctica as a natural reserve dedicated to peace and science.

More than 40 nations, including the United States, have agreed to the treaty. Although different countries have research stations and bases in Antarctica, no single nation has control over any section of the continent.

Back when the treaty was signed, tourism was almost nonexistent. It has grown over the past 50 years, from a few hundred a year to more than 26,000, according to IAATO.

About 80 outfitters are voluntary members of IAATO, which was founded in 1991 to advocate and practice safe and environmentally responsible private-sector travel to Antarctica.

"To date, private-sector Antarctic tourism has developed as a remarkably low impact and cooperative model," Landau said in a statement at the meeting in Edinburgh. "Thousands of people have been able to experience and appreciate the Antarctic wilderness, with much less environmental impact than in any other part of the globe."

The group has established procedures and guidelines for trips. They include regulations and restrictions on how many people can go ashore at one time, staff-to-passenger ratios and guidelines for activities while ashore. Procedures set up by the group also call for reporting both before and after visits. IAATO operators also report environmental concerns.

Landau said many operators in IAATO revere Antarctica and wouldn't do anything to cause it harm.

"If it was a huge problem, we'd be the first ones to scream and yell," she said. "They want to protect the places that they're visiting."

During a December trip with IAATO-member Quark Expeditions, trip organizers were careful to emphasize how about 100 passengers should conduct themselves on shore. We were reminded during lectures — and even with a staff-produced play — that we must not get too close to wildlife. Staff members always accompanied us on landings.

Once, during the trip, when a group of crabeater seals on a chunk of ice appeared agitated by our approach on an inflatable boat, the steersman immediately recognized it and withdrew.

For the most part, though, many penguins and seals we encountered didn't appear too bothered by our presence. It wasn't uncommon to see penguins waddle within several feet of human visitors. But penguins could be startled. A sudden, too-close approach could scare a penguin into reversing its direction from a group of nests to the closest water.

Tourists have taken note of the impact rising numbers of visitors could have in the future.

"I wanted to see it hopefully in its more unspoiled manner than what we may get 10 years from now," said Marla Shelton, of Rochester Hills, Mich. "There have been a few places that I would liked to have gone before they got totally touristed out."

A rising concern for Landau and environmental groups is outfitters who conduct trips to Antarctica without being members of IAATO. "We're not so worried about the growth," Landau said. "We're just worried about the new parties."

Hemmings is concerned tourism will continue to grow at a much steeper annual increase than in the recent past. Among other factors, he said, the Oscar-winning film "March of the Penguins" could boost tourism further. Hemmings said a film about explorer Ernest Shackleton raised tourism numbers "quite quickly and appreciably."

Hemmings said another concern is that tourists want to go to interesting biological sites. Despite the large size of Antarctica, Hemmings said such areas are limited, because only about 2 percent of Antarctica is seasonally ice-free.

Still, Hemmings isn't opposed to tourism, and ASOC isn't set on a particular number of people who could visit each year.

"Whatever the number ... one would need to partition it sensibly between regions," Hemmings said.

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