Across most of the Earth, a tourist attraction that sees 35,000 visitors a year can safely be labeled sleepy. But when it’s Antarctica, every footstep matters.

Tourism is rebounding here five years after the financial crisis stifled what had been a burgeoning industry. And it’s not just retirees watching penguins from the deck of a ship. Visitors are taking tours inland and engaging in “adventure tourism” like skydiving and scuba diving under the ever-sunlit skies of a Southern Hemisphere summer.

In a remote, frozen, almost pristine land where the only human residents are involved in research, that tourism comes with risks, for the continent and the tourists. Boats pollute water and air, and create the potential for more devastating environmental damage. When something goes wrong, help can be an exceptionally long way off.

The downturn triggered by the economic meltdown created an op- portunity for the 50 countries that share responsibility through the Antarctic Treaty to set rules to manage tourism, but little has been done. An international committee on Antarctica has produced just two mandatory rules since it was formed, and neither of those is yet in force.

“I think there’s been a foot off the pedal in recent years,” said Alan Hemmings, an environmental consultant on polar regions.

Antarctic tourism has grown from fewer than 2,000 visitors a year in the 1980s to more than 46,000 in 2007-08. Then the numbers plummeted to fewer than 27,000 in 2011-12. The International Association of Antarctic Tour Operators doesn’t have final figures for the 2012-13 season, (November to March), but estimates close to 35,000 visitors.

It’s not just the numbers of tourists but the activities that are changing, said Hemmings, who has been part of some Antarctic Treaty discussions, representing New Zealand.

“What used to be Antarctic tourism in the late ’80s through the ’90s was generally people of middle age or older going on cruises and small ships where they went ashore at a few locations and they looked at wildlife, historic sites and maybe visited one current station,” he said. “But there’s an increasing diversification of the activities now so it’s much more action orientated. Now, people want to go paragliding, waterskiing, diving or a variety of other things.”

Visitors can skydive over the frigid landscape, and one group took two and three-man submarines to Ant- arctica in the latest summer.

On Ross Island, a stark black-and- white outcrop of ice on porous, volcanic rock, the active volcano Mount Erebus warns of the dangers of tourism in this remote and hostile environment. In 1979, an Air New Zealand airliner on a sightseeing tour slammed into the mountain in whiteout conditions, killing all 257 people aboard. After that disaster, sightseeing flights over Antarctica did not resume until the mid-1990s.

Some of the earliest tries at skydiving in Antarctica also ended in tragedy. Two Americans and an Austrian died in a jump in 1997 near the U.S. Amundsen-Scott South Pole Station at the geographic South Pole.

Hypoxia, a lack of oxygen, is suspected in why the skydivers failed to deploy their parachutes in time. Antarctica is not only the world’s coldest, driest and windiest continent, but also the highest.

It’s not only tourists who get into trouble. Searchers will wait until at least October to recover the bodies of three Canadians involved in research who died in a plane crash in January near a summit in the Queen Alexandra range. Hemmings said tourist ships have been involved in mishaps in Antarctica in the past five years. “Misadventure can befall anybody,” he said, but the number of tourist ships coming to Antarctica’s busiest areas was a concern.

While Antarctica is as big as the U.S. and Mexico combined, tourists and scientists mostly keep to areas that aren’t permanently frozen and where wildlife can be found. That is less than 2 percent of the continent.

It’s a land of many hazards, not all obvious. The dry air makes static electricity a constant threat to electronics and a fire risk when refueling vehicles. Residents quickly get into the habit of touching metal fixtures as they pass, and metal discharge plates are set beside all telephones and computer keyboards.

Most tourists arrive on the Antarctic Peninsula, which is easily accessible from Argentina and Chile. The next most popular destination is the Ross Sea on the opposite side of the continent, a 10-day sail from Australia. Both landscapes are intensely bright and silent during the 17 weeks between sunrise and sunset in the summer. The peninsula is a milder environment and has a wider variety of fauna and flora.

Two cruise ships visited Ross Island, connected to the continent by ice, last summer. Summer averages 21 degrees but often seems colder.

Passengers visited the largest settlement in Antarctica, the sprawling U.S. McMurdo Station, which can accommodate more than 1,200 people, as well as New Zealand’s neighboring Scott Base, which sleeps fewer than 90.

The two bases, separated by a 2-mile ice road, don’t facilitate tourism, but tourists are generally welcomed. Both have well-stocked gift shops.

Antarctic New Zealand’s environment manager Neil Gilbert said more robust monitoring is needed to track impacts of tourism. “The Ant-arctic Peninsula ... is one of if not the most rapidly warming part of the globe,” he said, adding that is unknown what impact tourism is having on an already significantly changing environment.

There are fears that habitat will be trampled, that tourists will introduce exotic species or microbes or will transfer native flora and fauna to parts of the continent where they never before existed.

A major fear is that a large cruise ship carrying thousands of people will run into trouble in these ice-clogged, storm-prone and ill-charted waters, creating a disastrous oil spill and a humanitarian crisis for the sparsely resourced Antarctic research stations and distant nations.

To reduce the risk of spills, the U.N.’s shipping agency barred the use of heavy fuel oil below 60 degrees latitude south in 2011. That was a blow to large cruise ships. But large ocean liners can comply by using lighter distillate fuels in Antarctic waters.

About 9,900 passengers are believed to have visited Antarctica on cruise ships in the season now ending, double 2011-12.

Tourists outnumber scientists and staff at national scientific research stations in Antarctica in peak summer season, though the researchers make more of an impact because they stay longer.

But Australian-based adventurer Tim Jarvis sees Antarctic tourists as part of the solution for a frozen continent where the ice is ra- pidly retreating.

If more tourists see its wonders and the impacts of climate change, particularly on the Antarctic Peninsula, Jarvis said, the world will become more inclined to protect the continent.