In January, the Coral Princess, a ship with 2,000 berths and a crew of nearly 900, plowed through the frigid waters off the Antarctic Peninsula, cruising past icebergs, glaciers and mountains clad in snow. The cruise, which had been advertised at less than $4,000 per person, is remarkably cheaper than most Antarctic expeditions, which often charge guests at least three times that amount for the privilege of visiting one of the wildest parts of the planet. Visitors to the region — and the ships that carry them — are growing in number: Antarctica, once accessible only to well-funded explorers, is now edging toward the mainstream.

But managing tourism is a tricky issue in this distant region where no individual government has the power to set the rules, and the challenge is becoming more complex as Antarctica’s popularity grows. During the current austral summer, which runs from roughly November to March, visitor numbers to Antarctica are expected to rise by nearly 40 percent from the previous season. Some observers warn that such rapid growth risks imperiling visitor safety and adding pressure to this fragile region, which is already straining under the effects of climate change, commercial fishing for krill, toothfish and other species, and even scientific research.

Human activity in Antarctica falls under the governance of the Antarctic Treaty system, a model of international cooperation that dates to the Cold War era. But day-to-day management of tourism is regulated by the tour operators themselves, through a voluntary trade association that sets and enforces rules among its members. Observers agree that this system has worked well since it was set up in the 1990s, but some worry that booming tourist numbers could push the old system to a breaking point. They say that the consultative parties to the Antarctic Treaty system — governments like those of the United States, France, New Zealand, Argentina and some two dozen others — must act more quickly to manage tourism, and protect the region’s value as a wilderness.

“The bottom line for us is that there aren’t a lot of hard rules governing tourism. It’s mostly voluntary,” said Claire Christian, executive director of the Antarctic and Southern Ocean Coalition (ASOC), a network of more than 15 conservation groups that serves as an observer to the Antarctic Treaty system. “Right now, there is a lot of good will. But that’s not something you can guarantee.”