The educational component is important, Ms. Jewell said, because shifting climate conditions at significant American sites like Sequoia National Park, Joshua Tree National Park and Glacier National Park are endangering the very things those parks are named for.
Andy Biggs, who has led photographic safaris in Africa and other remote places for 15 years, said that while some of his clients are looking for a photographic trophy, others want the chance to experience the destination the way it is now. They want to see pristine places and threatened species, he said.
A survey of visitors to the Great Barrier Reef, off the coast of Australia, found that nearly 70 percent said their desire “to see the reef before it’s gone” was the primary reason for their journey.
Marilyn and Paul Schlansky of Cape Cod, Mass., said they liked to travel off the beaten path to destinations like Myanmar and Mongolia, where the cultures are changing. “It’s hard to predict when something will disappear,” Mr. Schlansky said. “You’re not sure how much is changing until you show up.”
On trips with the travel company Overseas Adventure Travel, the Schlanskys have gone on “Day in the Life” excursions that included making yogurt tea in a yurt, collecting dung for fuel and weaving. Local tour guides also take time to point out how modernity is creeping in, seeing how, for example, plastic water bottles have been collected and used as building materials.
Travelers want to do more than witness the habitats and ways of life that are changing, Mr. Sankhala said, so they seek out immersive experiences like eating in someone’s home rather than in local restaurants. “They don’t want to just look at a monument,” he said. “They want to meet people attached to the history of that monument.”
Melissa Bradley, who runs the boutique travel agency Indagare in New York, said she has taken small groups to destinations including Namibia, Rwanda, Bhutan and Madagascar. “It’s magical to feel like an explorer, and that’s a harder experience to come by now.”
When a new destination opens or gains popularity, some travelers want to visit, before others discover it and change the destination’s flavor, she said.
Ms. Bradley said she took a group to Iran. “People would come up to us on the street to ask about our lives and talk about their own,” she said. Going to a place where authentic exchanges between cultures are still happening is a prize for travelers, she said.
Crowds can descend quickly. The number of foreign visitors to Iceland grew to about 1.8 million from about a million between 2014 and 2016, according to the Icelandic Tourist Board. About 4.7 million tourists visited Cuba in 2017, a significant increase over the previous year, despite hurricane damage in September. Mr. Austin said his clients want to get to Cuba “while it’s still kind of raw.” Ms. Bradley said that “some people feel like they already missed it.”
While heaps of tourists can hasten a natural area’s decline, Mr. Sankhala said tourism can be an important source of revenue in isolated areas. Tourists interested in remote destinations are typically also the kind who want to visit in a way that still promotes “conservation, sustainability and a low carbon footprint,” he said.
Countries can also control the number of visitors and their impact. Costa Rica’s ecotourism industry is a great example of this, Mr. Austin said. “They use their popularity to bring in funds while still preserving habitats and ecosystems.”
“We have seen a huge increase in the number of people traveling to places on the cusp of great change,” Ms. Bradley said.