Aletsch Glacier, Switzerland

A hiker standing on the Aletsch glacier photographs an ice landscape on August 23, 2016 near Bettmeralp, Switzerland. (Sean Gallup/Getty Images)

The glaciers of the European Alps are some of the region's most treasured natural wonders—and are prime tourist destinations. But the glaciers, such as Switzerland's Rhone and Aletsch glaciers, and Austria's Pasterze glacier, are rapidly shrinking, propelling them into the global climate change stage.

The Pasterze Glacier, Austria's largest, , according to the Austrian Alpine Association's annual glacier survey. Its volume has declined by half since it was first accurately measured in 1851. In Switzerland, the Rhone Glacier has in the last decade alone. It has been covered in white blankets to slow the melting of the rapidly retreating ice for the last eight years. Another Swiss glacier, the Great Aletsch, which was around 2,950 feet thick at one point, has , and that pace is quickening, according to glaciologists. The Aletsch may lose 90 percent of its ice volume by 2100, Andreas Vieli, a professor who heads the University of Zurich's group of glaciology experts, said last year.

But while the glaciers have always attracted visitors keen to see the descendants of the icefields that shaped the Alps, an increasing number of "last-chance" tourists are also flocking to the sites to experience the glaciers before they vanish forever. Publications and travel guides have even included the glaciers of the European Alps in several must-see lists and "places to see before they're gone" and .

Also known as "doom tourism," and "climate tourism," last-chance tourism is a growing trend of tourists seeking to experience endangered sites before they disappear. While tourism provides valuable opportunities to see the world's natural and cultural treasures, it can also bring significant consequences to the destinations, especially already-delicate ones. "Promoting the vulnerability of certain threatened destinations ," according to research published in the journal Current Issues in Tourism, authored by Harvey Lemelin, et al. The authors wrote that last-chance tourism can help raise awareness on climate change but it can also help accelerate negative human impacts on nature.

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One of the most popular endangered sites for last-chance tourists is Australia's Great Barrier Reef, which has seen . A recent a research paper titled "Last Chance Tourism and the Great Barrier Reef" published in the Journal of Sustainable Tourism found that nearly 70 percent of people who visited the reef in 2015 said they . While the influx of visitors is good for Australia's $5.2 billion tourism industry, those visitors are also contributing to the reef's demise, according to Karen McNamara and Annah Piggott-McKellar,authors of the paper. "The paradox lies in tourists visiting a destination due to its perceived status of being in danger of disappearing forever, further deteriorating the destination through population pressure and on-site activities associated with tourism, as well as the carbon emissions associated with travel, adding to anthropogenic climate change," they wrote.

When visiting endangered sites, such as the glaciers of the European Alps, travel experts advise visitors to be responsible tourists.

"When it comes to visiting a 'last chance destination', it's important to choose your tour operator or mode of travel wisely," said Anthony Berklich, travel expert and founder of travel platform, . "Whether you're venturing to the Great Barrier Reef, Antarctica or witnessing the last rhinos that roam the plains of countries like Botswana—you have to take it upon yourself to be educated. How green is your tour operator? How much money or effort does your hotel put into conserving the area in which its built? What impact does your visit have on the area? These are all important questions." Some governments are excellent at conservation of their endangered destinations, some will do anything to soak up every last tourism dollar until the location is completely destroyed. Base your travel decisions on these facts and considerations, so, when you do visit, you know that you're helping the cause and not inadvertently hurting it."

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Pedersen Glacier is photographed from Aialik Bay in Alaska in 1909. (USGS/ U.S. Grant)