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The earth is warming, glaciers are receding and oceans are changing. As a result, habitats are shrinking and species are dying -- and many tourists want to see them before they disappear.

As scientists have studied and described the Earth's transformations, some more recent and rapid than others, their observations have given way to a phenomenon dubbed "doomsday tourism." The concept is simple: Travellers seek out imperiled destinations and try to experience their grandeur before they vanish.

The trend is best embodied by a surge in the number of travellers to the Gal�pagos Islands and Antarctica, both besieged by changes to their ecosystems.

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In 1990, the Gal�pagos Islands welcomed 40,000 visitors. By 2006, that number had reached 145,000, according to the Gal�pagos Conservancy. The International Association of Antarctica Tour Operators estimates that 34,000 people will visit the land mass this year, more than four times the number of tourists there 15 years ago.

But these environmental poster-child destinations are not the only ones to feature a unique habitat facing imminent threats. Several nonprofit and non-governmental organizations, including UNESCO, Conservation International and the World Wildlife Fund, have begun cataloging threats to the environment and affected areas, and the results are surprising.

"They don't all have mass tourism," says Dr. Sanjayan, lead scientist at the Nature Conservancy, "but every one of these places attracts a lot of visitors because they're so unique."

Defining What's Endangered

The Nature Conservancy, an Arlington, Va.-based conservation organization, has created a "global conservation atlas," scheduled for public release in mid-2009, which is designed to draw attention to and protect the planet's most vital habitats: oceans and coasts; lakes and rivers; deserts and arid lands; grasslands; and forests. Sanjayan and his fellow scientists also wanted to spotlight habitats that are unconventional candidates for preservation, such as grasslands.

The Nature Conservancy's list of endangered destinations includes the Sonoran & Chihuahuan desert borderlands, the Patagonian grasslands of Argentina and the Great Lakes in the U.S. and Canada. In these places the threats range from rapid population growth to invasive species to land use practices. Also on the list are the arid lands of Namibia, the Appalachians, and stretches of the West Indian Ocean coastline.

Travellers looking to explore these places have numerous options. The National Geographic Center for Sustainable Destinations, a Washington, D.C.-based organization that promotes thoughtful forms of tourism, has created innovative maps for visitors to Mexico's Sonora desert and the Appalachians. The maps feature not only attractions like wildlife refuges and state parks, but also recommendations on local cultural events, food vendors and eco-friendly hotels and resorts.

In the Sonora desert, for example, tourists can visit the Northern Jaguar Reserve then stay with a local family at the El Ranchito de Hu�pac and learn how to make white cheese. In the Appalachian Mountains, visitors can choose from dozens of nature-based attractions, including Seneca Rocks, a towering quartzite rock formation in West Virginia, and Kentucky's Mammoth Cave National Park, where the world's longest cave is located.

Opportunities to experience nature are abundant in the other endangered destinations selected by the Nature Conservancy. The Seychelles and Mozambique, both on the West Indian Ocean coastline, boast coral reefs, estuaries and mangrove and mist forests. Several tour operators, including REI Adventures and Classic Journeys, offer hiking trips through Argentinean Patagonia, where the grasslands are home to unique species like the guanaco, rhea and gray fox.

Vibrant Today, Gone Tomorrow?

These may be vibrant destinations now, but scientists warn that extreme changes to the environment can happen incrementally and are often invisible to the naked eye.

In Joshua Tree National Park scientists from the National Parks Conservation Association are worried that the area's iconic tree, which draws an average of 1.3 million visitors a year, may eventually stop growing. Mark Wenzler, director of clean air and climate programs for the D.C.-based advocacy organization, says that rising temperatures are preventing Joshua trees from releasing seeds, which happens at night when the temperature drops below freezing.

While climate change is often given as an explanation for why the Earth's landscapes are transforming, scientists say the answer is much more complicated.

"Climate change is a natural process for Earth," says R. Brooks Hanson, deputy editor of the journal Science. Hanson notes that the Earth has endured swift temperature changes before, but that scientists have never observed the acceleration they see now since temperatures were first recorded. "We're tweaking the natural system, and it is responding," he says.

Such alterations are due not only to global warming, but also to human behaviour like overfishing, pollution, habitat destruction and water diversion.

Ethical Doomsday Tourism

All of this raises the question: Is it appropriate, or even ethical, to travel to threatened destinations?

Many argue that travel to these places is acceptable provided that it's done responsibly. The World Travel & Tourism Council, a London-based forum for business leaders, advocates for a sustainable approach to tourism in which the destination's resources are protected for long-term viability. Amir Girgis, an economist with the council, says this includes everything from building environmentally friendly hotels to a government that offers incentives for businesses that practice sustainable tourism.

Boundless Journeys, a Vermont tour operator, tries to adhere to these principles when taking clients on trips to the Gal�pagos Islands, Palau and Nepal. Karen Cleary, the company's destination manager, says trips are done in groups no larger than 16 people and that they seek out eco-friendly accommodations.

Cleary says that her clients have yet to express an interest in visiting destinations viewed as endangered. She does note, however, that the company's trip to Iceland, where many of the glaciers are receding, has performed better than ever, selling out for two consecutive years.

"We try not to capitalize on those kinds of trends," says Cleary. "I think we stick to our philosophy that travel is important, mind-opening ... and we try to do it in a manner that has as small an impact as possible."