Wonders In Trouble

Though they might seem timeless, many of the world's most treasured sites are in peril, threatened by theft, development, climate change, or unsustainable tourism.

Great Wall, China

Constructed to shelter China's people and culture from the outside world, the Great Wall stretches over 4,500 miles and took 2,000 years to construct.

But perfection isn't protection, and the Great Wall is now under threat from the pressures of the modern world.

Unsurprising given its incredible length, large portions of the wall now suffer from neglect and erosion from the elements. More popular sections are subject to the wear and tear that comes with millions of visitors each year.

The Pyramids, Egypt

In the 1990s, a highway plan that would have damaged the site was successfully thwarted, but development, rising groundwater, pollution, and theft continue to threaten the mysterious tombs, monuments, and pyramids of Memphis.

Rio Platano Biosphere Reserve, Honduras

The Rio Platano Biosphere Reserve, one of the last virgin tropical rainforests in Central America, remains—at least for now—a portrait of abundance. The mountainous landscape, which slopes down to the Caribbean, teems with wildlife, including 39 species of mammal and nearly 400 species of bird.

Human cultures, past and present, are an important part of the biosphere's riches as well: Not only does the reserve include Ciudad Blanca, an important Maya site, but the forest is home to more than 2,000 indigenous people who have preserved their traditional ways of life.

The more than 1,900 square miles of pristine rainforest are under serious threat, though.

Old City of Jerusalem, Jerusalem

The Old City of Jerusalem has been on the World Heritage in Danger list since 1982—longer than any other of the list's 38 imperiled properties.

Considered a holy city in Judaism, Christianity, and Islam, Jerusalem proves its popularity with record-breaking tourist numbers. In 2010 alone, the city hosted 3.5 million travelers, and local government hopes to welcome 10 million visitors this decade. And Old Jerusalem, with its 220 historic monuments—including the famous Dome of the Rock and Wailing Wall—is a must-see stop on the Jerusalem tourist circuit. That's a lot of pressure for a site already straining under the weight of heavy tourism and a lack of maintenance.

Everglades National Park, USA

Beautifully described as "a river of grass flowing imperceptibly from the hinterland into the sea," Everglades National Park  is a haven for rare and threatened species, including the Florida panther and the manatee, the national park comprises an astounding variety of water habitats, including the Western Hemisphere's largest mangrove ecosystem.

However, the very life source of its riches—the aquatic ecosystem—is in peril. Years of draining, dike building, and construction have reduced water inflows by up to 60 percent and destroyed more than half of the original Everglades.

Petra, Jordan

Once a thriving trade center for frankincense, myrrh, and spices, the ancient city of Petra continues to attract curious visitors in search of beauty and cultural riches. The ruins of the city, which was half built and half carved into red sandstone cliffs, hold architecturally elaborate tombs along with temples, sacrificial altars, and even a Roman-style amphitheater.

But while beautiful, the red sandstone is soft and easily eroded. The dramatic rise in visitors over recent decades—from 65,000 in 1986 to nearly 1 million in 2010—is taking its toll.

Galapagos Islands, Ecuador

The Galapagos Islands have emerged on the other end, having made significant headway against the threats of "invasive species, unbridled tourism, and overfishing." However, the same isolation that made the islands a "living museum and showcase of evolution" also makes them intrinsically vulnerable to the environmental pressures of tourism and the constant threat of invasive species.

Best known for unique animal life, such as the land iguana and giant tortoise, the Galapagos are a point of pilgrimage for wildlife lovers. But our presence changes the landscape: In the islands' relatively short history of human settlement, it's estimated that about five percent of the Galapagos' species have become extinct

Angkor, Cambodia

The 150-square-mile Angkor Archaeological Park protects just a part of what was once a vast cluster of ancient capitals in the jungle of Cambodia. Its best known site, Angkor Wat, remains even today the world's largest religious building.

In 2004, after pillaging and landmine problems were successfully tackled, but it remains at risk. The dramatic rise in visitors—from zero during the dangerous '70s and '80s to 640,000 foreign visitors in the first three months of 2012 alone—has taken its toll on the buildings and temples.

Great Barrier Reef, Australia

It's the world's most extensive coral-reef ecosystem, home to 400 types of coral, 1,500 species of fish, and 4,000 types of mollusk. The Great Barrier Reef draws visitors to Australia from all over the world, but climate change is threatening the very framework of the remarkable living marine system.

As ocean temperatures rise and waters become more acidic, the Great Barrier Reef is expected to be "subjected to increasingly frequent bleaching events, cases in which corals turn white and may die."

Machu Picchu, Peru

2011 marked the 100th anniversary of the rediscovery of Machu Picchu. In the last century, the Inca ruins have become one of the world's most famous tourist attractions. And as the journey to see the "Lost City" has grown easier with the addition of train service, its remote location high in a cloud forest of the Peruvian Andes hasn't been able to shield it from the damaging effects of extreme popularity.

Uncontrolled development, erosion, and the ongoing risk of landslides that could wipe out the site keep Machu Picchu's future at risk.