Numerous helicopter flights and the construction of a road crossing the Iguazu National park in Brazil, with its stupendous waterfalls, lush vegetation and many endangered species including the giant otter and the giant ant-eater, are disturbing the park’s natural processes, according to conservationists.

Wyoming’s Yellowstone National Park, with its stunning collection of more than 3,000 geysers, fumaroles and hot springs, and wildlife including grizzly bears, wolves, bison and American elk, is under year-round pressure from visitors.

Conservationists in India say that two bridges currently under construction threaten the stability of a group of Dravidian temples and palaces at Hampi, site of the last capital of the last great Hindu kingdom of Vijayanagar—conquered by the Moslems in 1565.

These four locations share another dubious distinction:
They are among the 19 sites most recently listed by the United Nation’s World Heritage Committee as endangered.

The threats are numerous—almost all related to people and development, one of the most common being simple overuse by visitors.

“The travel and tourism industry is the world’s biggest, and it is growing at a fast pace,” said a spokesman for the Paris-based World Heritage Committee, whose list of places of special natural and cultural importance includes hundreds of locations around the world. “What will be the cost of this tremendous boom to the integrity, the very survival perhaps, of our heritage sites?”

World Travel and Tourism Council statistics show that in the Asia-Pacific region alone, revenues of U.S. $805 billion in 1995 will grow at an annual rate of nearly 80% over the next decade, by 2005 reaching U.S. $2 trillion—nearly twice the economic output of the United Kingdom.

These dollars can be both a blessing and a curse for endangered sites: a blessing because local governments may be encouraged to support conservation efforts; a curse because those same efforts may be overwhelmed by the sheer weight of humans pressing footprints and tire-tracks into the landscape.

Winding up on the World Heritage Committee’s list of sites “in danger” is a distinctly mixed blessing. A site’s endangered status raises its profile and may result in special attention being paid in the form of additional conservation efforts by governments and private or non-profit sources. But it can also be the first step in “de-listing” a site from the committee’s main roster of places deemed to be of extraordinary cultural or natural value.

Currently a total of 630 sites are carried on the main World Heritage List. They range from the world-famous pyramids of Giza, Zimbabwe’s Victoria Falls and Australia’s Great Barrier Reef to such lesser-known places as a 3rd-century B.C. Thracian tomb in Bulgaria, rock art in Libya, and the ruins of the 5th-century Sri Lankan city of Sigiriya.

These sites all have been singled out for their great importance not only to the countries in which they are found, but to all humankind, under an international treaty—the Convention Concerning the Protection of the World Cultural and Natural Heritage. This pact, adopted in 1972 by the United Nations Educational, Scientific and Cultural Organization (UNESCO), now has 158 signatories—the most recent being Chad and Israel, both of which joined last year.

The treaty had its origins in 1959, when international concern arose over Egypt’s decision to build the Aswan High Dam, which would flood the valley containing the ancient Abu Simbel temples. A UNESCO campaign resulted in accelerated archaeological research in the areas to be flooded, and the dismantling of the Abu Simbel and Philae temples for movement and reassembly on higher ground.

Subsequent campaigns during the 1960s led to similar efforts to conserve archaeological treasures in Venice, Italy; Moenjodaro, Pakistan; and Borobodur in Indonesia. The ultimate outcome was the 1972 treaty, under which signatory countries nominate sites for listing upon approval of the World Heritage Committee.

The World Heritage Fund, created as part of the convention and financed by a 1% share of UNESCO dues—just under U.S. $3 million per year—provides direct assistance for preserving the most seriously threatened sites.

However, the program relies mostly on the countries themselves to furnish the resources needed to preserve sites—and to raise public awareness of the dangers.

For the most part, according to a spokesman, “The countries take their responsibility very seriously.”

Eye in the Sky is a weekly series that brings you the story behind the headlines using satellite imagery, remote sensing, aerial photography, and maps. This feature is developed by National Geographic News with the sponsorship of the National Imagery and Mapping Agency (NIMA) and Earth-Info. Check out maps and imagery at http://www.earth-info.org.