Galápagos Islands, Ecuador
The giant Galápagos tortoise
(above, a tortoise near the rim of the Alcedo Volcano) is one of the many species on the Galápagos Islands that are found nowhere else on Earth.
But these unique species "are in considerable danger from irresponsible visitation by large cruise ships and inappropriate development," Tourtellot said.
Though the islands' rating on National Geographic's Destination Scorecards has improved slightly in recent years, the area is "still very much on the cusp," he said.
"When you visit the Galápagos, make sure you're doing that with a responsible tour operator."
The volcanic archipelago, about 600 miles (965 kilometers) west of mainland Ecuador
, was named one of the 28 finalists in the New7Wonders of Nature contest on July 21, 2009.
Photograph by Sam Abell, NGS Image Collection