CANCUN, Mexico (Reuters) - Giant sea turtles have roamed the world‘s oceans since the dinosaurs walked the Earth, and they have been nesting on Mexico‘s Yucatan peninsula at least since Mayan times 2,000 years ago. But if a Spanish hotel chain has its way, the only sign left of turtles on X‘Cacel beach on Mexico‘s Caribbean coast could soon be tortoise-shell ashtrays in gleaming marble lobbies, environmentalists say. Plans by mass tourism specialists Sol Melia to develop X‘Cacel 120 km south of the bustling tourist resort of Cancun, have enraged ecological groups, which say the 2.5 km of beach are one of the last refuges between Brazil and Florida for endangered Atlantic marine turtles. Of the world‘s seven types of marine turtle, four visit the coast of Mexico‘s southeastern state of Quintana Roo — the Green, the Loggerhead, the Hawksbill and the Leatherback. Turtle specialists say X‘Cacel and its neighbouring beach X‘Cacelito are a unique habitat for Green and Loggerhead turtles. Studies have shown the turtle populations of the area are the likely source of up to 30 percent of all the genetic information of the two species in the entire Atlantic. Furthermore, the dunes where the turtles nest between mid-May and mid-September are virtually the only undeveloped piece of coastline in the central part of Quintana Roo. From Cancun south to the archaeological ruins of Tulum, the state‘s FIDECARIBE tourism agency has sold off virtually every plot. The turtles are the main concern of environmentalists. But the mangrove behind the beach also contains numerous protected species of fauna and flora including "chit" palm, black mangrove, boa constrictors, swamp crocodiles, anteaters, manatees and several other types of animals and plants. That may soon change. Despite a decade of appeals by local and international environmental groups to have X‘Cacel declared a special nature reserve, the state government quietly sold 45 ha of beachfront and mangrove to Sol Melia in February for a reported $2 million. It sold another 50 ha to a local Mexican politician and developer. A Sol Melia spokeswoman in Orlando, Florida, from where the group‘s Latin American operations are run, said the company had decided not to comment on the project because it had not yet begun construction. Sea turtles are notoriously sensitive to development. When Christopher Columbus first stumbled on what are now the Cayman Islands in the Caribbean, they were covered with the ancient creatures. Five hundred years later, there are none. Baby turtles, some born semi-blind, use the phosphorus glow of ocean waves to direct them safely to the sea. The lights of a nearby tourism development could easily disorient them, sending them the wrong way, perhaps into the gullets of predatory birds. Even a flashlight is enough to disorient an adult female turtle laying eggs, who may head toward the light and end up baking to death in the hot sun the following day. As an indication of their vulnerability, turtle experts say only one in 100 baby sea turtles makes it through the treacherous journey to adulthood. According to its critics, the Spanish hotel chain has shown little sympathy for the turtles so far. Eventually, the state government made an abandoned restaurant available for the volunteer turtle monitors. In October, Greenpeace asked Mexican environmental authorities to prosecute Sol Melia because survey work had apparently damaged protected chit palms. Aware of concerns about the environment and the turtles, the Quintana Roo state government under Gov. Mario Villanueva Madrid this year declared 100 metres in from the sea a protected area where construction was prohibited. As a result, Villanueva told local reporters, complaints about development were "a load of rubbish." But opponents argue that this narrow prohibited zone is not enough to protect the sea turtles. Under local ordinances, Sol Melia is allowed to build up to 450 rooms on its site. If other prospective developments are included, activists say it could mean up to 3,000 tourists tramping around on the beach during the nesting season, leaving litter, disturbing the dune and possibly changing the humidity and temperature of the sand, which is vital for hatching. To ecological activists, the plan is an absurdity. At the end of the day, Mexico could lose a lot by developing the site, experts say.