The number of visitors allowed to enter Machu Picchu, the most important archeological site in South America, is to be strictly limited under a new plan proposed by the Peruvian government.

The famous lost city of the Incas, in a remote valley in the Andes, has become Peru’s biggest attraction — but Unesco, which conferred World Heritage Site status on the area in 1983, has expressed concern about pollution, erosion and unfettered development the rise in tourists has caused.

The £70m plan, which will be put to Unesco at a meeting in Lima tomorrow, will impose a limit of 2,500 tourists per day. “This is about the number of current visitors, so we are preventing any further strain on Machu Picchu from the increase in tourism,” says the Peruvian embassy in London.

It remains to be seen whether the 2,500 cap will satisfy Unesco, which has threatened to place the site on its In Danger list. Speaking from Ecuador, its negotiator, Nodia Sanz, said “We are very concerned at the state of conservation. We’ll wait to see the detail of the plan before deciding on our position.”

UK tour operators have given the idea a cautious welcome. “It’s a good idea to cap it, but 2,500 is still a lot,” says Audley Travel.

“It’s a very small site. If Unesco really think there’s a conservation risk, I can’t imagine that number’s going to impress them.”

Another World Heritage Site, Cambodia’s Angkor Wat, is acting to contain its own environmental threat — cattle poo. Police chiefs have ordered a roundup of a group of 40 buffaloes and cows that are reported to be defecating freely on the ancient temples. However, visitors may have to watch their step for some time: so far, the police have caught only one buffalo.