Kaiping, China (CNN) -- In a quiet corner of southern China's Pearl River Delta, hundreds of abandoned watchtowers dot a landscape of water-logged rice paddies, lush bamboo groves and ancient villages.
Bristling with battlements and turrets, the ornate towers were built by families and villages in need of protection during the late 19th and early 20th centuries when much of the country was controlled by warlords and banditry was rife.
Now a UNESCO world heritage site, these days the Kaiping watchtowers, or diaolou as they are known locally, face a threat of a different nature -- the incredible boom in Chinese tourism.
The tiny village of Zili, which has the largest collection of towers, attracts dozens of tour buses on weekends. Their passengers are ushered around the towers by guides sporting red flags and microphones rigged up to loud speakers.
They chase the skinny chickens that roam about the dirt paths, snap photos, sample "peasant family food" and buy rustic bamboo souvenirs, while the village's few remaining elderly residents sit on small plastic stools and look on bemused.
It's a scene that's played out at other UNESCO sites across China, where world heritage status is increasingly being used as a economic vehicle to develop backward regions, says Chris Ryan, a professor of tourism at The University of Waikato in New Zealand.
"The idea behind having this status is that there are conservation, preservation and restoration issues, where in China it seems to be primarily geared toward promoting tourism and its economic benefit," says Ryan, who has studied Kaiping and another world heritage site in Anhui province, eastern China.
According to Ryan, Chinese made 2.6 billion trips last year, up from just over a billion seven years ago and numbers are expected to rise further.
"Places that were previously very remote and didn't see a lot of tourists are now seeing enormous numbers arriving because they have the money to travel," says Neville Agnew, group director of the Getty Conservation Institute, which has worked in China since 1989.
"It's an interesting phenomenon because it's in complete contrast to the experience in Egypt, where almost all the visitors are foreigners."
China now has 43 world heritage sites, the most of any country in the world. Dozens of other wannabe UNESCO sites across China are preparing bids.
Jing Feng, the Paris-based chief of UNESCO's Asia and Pacific section, says that the prestige of world heritage inscription always means an increase in visitor numbers but acknowledges the pressures of mass tourism in China are particularly acute.
"People are getting richer and they have the right to appreciate heritage sites but we need a balance," he says.
Tackling the problem is difficult. Jing singles out Lijiang, an ancient town set in a dramatic mountain landscape in the southwestern province of Yunnan, as a place that has struggled to accommodate a surge in tourists.
Designated a world heritage site in 1997, the town, home to the matriarchal Dongba culture, now receives 11 million visitors a year and conservation experts have been shocked by the level of commercialization.
Locals have moved out of the city's ancient core, renting their homes out to businesses.
Jing was part of a UNESCO monitoring mission to the town in 2008 and local authorities have pledged to improve visitor management and shut the discos and karaoke bars that had sprung up.
However, a doubling of admission ticket prices in a bid to reduce visitor numbers has had little impact and officials aim to increase visitor number to 16 million by 2015.
UNESCO has only twice removed world heritage sites from its list and Jing says there is little chance, for now at least, that any Chinese sites would lose the designation because authorities had put forward "corrective measures."
Poor, rural areas bypassed by China's recent economic boom are those most keen to secure world heritage status, says Han Li, who works for the Global Heritage Fund in China.
Local officials often take out huge loans to build infrastructure to prepare their bid, she says, and local people, at least, initially welcome the opportunity to find work outside farming or as alternative to migration.
"Having world heritage status definitely changes your property values, your investment opportunities and it's a really big life-saver for a lot of these places," she says.
Officials in charge of Kaiping's watchtowers have said they aim to attract up to 2 million visitors each year, up from 100,000 in 2007 when it was first inscribed as a world heritage site with a view to generating revenues of 50 million yuan (US$7.8 million).
How this money will be spent will be key to the future of Kaiping's watchtowers.
So far, it appears that much of the money generated has been spent on car parks, ticket booths and landscaping in the four villages featured in tourist brochures.
It's not clear what will happen to the hundreds of other towers not earmarked for tourist development. They are used as barns and storage sheds or stand empty and forlorn despite their protected status.
Many were abandoned after the Communist victory in 1949 when those with overseas ties fled. More recently, villagers have left for the booming factory towns on the other side of the Pearl River Delta.
The challenge for the local authorities in Kaiping, and at China's other heritage sites, is how to manage tourists visits so that they bring maximum economic benefit without harming the heritage sites and those who live nearby.
One radical solution is to limit visitor numbers.
For example, from next year the Mogao Grottoes in remote Northwestern China plans to allow 6,000 visitors per day, down from up to 11,000 at present, says Agnew at the Getty Conservation Institute.
The move follows fears that the moisture from visitors' breath and sweat was harming the centuries-old cave paintings and Buddhist sculptures.
But this approach is unlikely to be adopted widely, especially at living sites such as Lijiang's old town and Kaiping, where economic imperatives are most likely to trump heritage preservation.
"World heritage sites don't need to be static -- they can bring income and development," says Li at the Global Heritage Fund.
"But I think it's important to remember that heritage does have its own inherent value and it's not just about a tangible financial return."