According to Hu Xinyu, head of Friends of Old Beijing conservation group, half of Beijing's 3,000 hutongs had been destroyed by 2003 and since then "the speed has been very fast". In Shanghai, architect Chen Guang reckons that of the historical architecture not included in the city's protection scheme, only 2-3 per cent will be left by 2010.
At the same time, both cities have developed endless suburbs studded by anonymous high-rise blocks and reached by eight-lane highways that make car ownership a near necessity.
The risk is that China's urban centres will end up looking identical to a procession of other cities around the region. "In terms of style, the building boom of the last decade has been a total failure," says Ruan Yisan, an architecture professor at Tongji University in Shanghai. "It has been a totally market-led, profit-driven, commercial exercise."
Yet conservationists in China face huge practical difficulties. With the government allocating one family to each room of old houses, many became over-crowded and in poor repair. One recently destroyed mansion in Shanghai's French Concession housed 40 families.
When the wrecking ball arrives, residents often have an ambivalent attitude to the buildings, mixing nostalgia with the desire to move to more modern surroundings with toilets and central heating. "We would love to be moved to a better flat, as long as it is not too far away," says Zhang Yi, who lives in a 1920s house behind Fuxing Road in Shanghai.
Moreover, the debate in China takes place in a very different context. For Europeans, old buildings are one of the principal ways of connecting to the past. But in China, food, dialect, or social relations can be more important.
"There is a whole western tradition of classical archaeology and visiting the Parthenon," says Lynn Pan, a Shanghai-born historian. "But there is no such tradition in China."
Against this backdrop, however, there is a growing conservation lobby, especially in Shanghai, where the government has now issued protection orders for 632 buildings. Recent achievements include preserving parts of the old Jewish area in Hongkou.
Architects point out that China is still a work in motion. As in Hong Kong, some of the worst high-rises can be replaced by better ones as the city becomes richer.
Christopher Choa, an architect who recently left Shanghai after a decade, says the energy of a city could eventually impose itself on the blander new constructions. "Inside every modern Chinese city there is an old Chinese city trying to get out," he says. "The issue is whether the lilong life will seep out into the empty spaces."
Mr Choa also argues that western attitudes to current Chinese construction mirror European responses to the 1890s boom in New York, mixing fascination with "an undercurrent of contempt for the naivety of some of the new Chinese buildings".(FTchinese.com)