As China becomes increasingly urbanized  , it has to find space for its urban and rural citizens as both groups become increasingly integrated. Experts suggest a possible model way may be "re-inventing" a "garden city". China's mega-cities are bursting at the borders and the country is now undergoing the quickest and biggest urbanization in the history of mankind. It is estimated that by 2025, China will have 400 million more people living in its cities, raising its urban population to 900 million. Besides, new satellite towns are mushrooming on the urban fringes while city ring roads are rippling outwards into the countryside at amazing speed. Satellite maps collected by Professor Joshua Bolchover at the University of Hong Kong bring the problem sharply into focus. They track the changing rural-urban framework in the past 30 years, and suggest that cities are cruelly destroying surrounding rural land and rapidly reducing the amount of arable   land, which gives way to new residential blocks, new industrial zones, new financial centers and the other inevitable signs and signatures of economic growth. This, however, is not sustainable growth pattern, especially when China has the world's largest population to feed. So concerned urban planners are starting to note the social and physical effects of diaspora   when replaced rural communities are forced into the cities. On the other hand, a trend of thought is gradually taking shape and this is the concept of the "garden city", a combination of country and city that is being proposed by architects and city planners. Hua Li, from Tao Architects, is among the many professionals with such a voice. His argument is supported by a long-term study on this subject. As Hua says, the answer is to preserve patches of productive farmland within urban boundaries. Less transportation means we have fresh agricultural products at lower costs and less carbon emission in the city. And urban farmland can also be showcased for agricultural tourism and education. The concept is already practiced at the grassroot level. Agriculture has gone into the air, up to roof and balcony in some communities in the cities. It's common to see organic "hanging garden" on the roof of some traditional courtyard home. According to some people, the rooftop project translate to tangible (=" practical)" benefits, such as safe, nutritious vegetables, a cooler home in summer. Some say thanks to the tomatoes they plant that are natural insect killers, there're fewer mosquitoes. Apart from these, it also contributes to better bonding with neighbors. Zhang, a doctor in Beijing, began creating his hanging garden five years ago. Since his garden became home to 30 kinds of vegetables and fruit --- all enough to feed his family, neighbors have enjoyed dropping by for a relaxing chat or just to see how well the lovely vegetables and fruit are doing. Although people like Zhang are still rare and the greening of roof space with vegetables and fruit takes skill and energy, with more positive media exposure and advanced technology there is the prospect that garden city will become common practice in the near future. By then, cities will no longer look so gray when seen from the satellites. Some experts suggest re-inventing a "garden city" because   _  .
it is the only model way to save the cities it helps stop destroying the rural areas increasing urbanization takes place in China China has the largest population to feed