In recent years, rural to urban migration has been more prominent. In this context, latest estimates suggest that China's urbanisation rate will increase by nearly 1% per year during the next 15 to 20 years, which represents around 300 million people who will move from rural areas into cities (China Daily, 2009). Today, China's average population density is Page | 36 approximately 138 per km2 (Wikipedia, 2009b), but with extreme variations in rural population densities, ranging from less than one to more than 400 per km2. In stark contrast, the highest urban population density per km2 is 50 000 to 60 000 as in the case of central Beijing, Shanghai and Chongqing (China Daily, 2009).