Environmental Science & Technology nearly 21%, its proportion in China’s GDP ∼5 times to 3.8%. The income from land leases can account for 30 70% of a city’s financial revenue.35 This income of government has a designated use, with 50% tied to improvement of the leased land such as providing basic infrastructure including water, electricity, Inter- net, wastewater treatment, gas, roads and heating. The remaining 50% goes to infrastructure investment within the city.50 These investments directly create jobs in the construction sector, which attracts more people into cities and thus stimulates further urbanization. A better urban infrastructure, in turn, attracts further investment in industries and thus contributes to the economic growth of the city and the region in the long run. Therefore, land acquisition has been used heavily by Chinese local governments to fuel urban development and finance infrastructure provision.51 Under this circumstance, land plays an active and significant role in economic growth in China. Policy Implications for China. Our results have significant policy implications for China, revealing a tension between urbanization, environment and economic growth. Landscape urbanization brings economic growth, but at the same time could cause negative environmental impacts52 leading to serious environmental problems in some Chinese cities.53 On the one hand, our results confirm that the national policy of promoting urbanization to enhance economic growth does hit the mark. Since by definition built-up area expansion requires infrastruc- ture investment, our results might highlight the importance of infrastructure investment for urbanization to deliver the antici- pated economic growth. On the other hand, the positive feedback suggests that China’s policy to arrest the loss of agricultural land might be challenged by its own policy to promote economic growth through urbanization. Urbanization takes up large amounts of arable land which presents a major threat for sustainable agricultural production and food security in China.43 In 2006, China had 0.09 ha of arable land per capita, which was less than 40% of global average; meanwhile it lost 0.31 million hectares of arable land, of which 84% was changed into construction land.54 At this rate of urban expansion, the government designated food security “bottom line” of 120 million hectares of arable land,55 is fast approaching. The close linkages between urban expansion and economic growth indicate that the current economic growth model in urban China is highly dependent on natural resource input, in this case, land. It is likely that eventually this resource-intensive growth mode will change toward a more service-oriented one and thus require less land input, as experienced in other devel- oped countries. However, it might be very diﬃcult for China to control urban expansion without sacriﬁcing economic growth, at least under its current economic growth model. While the result only reﬂects the tendency on an aggregated level and therefore does not dictate the behavior of each and every individual city should follow the same pattern, empirical evidence does seem to reinforce our ﬁndings. For example, nearly half of the ﬁrst designated greenbelt in Beijing was already changed into built- up area in 2005,56 suggesting a strong tendency of urban land-use expansion and the diﬃculty of preventing it. Empirical evidence in the macro-economic history of China also supports the close linkages between urban expansion and economic growth. In 1999, the Chinese government strived to keep the economic growth rate at 8% after the economic recession caused by the Southeast Asia ﬁnancial crisis, and found that urbanization was a good instrument for promoting economic growth.57 In 2004, the POLICY ANALYSIS State Council subsequently decided to tighten its control over permission for new land development, which has brought about an economic slowdown in some cities and regions.58 This challenge is likely to continue into the future. As part of its economic growth strategy, the Chinese government aims to increase demographic urbanization from 43% in 2005 to 47% by 2010, with an economic growth rate of 7.5%.55 This will inevitably increase demand for built-up areas for infrastructure, industry, and residential use. Given the agricultural land scarcity in the country, there is an urgent need for China to identify an alternative pathway that eases the heavy dependent on land resource input. While it is not clear to what extent the causal eﬀect between urban expansion and economic growth is applicable to other contexts than China, putting urban expansion under control is a universally challenging task.59 For example, the greenbelt in Seoul aimed at containing expansion within its ring resulted in leapfrog development.60 Bad urban planning or poor implemen- tation of such is often blamed for uncontrolled urban growth. Assuming the existence of a feedback between urban expansion and economic growth is a widespread phenomenon, then the driving force is coming from a diﬀerent dimension and urban planning alone might not be suﬃcient to achieve the goal. Implications for Urban Research. Our findings imply that compared to a demographic urbanization indicator, a landscape indicator has the potential to better reveal the complex linkages between urbanization and accompanying economic and envi- ronmental processes. Built-up area expansion is a spatial mani- festation of population, economic, and environmental dynamics of urbanization. As discussed by Bloom et al., there are diffe- rent types of urbanization in terms of drivers and economic outcomes,5 among which demographic indicators alone cannot distinguish. Built-up area might differentiate them to some extent. While urban population growth with built-up area expan- sion might indicate a direct association with economic activities, urban population growth without built-up area expansion might indicate urbanization without economic growth, especially in low-income countries. In addition to economic aspects, built-up area also reveals strong environmental linkages through concen- tration of materials,61 and varying energy use and GHG emis- sions according to different urban density and transportation system.62,63 Our analysis on urban growth pattern shows larger cities gain more per capita GDP growth, and more and faster in terms of total GDP, which endorses Betterncourt et al.’s44 result. It also shows that richer and larger cities (both in terms of population size and built-up area) are expanding more. These suggest the relationship between city size and wealth creation is not only nonlinear but also bidirectional and complex, which in turn suggests the existence of feedback mechanisms in the growth of cities. The positive feedback between landscape urbanization process and economic growth identiﬁed in this study may reveal partly the complex mechanism of such nonlinear, accelerated growth in city size and wealth. Urban land expansion is not only the consequences of economic growth in cities, but also drivers of such growth. While it seems urban land expansion can trigger such feedback within the Chinese contexts, there might be other types of such positive feedback in work in other context, involving other factors. Uncovering these dynamics and mecha- nisms of the interaction among diﬀerent components within an urban system is an important step toward understanding the complexity of cities and urbanization processes. This will in turn 137 dx.doi.org/10.1021/es202329f |Environ. Sci. Technol. 2012, 46, 132–139