The suitable construction lands (SCL) in YRD were classified into six categories including grassland, woodland, gardenland, swamp, urban land and others. The area is 55,851.10 km^{2}, accounting for 48.62% of the total area. Among which, the construction land area reached 24,951.21 km^{2} in 2008, accounting for 21.72% of the total YRD and 44.67% of the SCL.
3.2.1 Scenario analysis of construction land potential
The area of non-restricted area (a), low restricted area (b), medium restricted area (c), relatively high restricted area (d) and high restricted area (e) is 84,637.72 km^{2}, 5280.31 km^{2}, 9524.89 km^{2}, 3278.84 km^{2} and 12,126.58 km^{2} respectively. The above types of lands account for about 73.68%, 4.60%, 8.29%, 2.85% and 10.56% of the YRD. Based on a, b, c, d and e restricted areas, this paper divided the potential of construction land in the YRD into four scenarios of CLP I, CLP II, CLP III and CLP IV. According to the size of CLP area of every county, they are all classified into seven criterions: 0, 0-100 km^{2}, 100-200 km^{2}, 200-300 km^{2}, 300-400 km^{2}, 400-500 km^{2}, 500-1000 km^{2}, and above 1000 km^{2}. Meanwhile, measured by CLP percentage in county area, CLPI, CLPII, CLPIII and CLPIV are divided into seven criterions: 0, 0-10%, 10%-20%, 20%-30%, 30%-40%, 40%-50%, and 50%-100%. In terms of the number of counties in different criterions, the higher the quality of CLP is, the smaller the area of CLP and the percentage in county area are. The proportions show the area of CLP I and CLP III is larger than that of CLP IV and CLP II. And there exists significant regional imbalance in YRD CLP.
CLP I has the largest area and maximum size of potential construction lands and it is defined as the study area minus the high restricted area in this paper. The area of CLP I is 30,899.90 km^{2}, which accounts for 26.90% and 55.33% of YRD and SCL respectively. The average CLP of county and city is 339.56 km^{2} and 1931.24 km^{2} respectively, but 14 counties have no CLP, which are distributed mainly in Nanjing, Yangzhou and coastal area of Jiangsu.
CLP II equals the total area minus high and relative high restricted area. The area reaches 28,089.24 km^{2} which takes 24.45% and 50.29% of the YRD and SCL respectively. The average CLP of counties is 308.67 km^{2}, meanwhile the average CLP of cities is 1726.32 km^{2}, all of which is less than that of CLP I. There are 20 counties without CLP, and distributed mainly in Yangtze riverside area, coastal area and the eastern plain to the Taihu Lake.
CLP III refers to the total area except the high, relatively high and medium restricted area. The area is 19,037.36 km^{2} which takes 16.57% and 34.09% of the YRD and SCL respectively. The average CLP of 91 study units at county level is 227.77 km^{2} which is 80.90 km^{2} smaller than CLP II, moreover which of the cities is 1189.84 km^{2} which is 546.39 km^{2} smaller than CLP II. The number of units without CLP increases too, and there are 4 cities of Suzhou, Taizhou, Zhenjiang and Yangzhou, and 29 counties without CLP, with a range being expanded to central Jiangsu and north of Zhejiang.
CLP IV only includes the non-restricted area and represents the least area and highest quality of potential construction lands. The area is 15,710.81 km
^{2}, which accounts for 13.68% and 28.13% of the YRD and SCL, respectively. The average CLP of counties is 227.77 km
^{2} which is 110.89 km
^{2} smaller than that of CLP III, and which of the cities is 879.28 km
^{2} which is 310.56 km
^{2} smaller than CLP III. Besides Suzhou, Taizhou, Zhenjiang and Yangzhou, two more cities (Huai’an and Jiaxing) and 31 counties have no CLP, and the range of the area without CLP have expanded to northern Jiangsu and Zhejiang. The city with largest CLP changing from Hangzhou to Ningbo represents that the CLP III takes great proportion of SCL (
Table 3 and
Figure 3).
3.2.2 Construction land potential of YRD
According to equation (6), the potential construction land in YRD is 24,989.65 km
^{2} which accounts for 21.76% and 44.74% of the total YRD and SCL (
Figure 3 and
Table 3).
Based on the result of county level research, the average CLP is 274.61 km^{2}, and there are 26 counties without CLP. The number of counties with CLP 0-300 km^{2}, 300-500 km^{2}, 500-1000 km^{2}, and above 1000 km^{2} are 40, 10, 9, and 6 respectively. For each of the four CLP intervals above, the proportions to the YRD is 22.11%, 15.76%, 24.75%, and 38.43%. The average CLP proportion of the counties is 17.30%. Besides the 26 counties without CLP, the number of counties at 0-10%, 10%-20%, 20%-30%, 30%-40%, 40%-50% and >50% intervals is 14, 21, 10, 6, 5 and 9, respectively, and 43.96% of the counties have CLP proportion lower than 10%, meanwhile 67.03% of the counties lower than 20% and only 9.89% larger than 50%.
On the cities level, the average CLP of cities is 1561.85 km^{2}. There are 5 cities with CLP less than 500 km^{2}, 6 cities’ CLP between 500 and 1000 km^{2} and 5 cities’ CLP above1000 km^{2}. Each interval accounts for 3.77%, 17.21%, 24.75%, and 79.02% of the YRD. Hangzhou, Ningbo and Shaoxing take up 65.75% of the CLP in the YRD. This shows great space unbalance. Sixteen cities’ average CLP proportion reaches 16.55% with Hangzhou shares the largest percentage of 48.61%. There are 4 cities’ proportions larger than 30%, 9 less than 10%, and 12 less than 20%. Cities which have less than 10% of CLP value account for 56.25% of the number of the YRD cities.
According to the research at the province level, 10 cities in Jiangsu take up about 21.25% of the CLP in the YRD, the average CLP proportion is 7.81%. There are 5 cities in Zhejiang that account for 67.26% of the CLP in the YRD and the average cities area proportion is 35.04%. Shanghai takes 11.22% of CLP and the average cities percentage is 11.64%. Based on the proportions above, most of the potential construction lands are located in Zhejiang.
Table 2 The characteristics of construction land potential in different scenarios |
Figure 3 The construction land potential of various zonings of the Yangtze River Delta |
3.2.3 Spatial pattern of construction land potential
The spatial pattern of YRD’s existing construction land intensity has been formed by YRD’s physical geography and China’s long-term regional development policies. The spatial pattern of the CLP in the YRD has the following features: Firstly, there exists significant regional imbalance in the YRD’s CLP. On the one hand, the CLP space is unevenly distributed. Zhejiang and Jiangsu is the main body of south and north YRD respectively. According to the proportion of CLP, south YRD’s CLP is much larger than north YRD. On the other hand, the CLP space is also imbalance in the administrative level. Regional central cities are seriously lack of CLP. Based on the study result, taking regional center cities as the main body of the region, there are 66 counties with CLP less than 500 km^{2} and the area of CLP only accounting for 22.11% of YRD CLP. Secondly, CLP in all the prefecture-level cities and Shanghai only takes 15.05% of YRD CLP. Thirdly, the potential construction land in YRD presents circle layered spatial pattern that gradually increasing from the core of prefecture-level cities to outlying regions. Fourthly, based on CLP I-CLP II-CLP III-CLP IV, with the quality upgrade of CLP, low potential region expands from north to south while the high potential region narrowing down correspondingly to the south area. Fifthly, the region without CLP of YRD has formed a “Y-shaped” spatial distribution pattern.
The reasons for the forming of the spatial pattern is mainly due to the following:
First, the terrain of north YRD is more flat than south YRD and the north YRD is the fluvial plain of the Yellow River. Huaihe River and Yangtze River basins (especially the flatlands and coastal areas) are the most suitable regions for human residences. Second, since 1978 south Jiangsu (Sunan) has the foundation and tradition of engaging in collective economic development. This region has formed an endogenous growth model of “Sunan pattern” encouraging township enterprises development in order to stimulate industrialization. “Sunan pattern” promoted the expansion of local construction land. Third, the radiation of Shanghai and excellent transportation condition also accelerates the rapid development of south Jiangsu. Fourth, Wenzhou (Zhejiang) pattern in south YRD is completely different from “Sunan pattern”. Wenzhou pattern adopts exogenous growth model that relies on family industry and external professional market development and this kind of growth pattern makes little contribution to the increase of construction land.
County-level research shows that the CLP per capita of YRD is 0.045 ha/person. This is 0.021 ha/person larger than national average construction potential (
Xu et al. 2011). There are 26 counties with zero CLP in Jiangsu and most of them are located in south Jiangsu, including 10 districts directly under cities and 16 counties. There are 45 counties with average CLP less than 0.05 ha/person, 9 counties between 0.05 and 0.1 ha/person and 10 counties in Zhejiang between 0.1 and 0.3 ha/person. The largest average CLP is 1.71 ha/person in Chun’an county. From this point of view, 28.57% of the counties in YRD, which account for 23.04% of the YRD, already have zero CLP. Some 58.24% of the units’ average CLP is below the national average and these units take 50.27% of the total YRD. Furthermore, 75.82% of the counties’ average CLP is below the YRD average level and takes 67.13% of the YRD. Therefore, the average CLP of counties is unevenly distributed and there are less than 25% of the counties (mainly in Zhejiang, except Wujin, Lishui and Jintan city) reaching the average CLP in the YRD.
With regard to the prefecture city, the average CLP per capita of 16 prefecture cities is 0.043 ha/person and Hangzhou has the largest value of 0.25 ha/person, Taizhou has the smallest value of 0.002 ha/person. There are 12 cities with average CLP per capita values less than 0.05 ha/person, and the values of Taizhou, Yangzhou, Jiaxing, Nantong and Zhenjiang are less than 0.01 ha/person each. Seven cities’ (Shanghai, Suzhou, Yancheng, Huaian, Wuxi, Nanjing and Changzhou) CLP per capita values are between 0.01 and 0.03 ha/person. CLP per capita values are more than 0.05 ha/person in Shaoxing (0.08), Ningbo (0.09), Huzhou (1.11), and Hangzhou (0.25), and 80% of the cities in YRD have CLP per capita less than 0.03 ha/person and only 2 cities’ average CLP are more than 0.1 ha/person. The average CLP of 16 district cities is 1.37 times of current area per capita. Among the 16 cities, the average CLP of 9 cities (Taizhou, Yangzhou, Jiaxing, Suzhou, Zhenjiang, Shanghai, Yancheng, Wuxi and Huai’an) is less than 62% of current area per capita. Other 7 cities’ average CLP is more than twice as large as current area per capita value. Hangzhou has the largest CLP, which is 8.06 times of current area per capita value. CLP values of Ningbo, Shaoxing and Huzhou are between two and three times larger than current area per capita. Thus, the CLP per capita values vary a lot among different cities and are unevenly distributed in south and north area in YRD.
From the research of province level, 10 cities in Jiangsu have average CLP per capita of 0.014 ha/person which is less than the national and YRD average CLP value. Eight cities’ CLP per capita are below the national average level except Nanjing and Changzhou. CLP per capita in Shanghai is 0.01 ha/person which is smaller than Jiangsu. The average CLP per capita of 5 cities in Zhejiang is 0.106 ha/person and this is higher than both the national and YRD average CLP level. From the above number, Zhejiang has the highest potential construction land compared with Jiangsu plate and Shanghai (
Figure 4).
Figure 4 The construction land potential per capita of various zonings of YRD |