LI Meina, YIN Ping, *, DUAN Xiaoyong, LIU Jinqing, 3), QIU Jiandong, and PHUNG Van Phach



Land-Use Changes and Human Driving in and Near the Yangtze River Delta from 1995–2015

LI Meina1), 2), YIN Ping1), 2), *, DUAN Xiaoyong1), 2), LIU Jinqing1), 2), 3), QIU Jiandong1), 2), and PHUNG Van Phach4)

1),,,266071,2),,266061,3),,266590,4),,

We analyzed the characteristics and trends of land-use change in and near the coastal zone of the Yangtze River Delta (YRD) during five periods (1995, 2000 2005, 2010, and 2015) using remotely sensed Landsat imagery. Using automatic supervised classification combined with visual interpretation, we obtained land-use information for five study areas (Nantong, Shanghai, Jiaxing, Ningbo, and Zhoushan). Significant land-use changes have occurred in this area between 1995 and 2015, characterized in particular by large reductions in cultivated land and rapid increases in urbanized land. In addition, land reclamation was very active in this period as an effective supplement to the increased demand for land development: since 1995, 1622km2of land was reclaimed from near-coastal regions in the study area. This increase in urbanization was jointly driven by population, economic, transportation, and policy factors. Urban areas expanded from the center outward in concentric rings, with infrastructure guiding the radial expansion of development along transportation corridors, thus forming a network of connections. Due to the influence of national land regulation policies, the expansion rate of development in the YRD gradually diminished after 2010. This indicates that the area’s resource and environmental carrying capacity has reached a saturation stage in which urbanization has transitioned from broad and incremental expansion to the intensive use of land resources.

land use; coastal zone; Yangtze River Delta; land-use change; remote sensing technology; reclamation; driving mechanisms

1 Introduction

Land use refers to human utilization, management, and transformation of land based on its physical and ecological characteristics and the needs of human societies including basic necessities, socioeconomic development, recreation, and so on (Pijanowski and Robinson, 2011; Bajocco., 2012; Pourebrahim., 2015; Zhao., 2017). The large-scale changes in land use caused by rapid urban expansion (human activities are most concentrated in cities) have been particularly significant (Li., 1995; Foley., 2005). At a macroscopic scale, these areas are constantly undergoing rapid development and changes (Zeijl and Fresco, 1997; Gao., 2006; Ma., 2008; Hao and Ren, 2009). Hence, monitoring and analy- zing urban spatial expansion and land-use changes are important for understanding modern urban development, management, and planning (Muttitanon, 2005; Liu.,2008; Hoover., 2017). Analyses of land-use change often focus on their mechanisms which can be used to predict the future change trends. At a 20 year time scale, with relatively stable natural factors and their cumulative effects, human activities generally constitute the dominant mechanisms driving land-use change (Ning., 2017; Tan., 2017). Ehrlich and Daily (1993) proposed that population, degree of enrichment, and technology are the most important forces driving human activities, while Rozanov. (1990) added income, political and economic status, and culture as further driving forces.

As human populations are often concentrated near coastlines, extensive research has been conducted in China and elsewhere on coastal land use changes (Yu., 2011; Ning., 2017; Tan., 2017). For example, the LaCoast project aims to provide scientific data on environmental indicators for the comprehensive management of European coastal zones by conducting detailed investigations of land cover changes (Bolstad and Lillesand, 1992; Lambin., 2002; Pal and Master, 2005; Inglada, 2007). The Coastal Change Analysis Program (C-CAP) involves the comprehensive application of aerial photographs and remotely-sensed data from Landsat TM, SPOT, HRV, and other satellite platforms to monitor the patterns of change in coastal wetlands and adjacent uplands in the U.S. (Ou- ma., 2008; Gong., 2013). In recent years, with the increasing urban development in coastal zones, significant transformations have occurred in land use of these regions, highlighting the tensions between coastal zone de- velopment and protection (Tian., 2003; Barney, 2004).

The Yangtze River Delta (YRD), where the Yangtze Ri- ver enters the East China Sea, is one of the largest river deltas in the world. It contains the most rapid social deve- lopment in China, as well as the highest degrees of land useand greatest extents of land-use change. As the most highlydeveloped coastal region in China, the YRD faces immense long-term pressure from population and economic growth, which is characterized by high development intensity, reduced land protection, high comprehensive output, high loss of cultivated land, and large changesin land type composition (Zheng., 2004; Liu., 2012). Therefore, examining land use changes in the coastal zones of the YRD is a crucial subject for scientific research.

In this study, we analyzed the characteristics and trends of land-use change in the Yangtze River Delta (YRD) from 1995 to 2015 with four five-year periods using remotely sensed Landsat imagery. Our results can serve as a scientific basis for planning decisions regarding the sustainable use of land resources and the environmental protection of coastal zones in China.

2 Study Area

The study area was located in the heart of the YRD, including five cities, Nantong, Shanghai, Jiaxing, Ningbo and Zhoushan, with a total land area of 29470km2(Fig.1). The YRD’s coastal zone has unique advantages in location with rapid and persistent socioeconomic development. With recent vigorous developments in the marine economy, Jiangsu and Zhejiang provinces and Shanghai have successively implemented long-term plans for marine economic development. Moreover, tidal flats and other coastal resources (., mineral, aquaculture, and freshwater resources) have been vigorously developed along with land reclamation, development of new coastal industries, and so on. These measures have substantially promoted the optimization and upgrading of industrial structure in the YRD coastal zone, and enhanced its overall economic strength. They play an invaluable role in the coordinated development of the central and western regions, improving the productivity distribution of national coastal zones and strengthening the exchange and cooperation of China with European, Northeast Asian, and Central Asian countries.

3 Data and Methods

3.1 Data Sources

We collected 5 years, 1995, 2000, 2005, 2010 and 2015 (Table 1), of image with the same months from the US Landsat (TM5TM7TM8) satellite. All data were processed by spectral band synthesis, geometric correction, and color stretching. In addition, we collected 1:150000 –1:300000 maritime charts of the YRD coastal zone as supplementary data. After digitization, the charts were used as an interpretation reference for the analysis of coastal reclamation.

Fig.1 Study area in the Yangtze River Delta.

Table 1 Information of the remote sensing data

3.2 Study Methods

Land-use change is an extremely complex process; past studies on land use have often involved the integration of sociology, economics, biology, geography, spatial information science, and multiple other disciplines. This study used geographic information systems methods including indoor space identification, geospatial information overlay, transition matrix analysis, and intensity index analysis, combined with spatial statistics, correlation analysis, and other methods of social statistics.

3.2.1 Supervised classification

First, using large-scale topographic maps, we determined the baseline accuracy of the 1995 image (average error did not exceed 30m), then corrected the subsequent years’ images to a unified projection coordinate using the corrected 1995 image. Drawing upon actual geographic features, national classification criteria, and satellite imagery, we divided the land-use types of the study area into five types: cultivated land, forest, grassland, water, and developed land.

We used supervised classification, also known as training classification. This common procedure uses known sample pixels as a means of identifying pixels from unknown categories and is generally divided into four processes: 1) define training samples; 2) perform supervisory classification; 3) evaluation classification results; and 4) post-processing. We used the maximum likelihood method with ENVI and ArcGIS 10.1 software.

3.2.2 Conversion matrix analysis

Conversion matrix analysis is a powerful tool used for the quantitative description of land use characteristics and the direction and structure of changes. The matrix is expressed in a tabular format, and reflects both the distribution of land use types at the start and end of the study period as well as the sources and composition of each land use type within the study period. We used ArcGIS to overlay the land use maps and ArcMap to compute the conversion area between the different land use types in order to obtain the spatial conversion matrix. The resulting matrix was analyzed in order to facilitate the further identification of the spatial characteristics and internal evolution patterns of land use changes.

3.2.3 Urban development intensity index identification

The ratio of the average annual area of developed land expansion to the total land area of a given region can be expressed as an intensity index, as determined by the following equation:

whereBis the intensity index of developed land expansion for region,Uis the area of developed land expansion for regionfrom the previous base year to the following base year,is the total land area of the region, andis the change in time in years.

4 Results and Discussion

4.1 Characteristics of Land Use Change

Fig.2 shows the land-use maps obtained through analysis of the 1995, 2000, 2005, 2010, and 2015 LandsatTM images of the study area. The relative proportion of indivi- dual land-use types collectively represented the land-use status of the region. From these results, we obtained the total area of each land-use type from each period, the relative percentages of these types, and other statistical values (Table 2).

In 1995, the land-use types in the YRD’s coastal zone were predominantly cultivated land, forest, and developed land. By 2015, although the predominant land use types remained unchanged, there were significant variations in their proportions: cultivated land decreased by 12.8%, while developed land increased by 13.4%, thus becoming a major land-use type.

Fig.2 Land use classification results within the Yangtze River Delta from 1995–2015 using Landsat imagery.

These results clearly show the rapid rate of urban expansion and concurrent substantial reductions in cultivated land within the YRD’s coastal zone.

Table 2 Percentage of each land use type within the study area for each year and total change by land area

4.2 Trends in Land Use Conversion

The statistical results indicate that many significant land-use changes occurred in the YRD from 1995–2015 (Table 3). First, significant changes occurred within non- developed land, mainly involving the reduction of cultivated land, conversion of forests to development, conversion of grassland to forest, and conversion of water to development. Second, developed land increased significantly, mainly involving conversion from cultivated land. In the 20 years from 1995 to 2015, the area of developed land within the study area increased from 2684.3km2to 6661.4km2, a total increase of 3977.1km2and an annual average increase of 198.9km2. Of this increase, 3532.1 km2was converted from cultivated land, accounting for 92% of the newly-added area. Thus, cultivated land is the main source of the increase in urban development, although other processes have led to lesser conversions am- ong all land-use types. The urbanization process is more obvious.

Table 3 Land use conversion matrix for the study area (km2)

4.3 Trends in Developed Land Expansion

Using the cities of Nantong, Shanghai, Jiaxing, Ningbo, and Zhoushan as the basic calculation units, the intensity index of developed land expansion for the YRD coastal zone was calculated according to Eq. (1). Relatively large intensity indices were calculated for Shanghai, Jiaxing, Ningbo, and Nantong, which are coastal cities with rapid economic development; the indices for the first three were larger than or close to 1 (Fig.3).

Fig.3 The intensity index of developed land expansion for the study area.

This partially reflects the effective land protection given by these regions to key infrastructure construction projects (Shi, 2012), which actively promoted their smooth construction. These projects were beneficial to the promotion of regional socioeconomic development and in the provision of socioeconomic services.

As shown in Table 4 and Fig.4, the expansion rate of developed land was greatest from 2000–2005, with sequentially lower values in 2005–2010 and 2010–2015. Thus, the spread of developed land has been effectively curbed, development intensity has been controlled, and developed land has transitioned from incremental ex- pansion to intensive use of land reserves.

Table 4 Changes in developed land area in different periods (km2)

Notes: A, Total expanded area (km2); B, Annual expanded area (km2)

4.4 Spatiotemporal Changes in Coastal Zone Reclamation

We also analyzed the land-use maps in order to assess the amount of land reclaimed by filling near-shore areas in each city (Table 5; Fig.5). The overall land reclamation activities within the study area showed a trend of rapid increase after 2005, with the most activity occurring in Shanghai.

Fig.4 Spatio-temporal mapping of developed land in the study area (1995–2015).

Table 5 Land area newly reclaimed from near-shore regions within the study area (km2)

4.5 Driving Mechanisms of Land Use Change

Although the driving factors of land use change include both natural and socioeconomic ones, we focused on the analysis of human driving mechanisms for land use change (using developed land as an example) with regards to transportation, development, economic growth, and policy regulation.

4.5.1 Population factors

We collected the 1995–2015 statistical yearbooks for the cities in the study area and performed linear correlation analysis between population growth and the increase in construction land area (Fig.6). In general, the correlation between these factors was very high, indicating that as the population grew, their demand for developed land increased as well.

In addition, there were significant differences among cities of different sizes. For example, megacities such as Shanghai had good linear correlation, whereas smaller cities did not show such significant correlation. We suggest that the primary reason for this was that large cities have higher population concentrations: the urban population in Shanghai increased from 14.14 million in 1995 to 24.15 million in 2015 with a strong demand for construction land. In comparison, small- and medium-sized cities have significantly lower population growth and rates of urban development: the urban population in Zhoushan increased from 0.98 million in 1995 to 1.146 million in 2015.

Fig.5 Temporal map of lands reclaimed from near-shore regions in the study area (1995–2015).

Fig.6 Correlation analysis of total population and developed land area in the study area.

4.5.2 Transportation construction

Transportation infrastructure can have strong guiding effects on the formation of land-use patterns, which can be significant in the expansion rate and directionality of land development. According to internal statistics, in 2009 the total mileage of roads in the YRD was 262400km and the total mileage of highways was 7821km, which increased by 0.77% and 5.21%, respectively, compared to the previous year. Therefore, the construction of transport trunk lines has become the backbone and framework of urban spatial expansion in the study area, with mutual and complementary influences between the two. Transportation development has accelerated the further expansion of developed areas, strengthened the connections between cities, and driven the development of real estate and commercial industries along the transport lines within all urban areas.

These factors have all contributed to the rapid changes in developed land, as shown by the correlation analysis of developed land and highway mileage in the study area from 1995–2015 (Fig.7). For cities of all sizes, construction of transport infrastructure was relatively complete and road transportation was highly developed. The differences in expansion due to transportation infrastructure were not significant among the various small- and medium-sized cities within the study area.

Fig.7 Correlation analysis of highway mileage and developed land area in the study area.

4.5.3 Economic growth

Rapid economic development is the most important direct driving force for urban spatial expansion and is also the main guiding force for land use changes. The YRD is at the forefront of Chinese economic reform; the urban GDP of the study area increased from CNY 402.1 billion in 1995 to CNY 4.3642 trillion in 2015 (Fig.8). This swift economic development promoted an increase in urbanization and provided strong financial guarantees for urban renewal and new development, while causing a reduction in cultivated land as discussed above. As shown in Fig.8, Shanghai’s GDP increased from 249 billion 900 million yuan in 1995 to 25123 billion yuan in 2015, the economic effects of the megacity Shanghai’s economic growth have led to strong demands for development, such that the area of developed land increased significantly with rapid economic development.

Fig.8 Correlation analysis between Gross Regional Pro- duct and developed land.

4.5.4 Policy regulation

Land uses are formed within a specific policy environment, such that policy factors play an important role in producing land use changes. In the early stages of the Chinese economic reform, three cities in the YRD (Shanghai, Ningbo and Nantong), were the first batch of coastal port cities opened for trade, and hence enjoyed certain preferential policies in their economic development. In the 1990s, the 14th National Congress of the Communist Party of China formulated the major policies for the development and opening up of Shanghai’s Pudong District to drive the economy of the YRD and the entire Yangtze River Basin. This placed Shanghai’s economy in the fast lane, while the economy of the entire YRD region entered an unprecedented stage of rapid development. In the early 21st century, China established the Shanghai International Finance and Trade Center to achieve a new leap in the economic development of the YRD and Yangtze River Basin, leading to further preferential policies being promoted. In recent years, in order to establish an important gateway to the Asia-Pacific region, and to build a world- class urban agglomeration, China once again announced the relevant preferential policies in May 2010. These policies promoted the use of Shanghai as the center of development to enhance the internationalization of cities such as Nanjing, Suzhou, Wuxi, Hangzhou, and Ningbo, to encourage new urbanization, and to accelerate the process of modernization and integration.

5 Conclusions

1) Over the past 20 years, significant land use changes have occurred in the YRD coastal zone, characterized by rapid increases in developed land and large reductions in cultivated land, the latter accounting for 92% of the total area converted to development. The index of developed land expansion was higher in the northeast than the south- west. The annual expansion rate of urban development showed a gradually decreasing trend after 2010. This indicates that the resource and environmental carrying capacity of the YRD coastal zone has reached a stage of saturation, the spread of development has been effectively curbed, and development intensity has been significantly controlled.

2) To supplement available land resources, the intensity of land reclamation within the YRD coastal zone is high, with 1622km2of land area newly added from 1995–2015. The most active reclamation period was 2010–2015, with 557.3km2of reclaimed land (34.3% of the total reclaimed land). These observations reflect the rapid land expansion, higher demand for land reserves.and greater development needs of this period.

3) Our analysis of the population, economy, transportation facilities, and related policies from 1995–2015 in the coastal zone of the Yangtze River Delta found that the increase of coastal population, GDP, and transportation facilities greatly stimulates the expansion of developed land. In other words, the changes in land use here were based on natural and geographical attributes but guided and restrained by policy. At the same time, an increasing amount of human behavior is being driven by anthropogenic factors such as population and socio-economic variables, producing complicated changes.

Acknowledgements

This study was supported by China-ASEAN maritime cooperation fund: Comparative Study of Holocene Sedimentary Evolution of the Yangtze River Delta and the Red River Delta, the Natural Science Foundation of Shandong Province, China (No. ZR2014DQ020), China Geological Survey Project (No. DD20160145), and the National Na- tural Science Foundation of China (Nos. 41706074 and 41506107). We also want to thank the editor and the reviewers.

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. E-mail: pingyin@fio.org.cn

(Edited by Chen Wenwen)