3.1. Evaluation and Planning of Ecological Land Use at City (Macro) Scale
Figure 3 shows the land use of Shanghai (macroscale) in 2018.
Table 7 is the land utilization situation of Shanghai in four different years (1990, 2000, 2010, 2018), and
Table 8 is the proportion matrix of land-use transfer in Shanghai from 1990 to 2018. In 2018, the main land-use types of Shanghai were cultivated lands and construction lands, which account for over 90% of the total area. The cultivated area is mainly distributed in the south of the city and Chongming Island. During the period of 1990–2000, arable area decreased by 8.5% and grassland decreased by 60.1%. The constructive area increased significantly, with an increasing rate of 38.7%. From the land transfer matrix, the lost arable land was mostly transferred into constructive area, while 18.9% of the grassland was transferred into constructive area. The matrix also shows that 44% of the grassland was transferred into the water area. During the period of 2000–2010, the constructive areas increased rapidly with a rate of 58.1%. In the meantime, the arable area decreased substantially by 18.6%, and the decreased area was mostly changed into the constructive area. Other types of land (expect unused land) were transferred into constructive areas in different degrees. During the period of 2010–2018, the constructive area still increased with a relatively smaller rate of 21.4%. In this period, grassland increased unprecedentedly with a rate of 506%. The water area and unused land increased as well. Meanwhile, the transfer rates between different types of lands slowed down. In this period, the arable area still was the main source of constructive land and ~14% of the arable area, along with 7.3% of water area, 9.6% of forest land and 25.1% of grassland, changed into constructive land.
From 1990 to 2018, the areas of arable land and forest land decreased by 35.9% and 18.8%, respectively. Constructive area, grassland, water area, and unused land increased by 166.3%, 115.1%, 9.3%, and 72%, respectively. In this period, 35% of arable area, 20% of forest land, and 40% of grassland have been transferred into constructive areas, which results in the continuous increase of constructive area in about 30 years.
In the spatial distribution of carbon sequestration (
Figure 4), southern Shanghai and Chongming Island have better ability of carbon sequestration, while the downtown and its surrounding area have lower carbon sequestration. With the expansion of the urban areas, the low carbon sequestration area spreads from 1990 to 2018. All the districts of Shanghai show an overall decrease in carbon sequestration (
Table 9). During the period, Chongming Island, Pudong District, and Fengxian District have higher carbon sequestration, with average carbon sequestrations of 11.39 Tg, 9.17 Tg, and 6.26 Tg. The downtown area has the lowest carbon sequestration of all years, with an average of 0.4 T. For the carbon sequestration per area, Chongming Island, Fengxian District, and Qingpu District have the highest values, which are 9.05 t/km
2, 6.94 t/km
2, and 6.8 t/km
2 respectively. The downtown area still has the lowest carbon sequestration per area, with a value of 1.25 t/km
2.
The correlations between the carbon sequestration and different land types in Shanghai in four different years are shown in
Table 10. As seen in the table, lands with high carbon density, such as arable land and forest land, have significant high correlations with carbon sequestrations. Arable land and forest land are the areas with high carbon density, which slow down the losing rate of carbon sequestration in Shanghai. Though grassland has high carbon density, the area of grassland is too small to influence the carbon sequestration in the ecosystem. The constructive area has significant negative correlations with carbon sequestration in the period (−0.822, −0.915, −0.556, −0.911). The increasing area of constructive land in Shanghai leads to loss of carbon sequestration directly.
In the urbanization progress of Shanghai, the area of ecosystem is shrinking continuously, which compromises the carbon sequestration ability of Shanghai. The loss of carbon sequestration in Shanghai is contributed to expansion of constructive land and compromise of arable land. Also, due to the strict farmland protection regulations, the compensation of arable land is from forest land and grassland, which also leads to the reduction of the carbon sequestration level of the ecosystem.
The habitat quality results of four years are shown in
Figure 5, and the detailed habitat qualities of each district in Shanghai are shown in
Table 11. Habitat quality ranges from 0 to 1, and the values closer to 1 show the better habitat quality of the areas. The better habitat quality indicates that the city has a relatively complete ecosystem, which can maintain the biodiversity of the area. The average habitat quality of Shanghai in 2018 is 0.35, which is the lowest value from 1990. Habitat qualities of different districts in Shanghai in four different years are shown in
Table 11 and habitat qualities of different land types are shown in
Table 12. The downtown area has the worst habitat quality and the area expands through the years. In the year of 1990, Qingpu District, Chongming Island, Fengxian District, and Jinshan District were the four district areas having the highest habitat quality values. With the development of the city, Chongming Island, Qingpu District, and Jinshan District are the three districts with the highest habitat qualities in the year of 2018. The results also indicate that Chongming Island is the least influenced district in Shanghai, while Minhang District is the most influenced district by the urbanization.
In nearly 30 years, the massive-scale human activities in Shanghai had led to an increase in land-use intensity and weakened the quality of the ecological environment in Shanghai. Especially, in the downtown area, the population density and construction density are much higher than other districts of Shanghai, which leads to the declining quality of the ecosystem.
The water conservation index (indicator) is mainly measured by precipitation interception, runoff regulation, evapotranspiration, water purification, etc. The results of water conservation are listed in
Table 13 and shown in
Figure 6. From
Table 13, water conservation in all districts of Shanghai shows an overall decreasing trend from 1990 to 2018 and in 2018, Shanghai has a water yield of 7.54 × 10
8 t. The average water depth decreases 22.52 mm and Baoshan District has the largest decrease in water depth, which is 62.79 mm. Meanwhile, Chongming Island lost 8.9 mm in water depth during ~30 years, which indicates its important role in maintaining the water conservation service in Shanghai. By the end of 2018, the districts with water depths over 120 mm are only Jinshan District, Fengxian District, Qingpu District, Songjiang District, and Chongming Island. From the spatial distribution (
Figure 6), the water conservation index decreases gradually from north to south. Jinshan District, Qingpu District, Songjiang District, Fengxian District, and Chongming Island have larger water conservation indexes.
The water conservation services of different land types change due to human activities. Therefore, water conservation services of different lands in Shanghai in the last three decades are calculated and listed in
Table 14. As seen in the table, forest land is the one with the highest water depth per area (276.76 mm). Grassland comes second, and arable land comes third, with 226.82 mm and 166.84 mm water depth, respectively. The loss of ecological land (forest land, grassland, etc.) is the main reason for the decreasing water conservation service. The correlations between land types and water conservation service indexes are listed in
Table 15. The table shows that forest land and grassland have significant positive correlations with water conservation during the period and the primary reason is that the plant layer can effectively intercept precipitation, increasing moisture in the soil and promoting the ability of water conservation. The reason for the low correlation between constructed land and water conservation service is that construction land destroys the structure of soil and the compaction and crusting of soil make the water content in soil decrease continuously. Overall, the changes in land-use influence the water capacity of the underlying surface and then influence the water conservation service in the city. If the worsening of water conservation services continues, the water cycle in nature would change and endanger the security of ecosystem in Shanghai.
The soil erosion in Shanghai was analyzed and
Figure 7 is the spatial distribution of soil erosion modules. As shown in the figure, the downtown area and its surrounding area have a less amount of soil erosion, while the south of the city has a large amount of soil erosion. The area with less soil erosion expands through the period.
Table 16 lists the soil erosion amounts of all the districts in Shanghai. The total amount of soil erosion of Shanghai reduced from 1120.63 × 10
4 t to 743.17 × 10
4 t, which indicates that the soil maintenance improved during this period.
Table 17 shows the soil erosion amount of different types of lands. From 1990 to 2018, arable land provided ~95% of soil erosion, while forest provided the least soil erosion. The lost area of the arable area might contribute to the decreasing trend of soil erosion in the study period. Also, the districts with larger areas of arable lands, such as Chongming Island, Pudong District, and Fengxian District, have larger annual soil erosion amount. The arable land provides food to the local community, and converting farmlands into forests in the premise that food is sufficient for the community is suggested.
Based on the four indicators above, the indicators of 2018 are chosen and normalizations of these four indicators are made to determine the importance level of the ecosystem services in Shanghai (
Figure 8). The normalization results are divided into four ranks in Shanghai (extremely important, important, generally important, and unimportant) and the results are shown in
Figure 9. The important and unimportant ecological land covers over 80% of the area in Shanghai, while extremely important ecological land covers less than 4% of the total area.
According to the importance level of ecosystem services, it can be seen that the ecological services of Shanghai present a typical circle pattern, with the main urban area as the center and the importance level upgrades through the center downtown area to the outside area. Based on this feature and the current situation of Shanghai, the city area is roughly divided into four main functional areas as shown in
Figure 10 (ecological bottom line area, ecological coordination area, ecological conservation area, and center construction area). The center construction area is the main construction area of the city, which is unimportant ecological land. This area is mostly used for commercial purposes (such as commerce centers, office buildings, and residential quarters) and lacks enough green space for local residents (lower than per capita public green area as reported in the government report of the eleventh five-year plan). The ecological coordination area is usually the boundary area surrounding the center construction area, which is mainly used as a coordination area for recreation and leisure for residents and ecological protection (such as emergency evacuation and flood diversion). The ecological conservation area is the basic ecological space of Shanghai and plays an important role in water and soil conservation, flood regulation and storage, wind and typhoon resistance, and habitat maintenance. Human activities, such as construction activities for commercial purpose, should be limited in an ecological conservation area to protect its ecological functions. The ecological bottom line area is an extremely important area of the ecosystem. This area has a significant role in an ecosystem. The area provides services such as water supply and biodiversity protection. Therefore, the ecological bottom line area should be protected.
3.2. Evaluation and Planning of Ecological Land Use at the Town (Meso) Scale
In the mesoscale study of ecological land use, towns with the areas of 50~200 km
2 are usually chosen. In this paper, Liantang Town was chosen in the mesoscale study. As shown in
Figure 11a, the macroscale ecological land-use planning plays a guiding role in mesoscale, including the division of the main functional areas and the implementation of overall control indicators. In the main function division at the macroscale, it can be seen that most of the area of Liantang Town is defined as the ecological conservation area, while a small part of the town in the east is defined as the ecological bottom line area, which is located in the upstream water source protection area of Huangpu River. In
Figure 11b, most of the area of Liantang Town belongs to important ecological land. A small proportion of the town area belongs to extremely important land, which is also mainly in the drinking water source protection area. The construction land of the town belongs to the unimportant ecological land.
The current land use of Liantang Town is shown in
Figure 12. The main land use of the town is arable land, construction land, and water area, which accounts for 68% of the total area. The arable area covers ~40% of the town. The construction land covers only 18% of the total area. The water area covers 21% of the area, which is relatively large. To evaluate the ecological services of Liantang Town, four indicators are selected, including water production capacity, habitat quality, carbon sequestration capacity, and grain production capacity. The results are shown in
Figure 13.
The water production service of Liantang Town (
Figure 13a) displays obvious regional differences. The nonecological area has high water production capacity, because precipitation can easily turn into a runoff on the impervious layer. Forest land has low water production capacity because of low water yield and rainfall interception. The water area also has low water production capacity because of the high evaporation. Also, the water area can effectively contain the water source, which can control floods and resist droughts.
The habitat quality of Liantang Town is shown in
Figure 13b. The value of habitat quality indicates the habitat’s ability to resist the influence of stresses. As seen in the figure, the nonecological land has relatively low habitat quality, as the area is highly influenced by human activities. Water area and forest land in Liantang Town have relatively higher habitat qualities because those areas are less influenced by human activities.
As shown in
Figure 13c, the ecological land with the best carbon sequestration service is forest land, which provides more than 60% of carbon sequestration in less than 10% of the area of Liantang Town. Grassland also has good carbon sequestration service, while arable land has the lowest carbon sequestration ability. The land in Liantang Town is mainly arable land, which limits the carbon sequestration capacity.
The land with the highest grain yield in Liantang Town is arable land, followed by the water area. Notably, the water area provides 17% of the grain yield, which is related to the large water area and large amounts of fish ponds. According to the evaluation and analysis of grain production capacity, Liantang Town is a typical agricultural production town, along with the aquaculture industry.(
Table 18)
On the basis of the evaluation and analysis, four indicators were normalized and divided into four levels of importance (
Figure 14 and
Figure 15), which are extremely important (0.85~1), important (0.75~0.85), generally important (0.65~0.75), and unimportant (0~0.65). The result shows that the ecosystem services of Liantang Town are mainly extremely important and important, which accounts for 57% of the total area, while generally important area accounts for 24% of the total area. The generally important and unimportant areas are located in the constructed area and its surroundings. After comparing the importance level of macroscale and mesoscale, the importance level areas mostly match. In macroscale, Liantang Town is mainly classified into extremely important and important ecological land as well. The further detailed importance division lists the generally important and unimportant ecological land for further management.
3.3. Planning and Implementation of Ecological Land Use at a Community (Micro) Scale
At the microscale, Changtian Community was selected as the research area. In this scale, field surveys and interviews with residents were carried out to obtain development wishes and planning requirements of residents. The layout of microscale land planning involves the interests of the public, which often determine the future direction of the social and economic development of the community. However, there are some uncertainties in the development goals of the communities. Therefore, multiple schemes/scenarios need to be compared to determine a relatively better practical scheme. Four schemes of different development goals and public demands are designed.
The first scheme (
Figure 16c) is an environmental improvement plan, which is aiming to renovate the ecological environment and build a clean community. According to the requirements of Shanghai environment improvement for rural areas, the environmental improvement plan is carried out with the purpose of beautifying the community environment and improving the living condition. According to this, this environmental improvement scheme contains five aspects of the key design: reduce the illegal construction land occupation and clear the main homestead area; regulate the waterfront ecological space and clear the riverside; widen the road in front of residence, reduce unnecessary hardened grounds and increase the green space; transfer the waste construction land into ecological land; keep the cultivated land, garden, forest land, and maintain their original layout.
The second scheme (
Figure 16b) is a farmland protection plan, which is mainly to improve agricultural function and protect cultivated land strictly. According to the requirements of macro and meso ecological land-use planning, Liantang Town bears great pressure on the farmland protection. Therefore, the main design principle is to protect basic farmland and increase the proportion of cultivated land area. The scheme contains four aspects of the key design: turn the current idle land into cultivated land to increase the ratio of cultivated land; turn the idle fish ponds into cultivated land or paddy field; carry out the high-standard farmland transformation to improve the farmland cultivation; carry out the basic comprehensive improvement of community environment to improve the living standard of residents.
The third scheme (
Figure 16d) is the ecotourism plan, which aims to optimize the ecological environment and develop rural tourism. Liantang Town is famous for its red tourism and rural tourism. Changtian Community is close to the urban centralized construction area and has the location advantage for the development of rural tourism. In the process of investigation, it is found that local residents also have the demand for developing rural tourism and the economy. The main design methods are as follows: renovate the natural rivers in the north and east, construct the waterfront leisure green space and form the waterfront ecotourism footpath; utilize the existing fish ponds, change the shape of them for tourism and sightseeing; adjust part of the cultivated land into orchards, increase the planting area of fruit forest, flowers and other crops, such as pear tree, peach tree, etc., and carry out picking events; optimize community public green space, improve the community’s infrastructure supporting, and improve the residential environment to development homestay economy. Through the above designs, the ecosystem, tourism, and economics are integrated to achieve the development of a community economy on the basis of not damaging the natural environment.
To compare the present layout and three schemes, the land uses of different situations are calculated and listed in
Table 19. The present land use of the Changtian Community is mainly cultivated land and water area, which account for 60% of the total area of the community. The environmental improvement plan aims to protect the environment and increase the area of arbor forest, avenue, grassland, and community park. The main purpose of the farmland protection plan is to improve the production capacity of agricultural products by increasing the area of arable land and improving grain productivity. The ecotourism plan is mainly to increase the main area of community parks, orchards and flowers, and emphasize the value of ecosystem services for sightseeing and entertainment.
To solicit opinions from local residents and managers, questionnaires were developed and distributed. The questionnaire results show that residents support ecotourism plan > environmental improvement plan > farmland protection plan. The residents suggested two aspects for future development: improve the living environment and basic service facilities of the community; improve the tourism industry in the future.
The results from managers are different and they support the environmental improvement plan > farmland protection plan > ecotourism plan. There are five suggestions proposed. Firstly, arrangements of administrative tasks and basic land management policies of the state should be obeyed; difficult work of land function adjustment and coordination should be avoided in planning and design; basic farmland should be protected and pollution sources should be controlled to maintain and improve river water quality; community environmental improvement is a compulsory task, which needs to be actively implemented and completed; development of tourism industry in the community should be promoted.
Based on the opinions of residents and managers in Changtian Community, consensuses on future development can be formed:
Improve the community environment and dismantle illegal buildings;
Keep the current function of landscape and avoid changes of land function;
Increase the compound function of existing land and enhance the tourism value and economic value of the community;
On the basis of farmland and ecosystem protection, adjust some of the lands, change the crop types, and develop a characteristic economy.
To compare three schemes qualitatively, ecosystem service values are calculated and compared (
Figure 17). As shown in
Figure 15, supply service, regulating service, supporting service, and cultural service of three schemes and present land use are compared. Four service values of different schemes differ from each other. Therefore, considering one service value is far from enough. All aspects should be considered, so that its comprehensive value can be maximized and the community can serve better.
Based on the comments from residents and managers of the community, an optimized scheme is proposed and the layout is shown in
Figure 15. The optimized scheme is shown in
Figure 17. The optimized scheme includes five aspects of the suggestions:
The optimized scheme takes environmental renovation and ecotourism into account to realize the balance between protection and economic development;
Delimit clear main functional areas to form functional blocks with different characteristics;
Keep the existing cultivated land area and improve the quality of cultivated land; keep the boundary and reduce the difficulty of land-use adjustment;
Utilize the land types such as garden and fish pond, increase the leisure tourism functions such as sightseeing, picking, recreation, etc., which have less impact on the environment;
Focus on the improvement of waterfront space, combine the ecological restoration with sightseeing and recreation functions, and enhance the cultural value of the waterfront space.
The optimized scheme (
Figure 18) combines the present land use and future development, which includes environmental protection, farmland protection, and ecotourism. It suits the administration policy and the anticipation of residents.