*2.3. Method*

The general goal of sustainable development in an existing industrial zone is realized through the synergy of the environmental, economic, and social subsystems that constitute the system, so as to eliminate the system's current degradation and stagnation and improve it considering the renewal and utilization of land resources as the goal [50–52]. This study emphasizes that, under the premise of a clear overall goal and vision, the favorable factors of social and economic subsystems can be used to create landscape on the material elements of the environmental subsystems (Figure 3) to achieve social, economic, and environmental improvements, and sustainable development [53–55].

**Figure 3.** Relationship between subsystems in existing industrial zones.

An existing industrial zone is a composite ecosystem with economic development as its main body. The transformation and upgrading of existing industrial zones cover the most complex elements and combinations. In the meantime, the transformation and upgrading of existing industrial zones is a spiraling dynamic and sustainable development process, in which the industrial zone must be altered from its past state; this is the top priority in solving sustainable development issues in the human society. The main feature of the sustainable development evaluation model is to highlight the baseline status of ecosystem services, while considering how to improve the people's overall satisfaction as much as possible [36,56,57].

Existing industrial zones can be regarded as complete composite ecosystems [58,59]. On this basis, we constructed a green transformation and sustainable development evaluation model. Each subsystem was composed of the social, economic, and environmental elements of the existing industrial zones. We found that through the optimization of each element index, ecosystem services can be maintained and improved, with sustainable benefits provided to existing industrial zones. This model of a continuous optimization of the elements of existing industrial zones is called the sustainable development evaluation model of the green transformation of existing industrial zones.

The sustainable development evaluation model of existing industrial zones requires a complete data system embracing data on land, industry, ecology, architecture, culture, and landscape in the respective industrial zones [60–62]. In this process, the sustainable development of the existing industrial zone will be realized by means of industrial transformation and upgrading, compound land use, ground buildings, the green transformation of structures, ecological environment restoration, the construction of characteristic landscape, the continuation of culture, and so on (Figure 4).

The transformation of existing industrial zones is an evolving process (from unsustainable to sustainable). During the process of construction, dynamic monitoring and real-time data feedback can be implemented, while adjustments, improvements, and renovation can be made according to changes in the situation during the implementation process (Figure 5).

In the sustainable development evaluation model, an index system of six dimensions (land, building, industry, ecology, landscape, and culture) is constructed. Each dimension has its sustainability score and can be optimized in different dimensions under the premise of ensuring ecological constraints. In the process of green transformation, the data for each dimension are reflected in the indicators (Figure 6). Before and after the transformation, there will be changes in the indicator data. The comparison of sustainable development

evaluation reflects the green and ecological effects of the transformation means. According to the scoring results of each indicator, the improvement in each direction can be reflected.

**Figure 5.** Data model of sustainable development in existing industrial zones.

**Figure 6.** Comparison before and after transformation.
