## 4 Discussion  
Within the EFM system, there are considerable controversies and uncertainties about the ESV evaluation of water ecosystems (rivers, wetlands and lakes) and built-up land. Compared with land ecosystems such as cropland and forest, which are relatively \"stable\", the water ecosystem uses liquid water with fluidity as the carrier and carries out complex material and energy interactions with other ecosystems and ecological environments. The spatial differences in water ecosystems are far from those in land ecosystems. The benefits and values of water ecosystem services are closely related to watershed runoff, water environment quality, aquatic biological diversity and aquatic biomass, but it is very difficult to obtain these data and conduct quantitative evaluations. Therefore, in the next stage of the study, we can consider introducing a series of water ecosystem indicators and develop an NPP-like indicator to evaluate the service capacity of water ecosystems, which can be used to modify the regional and interannual service functions and their value in the EFM. In most studies of ESV, built-up land is generally considered a \"consumer\" of ecosystem services, and its ecosystem service function and the value provided by it are set to 0. In fact, as an important part of the urban compound ecosystem, urban ecological land is composed of small green spaces and waters in the city and plays an important role in protecting the urban ecosystem and improving the urban living environment and the living quality of residents. Changes in the area and spatial distribution of urban ecological land have an important impact on urban ecological security [49; 50]. Therefore, the planning and construction of urban ecological land is an important comprehensive approach to solving the contradiction between the urbanization process and natural ecological protection. The various ecological services provided by urban ecological land have both natural and social attributes [10; 27]. Urban ecological land not only maintains the stability of the energy flow, material flow and information flow of the ecosystem itself and guarantees the security of the ecological base of urban development but also provides multiple ecosystem services,  
Figure 12: ESV coefficient application in GHM IDMP for evaluating ESV lost in land resource collaborative allocation: an example area in Nansha District (the specified project name is covered). such as supply, regulation, support and culture for human beings. These are the most direct benefits of ecosystem services enjoyed by urban residents in their daily lives. Therefore, the ecosystem service of ecological land in urbanization areas should not be ignored. For the evaluation of ecosystem service functions of small-scale ecological land in urban areas, it is necessary to introduce comparable quantitative ecological indicators (such as the green index or enhanced vegetation index), combined with more detailed land use data for comparing the difference in ecosystem service capacity between urban green space and land ecosystems, and the quantitative ecological indicators can be used as modification coefficients to evaluate the ecosystem service function and its value provided by urban ecological land in the EFM. The ESEV is a quantitative indicator representing ecosystem functions and capabilities. To convert ecosystem functions into an ESV of economic value, a monetization unit is needed as a proxy. In [PERSON]'s et al. [24] EFM, this proxy was the standard value volume called the \"\(D\) value\", which represents the annual economic benefit of a unit area of cropland. However, due to various reasons, such as the lack of modification methods and ecological and social statistics, many researchers directly used the \(D\) value of 2010 in China calculated by [PERSON] et al. in the study of different regions and years [25]. This approach ignores the ecosystem service capabilities and socioeconomic regional and interannual differences and variations.