3. Results
In 2020, the potential GEP for Miyun County was 254.32 billion yuan. Among all kinds of ecosystem products, the water retention service contributed the highest (119.5 billion yuan), accounting for 47% of the potential GEP in Miyun County, followed by natural landscape (52.16 billion yuan). Wetland ecosystems were the main contributors to water retention services. The value of ecosystem products provided by wetlands was almost 4.5 times that provided by the other areas (per unit area) combined.
In 2020, the actual GEP in Miyun County was 53.28 billion yuan. Among all kinds of ecosystem products, the contribution of climate regulation service was the highest (17.46 billion yuan), accounting for 32.8% of the actual GEP in Miyun County, followed by water retention service (11.86 billion yuan). Forest ecosystems contributed the most to climate regulation. The value of ecosystem products contributed by wetlands per unit area was the highest at 96 yuan/m2.
In 2020, among all types of ecosystems in Miyun County, wetlands contributed the highest potential GEP (141.92 billion yuan), followed by forests (61.19 billion yuan) and urban ecosystems (0.4 million yuan). Forests contributed the highest actual GEP (20.49 billion yuan), followed by wetlands (14.47 billion yuan). The contribution of the urban ecosystem was the same as its contribution to potential GEP (0.4 billion yuan). Although the demand in urban ecosystems was theoretically high, owing to its low supply capacity, the ecosystem products provided by the urban ecosystem were utilised by residents and contributed to the actual GEP. The actual GEP accounted for approximately 21% of the potential GEP, indicating that the overall use intensity of ecosystem products in Miyun County remained low relative to the service supply capacity. The difference between the potential and actual GEPs shows the scope for vast exploitable space for water retention and natural landscape services in Miyun County and that the local government can further rationally promote local water resource utilisation and tourism development.
The spatial distribution patterns of potential GEP in Miyun exhibited apparent spatial heterogeneity. The potential GEP was high in the Northwestern region and the surrounding areas of the Miyun Reservoir, mainly distributed in PLT, SC, HWC, and MCY town. Areas with high values of ecosystem products were affected mainly by the Miyun Reservoir and Chaobai River systems, with rich vegetation, high water retention and climate regulation service values, and relatively complete ecological functions. Therefore, the supply potential was high. The potential GEP was low in the Southwest region, mainly distributed in KLC, KYC, and MYT town, and the low-value area is mainly distributed around the economic centre of Miyun County. Water and vegetation areas were small because of the extensive distribution of construction land. Therefore, the supply potential of ecosystem products was low.
The distribution pattern of the actual GEP in the Miyun area also exhibited obvious spatial heterogeneity. High actual GEP was primarily associated with the southwest region, such as KLC, KYC, and MYT town, with rapid economic and social development, high levels of regional economic development, dense populations, and high intensities of ecosystem product use. Areas with low actual GEP, such as HCT and PC towns, were mainly distributed in the Northeast. Owing to their low degree of development and utilisation, poor regional accessibility, and low population, the intensity of the use of ecosystem products was low.
The difference between the potential and actual GEPs in Miyun tended to be lower in the Southern region and higher in the Central and Northern regions, indicating some imbalance. From the perspective of spatial distribution, GEP surplus areas were mainly distributed in PLT and SC towns and other Northwestern regions. In the Southwest regions, including KLC, KYC, TY, and MYT towns, the regional economic development speed is fast, the construction land area is large, and the ecological resource utilisation intensity is high. Consequently, the potential supply of ecosystem products could not meet the needs of residents, as reflected in the GEP deficit. In addition, there is a trend of spatial expansion from the economic centre in the Southwest to the surrounding SLP, HNC, HTK towns, and other regions. The GEP surplus was high in the Northwestern region, with an excellent ecological environment and relatively low population density. The areas centred around the Miyun Reservoir, such as HWC, MCY, and TCT town, are close to the reservoir, rich in water resources and fishery products, and have strong climate regulation ability, which brings high tourism and cultural value. As a result, the potential GEP of the reservoir around the bank and the supply potential were high, differing substantially from the high-deficit areas outside the bank.
For natural ecosystems (forests, shrubs, grasslands, and wetlands), the potential GEP was positively correlated with the actual GEP (R2 = 0.61). It follows that, within the scope of natural ecosystems in a region, the greater the supply intensity of ecosystem products, the higher the use intensity. However, due to human interference’s intensity, farmlands, towns, and bare lands did not show apparent correlations. Correlation analysis of the driving factors with potential and actual GEP showed that the natural ecosystem area (R2 = 0.88) and vegetation coverage (R2 = 0.73) were the main driving factors affecting potential GEP in Miyun County. The GDP (R2 = 0.84) and population (R2 = 0.82) were the main driving factors affecting GEP in Miyun County.