3. Methods3.1. Assessing urban environmental resourcesWe developed a framework for valuating environmentalresources in the city of Shenzhen (Fig. 2). Based on this framework,we also developed a series of formulas to compute the values ofdifferent resources and services in this urban environment.The generalized environmental resource value (GERV) isdefined as the total sum of ecosystem service value (ESV),atmospheric environment capacity value (AECV), water envi-ronment resource value (WERV), and land value (LV), i.e.,GERV = ESV + AECV + WERV + WERV, in which the water envi-ronment resource value is the sum of water environment capacityvalue (WECV) and water resource value (WRV) (Fig. 2). To facilitatecomputation and comparison, we also defined Environmentalresource value in a narrow sense (ERVNS) as the summation ofecosystem service value, atmospheric environmental capacityvalue, and water environmental capacity value.To compute ESV, we considered six different ecosystem ser-vices: organic matter production, CO2absorption, O2release,nutrient cycling, water conservation, and soil conservation (Yu,Jiang, Kang, Tian, & Duan, 2011). AECV included four items: SO2(kg/year, sulfur dioxide), NO2(kg/year, nitrogen dioxide), TSP(kg/year, total suspended particles), and PM10(kg/year, particleswith aerodynamic equivalent diameter of less than 10 m).The loss of atmospheric environmental capacity in value wascalculated with the “shadow price method”. The environmentalcapacity loss was estimated as all the costs for the governanceof urban air pollution. Based on the actual air quality situationin Shenzhen, we focused on the loss caused by SO2and PM10.The full recovery cost of SO2was calculated as: SO2recoverycost = transaction price (P) × emission (Q), where P (RMB/t) is theaverage treatment cost of atmospheric pollutants (SO2or PM10)and Q(t) is the emission quantity. According to the pollutant charg-ing standards, the pollution equivalent of atmospheric pollutantsother than SO2is calculated as: pollutant equivalent = emission(kg)/equivalent value (kg). The emission trading price was set to6 RMB/kg in this study. The treatment costs for PM10and fumewere estimated as per Ordinance on Levy, Usage and Manage-ment of Pollutant Charges (State Council Order No. 369) and LevyFigStandards and Calculation Methods of Pollutant Charge. The atmo-spheric environmental capacity for Shenzhen in 2005 was obtainedfrom Li, Huang, Zhang, and Pan (2010).Water environmental capacity value (WEC) as computed as:WEC = [(CODground+ CODoffshore) + (NH3-Nground+ NH3-Noffshore)].The capacity values of COD and NH3-N were calculated in accor-dance with the pollutant emission charging standards in Ordinanceon Levy, Usage and Management of Pollutant Charges (State Coun-cil Order No. 369). Pollutant charge was estimated as the pollutionequivalent of pollutants multiplied by 0.7 RMB (COD equivalent is1 kg, the ammonia equivalent is 0.8 kg). The water environmentalcapacity for Shenzhen in 2005 was obtained from Li et al. (2010).Water resources value was calculated as: WRV = unit price of waterresources × quantity/area of water. Unit price of water resources inShenzhen in 2005 was calculated according to the average waterprice of various industries in Shenzhen which was derived fromthe Shenzhen Water Resource Bureau (SWRB, 2012).Land value includes four items: official land value, commercialland value, industrial land value, and residential land value. Dataof land value accounting and mapping in Shenzhen were based onthe benchmark land prices in Shenzhen (in May 2006), namely thebasic land prices of four categories of official land, commercial land,industrial land, and residential land. The data were acquired fromShenzhen Land Resource Bureau. The basic data included electronicbase maps of 92 benchmark land prices, and one electronic basemap of administrative divisions of Shenzhen.According to the Land Use Rights Grant Regulations of SSEZ (Sec-ond Amendment, 1998), the maximum number of years of landuse right granting is determined in accordance with the land usetype: residential land value = the benchmark price of residentialland/70; industrial land value = the benchmark price of industrialland/50; commercial land value = the benchmark price of com-mercial land/40; official land value = the benchmark price of officeland/50. Denominators in the above formulas are the grantingperiod (in years). On the basis of the above four types of land valueestimation, and taking into account the equal probability for theabove land uses, we adopted the average value of the above fourtypes as the average land value.3.2. Planning of urban ecological networkAll remote sensing data used in this study were derived from2005 Landsat TM imagery delineated for Shenzhen, in which theland-use classification system was divided into farmland, built-up, forest, orchard, and water (Shi, Yu, Jiang, Wang, & Xu, 2012).We defined ecological core areas (ECAs) as the areas of natural,semi-natural ecological patches with strategic significance for theprotection of regional ecological diversity and the improvement ofenvironment quality. The standards for qualifying ECAs in Shen-zhen were: (1) water source protection areas, scenic spots, naturereserves, stretches of primary farmland protection areas, forests,and country parks; (2) soil and water conservation, mountains andwoodlands with slope over 25◦and uplands with elevation over50 m are included; (3) main trunk rivers, reservoirs and wetlands;(4) green space for the maintenance of ecosystem integrity; and(5) peninsulas and other ecologically important coastal areas. ECAswere spatially delineated by the support of digital elevation model(DEM), land use/cover map (2005), and the Shenzhen governmentalMaster Plan for land use.The functions of ecological corridors in Shenzhen include nat-ural ecological functions and provision of a variety of ecosystemservices for the urban population. Due to the rapid economicgrowth, urban expansion, and disorderly changes in landscape pat-tern, urban green space in Shenzhen has drastically reduced insize and connectivity, now mostly existing as islands in the moun-tainous areas. To improve the ecological integrity of the urbanlandscape, this study considered different scenarios for design-ing urban ecological corridors. Specifically, these scenarios weredesigned from the perspectives of enhancing species migration andbiodiversity conservation, sewage purification, noise reduction,dust and air purification, water conservation, and flood regulation.