不同视角下基于InVEST模型的流域生态补偿标准核算——以渭河甘肃段为例

补偿标准是生态补偿项目研究的核心内容。为提高补偿标准的可操作性,以渭河干流甘肃段为研究区,基于流域生态补偿标准范围界定,在考虑耕地向多种林地转化情况下采用In VEST模型和加权法核算流域新增生态服务量,并以新增生态服务价值为补偿上限,农户机会成本为补偿下限,先从国家新一轮退耕还林政策导向视角,探讨15°—25°和25°以上坡耕地退耕还林的差异化补偿标准。再从利益公平分配视角,耦合机会成本投入与生态系统服务产出,探讨生态补偿净收益不同地区的差异化补偿标准。结果表明:(1)渭河干流甘肃段退耕还林,生态补偿标准范围为146.39—481.98万元km~(-2)a~(-1)。(2)重要水源地一级保护区和保留区迎水面15°—25°坡耕地全部退耕还林需补偿金额13.95—33.55亿元。25°以上坡耕地全部退耕还林需要补偿金额12.96—28.35亿元。(3)各县/区比较,退耕还林净收益麦积区最大,陇西县最小。其生态补偿范围分别为202.23—727.92、96.99—136.53万元km~(-2)a~(-1)。

Standard of payment for ecosystem services in a watershed based on InVEST model under different standpoints: a case study of the Weihe River in Gansu Province

Standard of payment is the core content of a payment for ecosystem services (PES) project. Considering the conversion of farmland to a variety of forestlands, based on the definition of the PES standard range, we calculated the increments of ecosystem services in the Weihe River Basin in Gansu Province with the InVEST model and the weighted method, using the land use, meteorological, soil, socioeconomic, and questionnaire survey data, to improve operability of the payment standard. The difference between forestland and farmland in ecosystem services was used to characterize the main increments of ecosystem services of water yield, sediment retention, and water purification. The number of ecosystem services for forestland came from the weighted sum of weights (the ratio of each kind of converted forest area accounted for the total conversion area) and the number of ecosystem services per unit area of corresponding forest. Additionally, setting the increased value of ecosystem services as the payment upper limit and taking the opportunity cost of participators as the lower limit, the differentiated PES standard of returning farmland to forest in 15°-25° and above 25° sloping farmland were studied from the standpoint of a new round of national policy oriented towards returning farmland to forest. Furthermore, from the standpoint of fair distribution of benefits, the differentiated PES standard in different net income regions, coupled with opportunity cost input and ecosystem services output, were explored. The results showed that the PES standard of returning farmland to forest was range from 146.39×10⁴ Yuan km^-2 a^-1 to 481.98×10⁴ Yuan km^-2 a^-1 in the Weihe River Basin of Gansu Province. With returning farmland to forest, the annual value of water yield would increase by 1.49×10⁴ Yuan/km²; the annual value of sediment retention would increase by 479.55×10⁴ Yuan/km²; and the annual value of water purification would increase by 0.94×10⁴ Yuan/km². Secondly, the results showed that the areas in sloping farmland (15°-25°), which were the upstream faces of important drinking water sources in first-level protected and reserved areas, accounted for approximately 10% of the sloping farmland. If all above-mentioned areas in sloping farmland (15°-25°) changed to the forestland, PES funds of 13.95×10⁸ Yuan to 33.55×10⁸ Yuan would be needed. For those above 25°, PES funds ranging 12.96×10⁸ Yuan to 28.35×10⁸ Yuan would be needed. For the areas in sloping farmland (15°-25°), the increased annual values of water yield, sediment retention, and water purification were 13.35×10⁴, 337.42×10⁴, and 0.81×10⁴ Yuan/km², respectively. Values for the areas above 25° were 15.99×10⁴, 302.90×10⁴, and 0.76×10⁴ Yuan/km², respectively. The ranges of PES for the areas in sloping farmland (15°-25° and above 25°) were 146.39×10⁴ to 351.58×10⁴ Yuan km^-2 a^-1 and 146.39×10⁴ to 319.65×10⁴ Yuan km^-2 a^-1. Finally, compared with other districts, the maximum net income of returning farmland to forest appeared in the Maiji district, and the minimum was represented in the Longxi district. Their ranges of PES were 202.23×10⁴ to 727.92×10⁴ Yuan km^-2 a^-1 and 96.99×10⁴ to 136.53×10⁴ Yuan km^-2 a^-1, respectively.