Piloting ecosystem services valuation in Uruguay

Traditional economic valuations do not explicitly consider nature’s value, making it invisible and preventing unbiased decision making. When failing to consider ecosystems in the assessment of an activity or project under evaluation, we implicitly assign them a value of zero and therefore we ignore whether and to what degree nature is affected. Negative consequences are generally seen after the fact, and the margin to prevent further deterioration or remediate the damages already caused is usually smaller than if it had been considered from the beginning. Moreover, gross domestic product (GDP), the main economic indicator to measure progress, grows when some ecosystem services (ES) are degraded and artificially replaced (WAVES, 2014). This is usually interpreted as a positive signal, even when it may be compromising future development and prosperity. Diverse methods have been developed so far in order to measure ecosystem services value (United Nations et al., 2021). Some of them involve a price that is directly observable (e.g. land rent) or it is obtained from markets for similar goods and services (e.g. if mushrooms from one forest are commercialized, but those from a similar forest are not, the prices observed in the former can be applied to the latter). In other cases, the price for the ES is embodied in a market transaction (e.g. resource rent, productivity change and hedonic pricing methods) or is based on revealed costs (e.g. averting behavior and travel cost methods) or expected costs (e.g. replacement cost or avoided damage costs methods). A summary of the most relevant literature on this topic can be found in the Ecosystem Services Valuation Database (https://www.esvd.net/). This research shows how some of those approaches can be applied in a sub basin of Santa Lucia river catchment as a case study, and provides a comparison of the results obtained through alternative valuation methodologies. This type of assessments are scarce in the Latin American context. The selected services are soybean, corn and wheat provisioning services, grazed biomass provisioning services for meat and milk production, drinking water supply and water purification (through the retention and breakdown of nutrients made by riparian forests). The methods used to estimate the value of these services are land rent, resource rent, replacement costs and avoided damage costs. The period of analysis is 2014 to 2019. The physical flows of ecosystem services, which is the base for later economic valuation, is obtained from a model developed in SWAT (Soil and Water Assessment Tool) in Borges et al. (unpublished). We focus on the Santa Lucía river basin, which provides drinking water for about 60% of Uruguay’s populations. For this analysis data is mainly obtained from the Agricultural Statistics Office of the Ministry of Livestock, Agriculture and Fisheries (DIEA - MGAP), the national accounts published by the Central Bank (BCU) and the national drinking water supply company (OSE). Estimations suggest that the value of soybean and milk provisioning services are the highest. Additionally, the highest values are obtained by applying the replacement cost method, which may indicate that the methods based on directly observed market values (land rent) and on residual values (resource rent) have a tendency to underestimate ecosystem value and that, artificially substituting the service provided by nature may be very expensive. These results can be used in different ways. On the one hand, the value of the ecosystem services that are not included in the current GDP (for instance, water purification) can be added, in order to better reflect the influence of nature on the economy. On the other hand, the contributions of ecosystems in the supply of goods and services already accounted in the value-added calculations (typically provisioning services), can be distinguished from human contributions. Additionally, ecosystem services values can be used in social cost benefit analysis of multiples measures or projects and in the valuation of environmental assets (as they reflect the value of all the services they provide), among others. References: Borges, M., Hastings, F., Hein, L. and Carriquiry, M. (unpublished) Modelling hydrological ecosystem services and externalities using SWAT and an ecosystem accounting approach. Wageningen University and Resaerch United Nations et al. (2021). System of Environmental-Economic Accounting— Ecosystem Accounting (SEEA EA). White cover publication, pre-edited text subject to official editing. Available at: https://seea.un.org/ecosystem-accounting WAVES (2014) Natural capital accounting (NCA) and payments for ecosystem services - frequently asked questions. World Bank Group.

传统经济估值并未明确考量自然的价值，这使得自然价值被遮蔽，也阻碍了决策的公正性。当我们在评估某项活动或项目时未纳入生态系统考量，实则默认其价值为零，进而忽略了自然是否以及在何种程度上受到影响。负面影响往往在事后才显现，此时防止进一步恶化或修复已造成损害的空间，通常远小于从一开始就将自然纳入考量的情况。
此外，作为衡量经济发展的核心经济指标，国内生产总值（gross domestic product, GDP）在部分生态系统服务（ecosystem services, ES）遭到退化并被人工替代时反而会增长（WAVES, 2014）。即便这可能损害未来发展与繁荣，这类增长通常仍被视为积极信号。
迄今为止，学界已开发出多种生态系统服务价值测算方法（United Nations et al., 2021）。部分方法依托可直接观测的价格（如土地租金），或从同类商品与服务的市场中获取价格（例如，若某森林产出的蘑菇实现商业化，而另一类似森林未实现，则可将前者的观测价格应用于后者）。另有一类方法的生态系统服务价格蕴含于市场交易之中（如资源租金、生产率变化与特征价格法），或基于揭示性成本（如防护行为法与旅行成本法），抑或预期成本（如重置成本法与避免损害成本法）。关于该主题的核心文献综述可参见《生态系统服务估值数据库》（Ecosystem Services Valuation Database, https://www.esvd.net/）。
本研究以圣卢西亚河流域的一个子流域为案例，演示了部分上述方法的应用，并对比了不同估值方法得到的结果。这类评估在拉丁美洲地区较为匮乏。
本次研究选定的生态系统服务包括：大豆、玉米与小麦供给服务，用于肉奶生产的放牧生物质供给服务，饮用水供给服务，以及通过河岸森林留存与分解养分实现的水质净化服务。本研究采用的估值方法包括土地租金法、资源租金法、重置成本法与避免损害成本法，分析时段为2014年至2019年。生态系统服务的实物流量是后续经济估值的基础，其数据源自Borges等人（未发表）基于SWAT（Soil and Water Assessment Tool）开发的模型。
本研究聚焦圣卢西亚河流域——该流域为乌拉圭约60%的人口提供饮用水。本次分析的数据主要来自乌拉圭畜牧、农业与渔业部农业统计办公室（DIEA - MGAP）、乌拉圭中央银行（BCU）发布的国民经济核算数据，以及全国饮用水供应公司（OSE）。
估算结果显示，大豆与奶业的供给服务价值最高。此外，采用重置成本法得到的价值最高，这表明依托直接观测市场价值的方法（土地租金法）与基于剩余价值的方法（资源租金法）往往会低估生态系统价值，而人工替代自然提供的服务往往成本高昂。
这些结果可应用于多个场景：其一，可将当前国内生产总值未纳入的生态系统服务价值（如水质净化服务）纳入核算，以更准确地反映自然对经济的影响；其二，可区分出生态系统在已纳入增加值核算的商品与服务供给（通常为供给服务）中所做的贡献，与人类活动的贡献；此外，生态系统服务价值还可用于多项举措或项目的社会成本收益分析，以及环境资产估值（因其反映了环境资产提供的全部服务价值）等诸多场景。
参考文献：
Borges, M., Hastings, F., Hein, L. and Carriquiry, M. (未发表) 基于SWAT与生态系统核算方法的水文生态系统服务与外部性建模. 瓦赫宁根大学与研究中心
United Nations et al. (2021). 环境-经济核算体系——生态系统核算（System of Environmental-Economic Accounting— Ecosystem Accounting, SEEA EA）. 预编辑文稿，待正式编辑后出版，可于https://seea.un.org/ecosystem-accounting获取
WAVES (2014) 自然资本核算（Natural capital accounting, NCA）与生态系统服务付费——常见问题解答. 世界银行集团