Spatially-explicit quantitative relationship for a potential PES mechanism:Cascade hydropower development in Yarlung Zangbo River Basin, China

Payment for ecosystem services(PES) is of great importance for the sustainable development of mountain areas, key hotspot regions for the provisioning of ecosystem services. At present, PES researches mainly focus on forest protection, carbon sink trading, and water protection. As an important industry in mountainous areas, cascade hydropower development has generated substantial economic benefits accompanied by social and ecological impacts. However, efficient PES mechanisms to deal with hydropower generation in mountain areas are still unavailable. Therefore, the lacking of PES in mountain systems limits the development of those areas, and compromise the sustainability of hydropower development. The critical reason lies in the lack of a scientific method that can quantitatively analyze the relationship of hydropower stations with a geographical scope at county level(i.e., quantifying the water yield service provided by each county within the cascade hydropower development basin), and with different hydropower enterprises. We use the Yarlung Zangbo River Basin of China as case study area, one of the major hydropower development basins in China. First, we used Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST) model to map water yield service. Then, we calculated the value of water yield service by relating the water yield to the gross output value of hydropower stations. We revealed the relationship(e.g., hydropower stations and identified counties) between the payers and the payees of ecosystem services through mapping and quantifying the provisioning regions in the supply of water yield service and the users(hydropower enterprises). Finally, we discussed the current situation of benefit distribution in cascade hydropower development basin based on the supply and use of the water yield service. The results showed that 1) the spatial distribution of the value of water yield service is uneven: the upper reaches are highvalue areas;the eastern region is higher than the western region;and the maximum value(USD 119.2$/km2) is 34 times higher than the minimum value(USD 3.5 $/km2). 2) We found that four state-owned enterprises are the direct beneficiaries of water yield service, and 37 counties are suppliers, among which Gongbogyamda, Lhari and Damxung are the first level of supply. 3) Each hydropower station is provided with water yield service by several counties, and the value of water yield service varies greatly in each county, showing spatial differences. 4) Most counties are only partially involved in the process of water yield service being used by hydropower stations(i.e.,the boundary of water yield service is inconsistent with the administrative boundary). 5) Huaneng Tibet Yarlung Zangbo River Hydropower Development and Investment Co., Ltd. gets the greatest value(USD 1.8million $) from the use of water yield service, while China Energy Tibet Electric Power Co., Ltd. gets the smallest(USD 389.1 thousand $). 6) Counties near the lower reaches have gained more economic benefits, while the water yield service they provide have the lowest contribution to hydropower production. Our approach linked water yield ecosystem service and hydropower development effectively, and revealed their complex eco-economic relationship between producers and beneficiaries of ecosystem services, which provides key insights for the designing of a potential PES mechanism.

Spillover effect offsets the conservation effort in the Amazon

Diverse conservation efforts have been expanding around the globe, even under the stress of increasing agricultural production. A striking example is the supply-chain agreements put upon the Amazon forest which had reduced deforestation by 80% from the early 2000s （27,772 km2） to 2015 （6207 km2）. However, evaluation of these conservation efforts usually focused on the impacts within the Amazon biome only, while the effects that spill over to other areas （e.g., displacement of environmental pressure from one area to another） were rarely considered. Ignoring spillover effects may lead to biased or even wrong conclusions about the effectiveness of these conservation efforts because the hidden cost outside the target area of conservation may offset the achievement within it. It is thus impor- tant to assess the spillover effects of these supply-chain agreements. In this study, we used the two supply-chain agreements （i.e., Soy Moratorium and zero-deforestation beef agree- ment） implemented in the Amazon biome as examples and evaluated their spillover effects to the Cerrado. To achieve a holistic evaluation of the spillover effects, we adopted the telecou- piing framework in our analysis. The application of the telecoupling framework includes the interactions between distant systems and extends the analytical boundaries beyond the sig- natory areas, which fill the gap of previous studies. Our results indicate that the supply-chain agreements have significantly reduced deforestation by half compared to projections within the sending system （i.e., Para State in the Amazon, which exports soybeans and other agricultural products）, but at the cost of increasing deforestation in the spillover system （i.e., a 6.6 time increase in Tocantins State of the Cerrado, where deforestation was affected by interactions between the Amazon and other places）. Our study emphasizes that spillover effects should be considered in the evaluation and planning of conservation efforts, for which the telecoupling framework works as a useful tool to do that systematically.