Integrated land restoration impact assessment in the Chinese Loess Plateau

Samenvatting

Land restoration has been implemented worldwide as an effective way to combat land degradation and improve biodiversity. As one of the most severely eroded regions in the world, the Chinese Loess Plateau has been given a lot of attention by the national government since the 1970s in terms of land restoration policies, most recently and most comprehensively by the Grain for Green Project (GGP) (1999-2021). The main goal of the GGP was to restore the ecosystem through afforestation and soil and water conservation. Over the past few decades, land restoration actions have not only altered land use and delivery of ecosystem services in the Loess Plateau, but also changed the living conditions of many of the stakeholders. The main objectives of this thesis are to comprehensively understand the hydrological, bio-physical, economic and societal impacts of land restoration in the Chinese Loess Plateau.

Using 52 published watershed case studies, a meta-analysis was conducted to describe the impacts of changes in land use and climate on streamflow in the Chinese Loess Plateau. The majority of the studied watersheds showed that the streamflow decreased significantly (-0.46mm/year over the period 1959-2015). 64% of this decrease in streamflow can be attributed to land use changes and 36% to climate change. 

Subsequently, based on ecological models and statistical data, the temporal and spatial dynamics of ecosystem services over the course of the GGP was studied. Building land use scenarios, we were able to conduct a cost-benefit analysis to estimate the monetary benefit from this land restoration project. We found significant increases in fruit production, sediment retention, habitat quality, and aesthetic landscape value, as well as learning and inspiration value over time (from 2000 to 2018). We also found decreases in timber production and water yield. The majority of county-level ecosystem service bundles have transitioned from focusing on timber production to focusing on aesthetic landscape value. Meanwhile, the total monetary value of the ecosystem services minus restoration costs reached a net present value of 19.41 billion RMB over the period 2000-2020 as compared to the scenario without land restoration.

We also surveyed 150 stakeholders to understand their perceptions on current and future land restoration policy and its impacts on ecosystem services. The survey results indicated that 72% of stakeholders supported current land restoration, with government officers reporting the highest values and tourism operators the lowest. Only 51% of stakeholders supported future land restoration. Some farmers could eventually decide to recultivate restored forest, mainly for economic reasons.

Overall, this thesis compiles a comprehensive study of the impacts of previous land restoration in the Loess Plateau, providing a framework for land restoration appraisal from ecological, economic and societal perspectives.  The introduction of land restoration bolsters local regulating and cultural services, and is also monetarily beneficial. Land restoration was found to induce streamflow reduction. To avoid potential conflicts, any future land restoration policy should attempt to reduce negative economic impacts for farmers. By conducting ex ante assessments of restoration alternatives and involving stakeholders in potential designs, such trade-offs can be anticipated and addressed, e.g., by diversifying tree species to be planted.