Abstract: Background, aim, and scope The recently emerging "Safe and Just Operating Space" (SJOS) framework highlighted the global ecological security boundaries and taken into account the achievement of key social development goals (SDGs). This framework is also important for environmental and ecological security at the regional scale and for sustainable social development. How to define the “threshold” of key environmental elements in the ecosystem is an important prerequisite for avoiding ecological degradation and maintaining important human well-being. This paper chose the typical Taibai Lake catchment in the middle and lower reaches of the Yangtze River, aiming to identify the regional boundaries in the process of monitoring ecosystem dynamics from monitoring and surveying real-world time series, thus developing a practical socio-ecological safety guidelines framework of the Taibai Lake Basin from the aspects of ecological security and social foundation. Materials and methods This paper collected the social survey data of the counties and cities around Taibai Lake and the monitoring and the sediment records (including sedimentation rate, geochemical elements, pollen, diatoms, etc.) in the past 150 years. From the two aspects of ecological security and social foundation, we built a safe and just operating space. Results The water quality, air quality, cultivated area and sediment regulation of the eight main ecosystem process in the basin exceed the environmental ceiling and are in dangerous states; sediment quality and soil stability are in cautious states; the biodiversity and flood level remained in safety. In terms of social foundation, the four social foundations of education, employment, income and clean water and sanitation have almost entered a safe and just operating space, but the social basis for clean energy and industrial innovation is relatively low. Discussion At present, especially in developing countries, the increasing social welfare and the basic needs of people face greater conflicts with environmental sustainability. The above results reflect the development characteristics of the Taibai Lake catchment in recent years that economic development and ecological environment development are not synchronized. Since the current academic community still lacks sufficient understanding of the state transition process of complex systems, there are still some pitfalls in the determination of the environmental ceiling in this study. The SJOS framework directly reflects the social development status and ecological environment status of each region through the quantitative system of environmental ceiling and social foundation, which provides a clear direction for decision makers in the management process. Conclusions In the process of development of the Taibai Lake Catchment, in addition to improving the social foundation, it is also necessary to pay special attention to the ecological pressure brought by economic development. The framework embraces both key elements of the ecological environment and socio-economic elements that are closely related to human well-being. In summary, the proposed framework helps to avoid problems that focus only on ecological security or social development in management and decision-making, and also helps the public understand the complex interaction between environmental caps and social foundations. Recommendations and perspectives This study also demonstrates multi-source environmental data, particularly paleolimnological records based on lake sediments, which can provide important long-term records for the development of regional eco-environmental safety frameworks. In addition, since the academic community still lacks sufficient understanding of the state transition process and the interactions among the social-ecological-environmental nexus, the selection of boundary indicators and the determination of ecological process thresholds can be further improved.
Keywords: Safe and Just Operating Space；environmental ceiling；social foundation；Taibai Lake catchment；paleolimnology