Optimizing safe and just operating spaces at sub-watershed scales to guide local environmental management

The safe and just operating space (SJOS) concept provides a promising framework tool to help guide social-ecosystem management and sustainable global development goals (SDGs). Due to spatial differences in geographic background and economic development, proportioning these elements according to global, regional and local scales is a necessity for sustainability governance. Achieving SDG targets requires guidance according to SJOS environmental and social boundaries. Here, integrating planetary boundaries (PBs) with the SJOS framework is explored and focused towards the sub-watershed scale in the Chaohu watershed, China. Assessment of environmental and socio-economic dimension changes in this watershed incorporates data taken from long-term monitoring, surveys and anthropogenic impact records in lake sediment sequences. These are used to explore spatial and temporal differences in key environmental change processes and social well-being measures in the watershed. The interrelationships with identified prioritized PB limitation indicators within the sub-watersheds were evaluated numerically. Results indicate four PB biogeophysical dimensions, water quality, chemical pollution, air pollution and ozone depletion all operate in the Chaohu watershed and exceed safe boundary limits. However, large differences exist between the four main sub-watersheds. Environmental pressures in the two western sub-watersheds are considerably greater than those in eastern regions. Most social indicators selected for the whole watershed conform well to PB limits considered necessary for achieving sustainable development goals (SDGs), especially food (SDG 2), health (SDG 3), sanitation services (SDG 6c) and consumption (SDG 12). Based on quantifiable environmental change trends in each sub-watershed and social development in the last decades, we identify, water quality, chemical pollution, and soil stability PB dimensions as exceeding safe operation limits. These dimensions are prioritized for environmental management and harmonization with SDG targets. Water utilization intensity (SDG 6a) and forest cover (SDG 15) are social development priorities across the whole Chaohu watershed. Redundancy analysis identified GDP per capita as well as changes in forest and vegetation cover as key drivers of environmental degradation throughout the watershed. While not all 17 SDGs are considered, initial results of this study provide a rational base for informing systems management and policy, guiding the attainment of SDG targets, and communicating the importance of revealing environmental change trends. Requirements for sustainable development of human society locally and regionally are, within limits of the data available, identified by matching SJOS boundaries with SDG targets. Strengthening time-track data for the key drivers of change and combining with emerging socio-economic factors is needed to better define specific SDG progress in terms of achieving calibrated environmental boundaries.