Ecological Network Analysis of a Virtual Water System in Tibet, China

With the development of the economy and urbanization, the contradiction between water use and supply is growing, and it is necessary to explore the relationship and evolutionary process of water flow in the water system from a systematic perspective. Although previous studies have analyzed the water system from a holistic point of view, a comprehensive system that considers virtual water flows is currently lacking. The present study establishes a seven-compartment virtual water system in Tibet in 2012 by combining ecological network analysis (ENA) with the input–output model. Socio-economic sectors and virtual water flows are expressed as network compartments and pathways. The information-based ENA is used to evaluate the characteristics of the virtual water system in Tibet, including its robustness and trade-offs between network efficiency and redundancy. Network control analysis is introduced to characterize the control and dependence intensities over the system, while ecological relationships between pairwise compartments are calculated using network utility analysis. The results indicate that Tibet’s virtual water system has close to optimal robustness, with higher redundancy and limited efficiency. The agriculture compartment is the main controller, while the energy supply compartment is the most dependent on the virtual water system. The overall systematic relationship that the system has is generally mutualistic and synergistic, the majority of which have a positive relationship, although the control and exploitation relationships are dominant. These results can be used to improve network robustness and are of great significance to the sustainable development of the virtual water system in Tibet.

Maintaining the Resilience and Productivity of Co-culture Systems in the Face of Environmental Change

Co-culture systems can address food security issues by intensifying production of crops and animal protein without requiring additional land area. We show how a graph-theoretic optimization model based on ecological network analysis can determine resilient co-culture strategies by controlling the presence of key species. Results of simulations on a hybrid rice and crayfish production system indicate that comparable levels of productivity can be achieved with different ecological system structures.