Synergies evaluation and influencing factors analysis of the water–energy–food nexus from symbiosis perspective: A case study in the Beijing–Tianjin–Hebei region

In the context of global population growth and environmental degradation, research on the synergies of the water–energy–food (WEF) nexus is important for sustainable regional development. Using symbiosis and synergy theories, the authors constructed a synergy evaluation index for the WEF nexus and used the set pair analysis-variable fuzzy sets model to analyze the WEF nexus synergies in the Beijing–Tianjin–Hebei region (BTH) of China, from 2005 to 2017. The main factors affecting WEF nexus synergies were also analyzed, with results indicating that: 1) the WEF nexus synergies were the best in Beijing, followed by the BTH as a whole, Tianjin, and then Hebei. We also found that WEF nexus synergy grades have been gradually improving over time, with Beijing improving the most, and Tianjin the least. 2) The WEF nexus synergy grades in each region, for symbiotic units, symbiotic relationships, and symbiotic environments, have also gradually improved. And symbiotic relationship synergies were better than symbiotic environment synergies than symbiotic unit synergies. 3) The WEF nexus symbiotic unit synergies were strongest in Tianjin, followed by Beijing, the BTH as a whole, and then Hebei. The symbiotic relationship synergies were strongest in Beijing, followed by Hebei, the BTH as a whole, and then Tianjin. The symbiotic environment synergies were also strongest in Beijing, followed this time by the BTH as a whole, Tianjin, and then Hebei. 4) Economic factors and symbiotic unit synergies were found to be the aspects most influential on WEF nexus synergies in each region. In addition, symbiotic relationship synergies were found to have important impacts on the WEF nexus synergies in Hebei and the BTH as a whole. Overall, we were able to conclude that the methodology developed in this study provided a scientific basis for synergy optimization in the context of a regional WEF nexus.