Climate-Land-Energy-Water Nexus Models Across Scales: Progress, Gaps and Best Accessibility Practices

Abstract

Approaches that integrate feedback between climate, land, energy and water (CLEW) have progressed significantly in scope and complexity. The so-called nexus approaches have shown their usefulness in assessing strategies to achieve the Sustainable Development Goals in the contexts of increasing demands, resource scarcity, and climate change. However, most nexus analyses omit some important inter-linkages that could actually be addressed. The omissions often stem from technical and practical considerations, but also from limited dissemination of new open-source frameworks incorporating recent advances. We review and present a set of models that can meet the needs of decision makers for analysis tools capable of addressing a broad range of nexus questions. Particular attention is given to model accessibility, usability and community support. The other objective of this review is to discuss research gaps, and critical needs and opportunities for further model development from a scientific viewpoint. We explore at different scales where and why some nexus interactions are most relevant. We find that both very small scale and global models tend to neglect some CLEW interactions, but for different reasons. The former rarely include climate impacts, which are often marginal at the local level, while the latter mostly lack some aspects because of the complexity of large full CLEW systems at the global level.

Emerging Themes and Future Directions of Multi-Sector Nexus Research and Implementation

“…While several literature reviews compare nexus models and methods (Endo et al, 2017;Kaddoura and El Khatib, 2017;Albrecht et al, 2018;Dai et al, 2018;Liu et al, 2018;Zhang et al, 2018;Abdi et al, 2020;Endo et al, 2020;Stylianopoulou et al, 2020;Purwanto et al, 2021;Vinca et al, 2021) and while new models and methodologies are necessary to advance any discipline, we found that there is a lack of and a strong need for quantitative comparison, validation, and assessment of the suitability of the large number of existing and upcoming nexus models. A good summary from Vinca et al (2021) shows the range of methodologies across several nexus models. The methodological approaches differ in a range of ways, including types of linkages between sectors (hard linked vs. soft linked), optimization vs. simulations, number of sectors included, as well as both temporal and spatial scales (local, state/province, river basin, national, continental to global).…”

“…The large and growing body of nexus literature shows that integrated and holistic management of interconnected global systems is becoming critical as the pressures on our limited and shared resources increase (Canyon et al, 2015;Siri et al, 2016;Allen et al, 2019;Hameed et al, 2019;Mabhaudhi et al, 2019;Olawuyi, 2020;Zarei, 2020). Past reviews of nexus literature (Cremades et al, 2019;Johnson et al, 2019;Simpson and Jewitt, 2019;Opejin et al, 2020;van Gevelt, 2020;Vinca et al, 2021) raised some of the same points highlighted in this study, such as the need for applied case studies, the curation of standardized data, the categorization of appropriate models for different use-cases, a shift from analysis to implementation through policy and governance mechanisms, and integration with existing multi-sector frameworks such as the SDGs. The conclusions from this paper reiterate several of these past recommendations but, in addition, highlight a concern that the scope of the nexus discipline is increasing in complexity and ambiguity as the number of new methodologies and studies grows.…”

“…Several other past studies have compared nexus methodologies (Endo et al, 2017;Kaddoura and El Khatib, 2017;Albrecht et al, 2018;Dai et al, 2018;Liu et al, 2018;Zhang et al, 2018;Johnson et al, 2019;Endo et al, 2020;Stylianopoulou et al, 2020;Purwanto et al, 2021;Vinca et al, 2021), but to date these have been qualitative due to the lack of any organized mechanism for quantitative comparisons. This perspective article highlights the need for quantitative inter-model comparisons to allow for a better understanding of the applicability of existing and new methodologies to different scopes, sectors, and applications.…”

“…While there is no way to truly map all of the interactions between physical, ecological, biological, economic, social, and other systems, the essence of nexus studies is to try and capture the relevant trade-offs and feedbacks that may influence their outcomes. Several nexus review papers (Endo et al, 2017;Dai et al, 2018;Newell et al, 2019;Tashtoush et al, 2019;Abdi et al, 2020;Stylianopoulou et al, 2020;Purwanto et al, 2021;Vinca et al, 2021) show that existing nexus methodologies are unable to equally or appropriately weigh the different systems considered, because there is a lack of data, a lack of knowledge, or a lack of interest. Caution should be taken not to draw system boundaries arbitrarily or out of convenience simply to address methodological or data-availability constraints.…”

Trade-Offs in the Water-Energy-Ecosystem Nexus for Cascade Hydropower Systems: A Case Study of the Yalong River, China

“…The water-energy -ecosystem nexus (WEEN) is a focus of much research (Kuriqi et al, 2020;Vinca et al, 2021;Yadav et al, 2021). Hydropower is an important part of WEEN, which is interconnected and interdependent with other sectors of the nexus (Zhang et al, 2018b).…”