Analyzing the role of indirect connections in empirical networks

Advanced System Analysis (ASA) Program researchers develop methods and case studies analyzing empirical networked systems from the ecological to the economic, financial, energy-related, and others. They also analyze the latest big data sets on social networks.

© Lublubachka | Dreamstime

© Lublubachka | Dreamstime

Systems ecology aims to study ecological systems in a holistic fashion. In this vein, food webs are treated as networks of nodes—species or functional groups—interacting with each other by means of predation. To analyze this, network analysis methods for quantifying the effects of both direct and indirect (i.e., those involving intermediate nodes) interactions in ecological networks have been developed. Based on analyses of systems flows, these methods can reveal ecological relationships among system components.

ASA researched further applications of network analysis to study the vulnerability of food webs with respect to anthropogenic stresses. Introducing a network perspective in this way can yield insights regarding a more sustainable way of managing natural systems. For instance, ASA researchers were able to assess the environmental impact of dam construction on the food web of the upper Mekong River, China, and evaluate effects of multiple stressors after damming (i.e., sedimentation, discharge change, and heavy metal pollution) in terms of its direct and indirect impacts and also across species [1]. A further ASA study employed the robustness definition as a trade-off between system efficiency and redundancy, suggested in the systems ecology literature, to examine the food web of the Mdloti estuarine system, South Africa, under anthropogenic stresses of eutrophication and overfishing [2].

Inspired by the power of network ecology, ASA is exploring the potential of transferring it to various other applications. Results published in 2015 include: measuring network diversity and resilience of the national electricity trade systems [3] and global commodity trade networks [4]; exploring symbiosis of the industrial system in Shandong Lubei eco-industrial park, China, by analyzing the production-related sulfur flows [5]; evaluating urban metabolism of air, water, and land pollution flows [6][7][8].


[1] Chen S, Chen B & Fath BD (2015): Assessing the cumulative environmental impact of hydropower construction on river systems based on energy network model. Renewable and Sustainable Energy Reviews 42:78-92.

[2] Mukherjee J, Scharler UM, Fath BD & Ray S (2015): Measuring sensitivity of robustness and network indices for an estuarine food web model under perturbations. Ecological Modelling 306:160-173.

[3] Kharrazi A, Sato M, Yarime M, Nakayama H, Yu Y & Kraines S (2015a): Examining the resilience of national energy systems: Measurements of diversity in production-based and consumption-based electricity in the globalization of trade networks. Energy Policy 87:455-464.

[4] Kharrazi A, Kraines A, Rovenskaya E, Iwata & Yarime M (2015b): Examining the Ecology of Commodity Trade Networks using an Ecological Information-Based Approach: Towards Strategic Assessment of Resilience. Journal of Industrial Ecology 19(5):805-813.

[5] Zhang Y, Zheng H & Fath BD (2015a): Ecological network analysis of an industrial symbiosis system: A case study of the Shandong Lubei eco-industrial park. Ecological Modelling 306:174-184.

[6] Yang S, Chen B, Fath BD (2015): Trans-boundary total suspended particulate matter (TSPM) in urban ecosystems. Ecological Modelling 318:59-63.

[7] Zhang Y, Li J, Fath BD, Zheng H, Xia L (2015b): Analysis of urban carbon metabolic processes and a description of sectoral characteristics: A case study of Beijing. Ecological Modelling 316 (7651):144-154.

[8] Yu Y, Ren H, Kharrazi A, Ma T, Zhu B (2015): Exploring socioeconomic drivers of environmental pressure on the city level: The case study of Chongqing in China. Ecological Economics 118:123-131. 


Beijing Normal University, China

Tsinghua University, China

Tokyo University, Japan

University of KwaZulu-Natal, South Africa 

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Last edited: 15 March 2016


Brian Fath

YSSP Scientific Coordinator Capacity Development and Academic Training Unit

Principal Research Scholar Systemic Risk and Resilience Research Group - Advancing Systems Analysis Program

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International Institute for Applied Systems Analysis (IIASA)
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