Network Utility Analysis: A Non-Thermodynamic Constraint to Trophic Transfer Efficiency

The efficiency of resource transfer between trophic levels in an ecosystem tend to be relatively low in spite of the considerable amount of time organisms have had to evolve uptake and assimilation processes. In fact, a general rule of thumb in ecology is that only about 10 percent of the total energy intake into an organism is transferred up to the next trophic level. In addition to the thermodynamic, physical, and chemical limitations, our research indicates another possible limitation to trophic transfer efficiency. Utility analysis, a resource-based input-output measure of the overall usefulness a component's flow has on the entire system, is used to identify the qualitative and the quantitative relations in a model. For simple systems, utility is dependent on transfer efficiencies, and in more complex models with feedback and cycling, the relative net transfer efficiency is used. For utility to be calculable, the matrix of direct utility must meet a convergent criterion. However, when these efficiencies are too large this criterion is not met. This is interpreted to mean that utility, which is inherently positive, is not conveyed within these systems. This paper shows, for simple food chain models, where the breakdown in utility analysis occurs and what patterns exist as systems approach this threshold. Although computable utility may not be a necessary condition for low trophic efficiency, it may be sufficient to explain low transfer efficiencies in in constituted ecosystems

Systems ecology, energy networks, and a path to sustainability

One of the great advances of the 20th century was the rise of a formal systems science and systems thinking. This progress influenced ecology in ways that provided new insight to the structure and function of ecosystems using tools from thermodynamics, networks, information theory, and more. We have been able to increase our understanding of how ecosystems function in terms of using available energy to create complex structures to move away from thermodynamic equilibrium and how these self-organizing structures adapt to changing situations. Ecological goal functions can measure this orientation of ecosystem growth and development (EGD). This presentation addresses how these metrics attuned for ecosystems have relevant application in socio-economic systems. In particular, energy network science is a new paradigm that draws from thermodynamics, information theory, and network analysis to assess the organization, patterns, and dynamics of diverse systems such as ecosystems, financial systems, and urban metabolism. Our understanding of sustainable systems is informed by knowing how ecological and other far-from-thermodynamic equilibrium systems create, maintain, and sustain their functional activities. This approach builds from the seminal efforts of systems thinkers such as Gregory Bateson, Buzz Holling, Jane Jacobs, Sven Jørgensen, Donella Meadows, Jacob Moreno, Bernard Patten, Joseph Tainter, Robert Ulanowicz, and Ilya Prigogine

Overview of Network Environ Analysis: A systems analysis technique for understanding complex ecological systems

Network Environ Analysis, based on network theory, reveals the quantitative and qualitative relations between ecological objects interacting with each other in a system. The primary result from the method provides input and output .environs., which are internal partitions of the objects within system flows. In addition, application of Network Environ Analysis on empirical datasets and ecosystem models has revealed several important and unexpected results that have been identified and summarized in the literature as network environ properties. Network Environ Analysis requires data including the intercompartmental flows, compartmental storages, and boundary input and output flows. Software is available to perform this analysis. This article reviews the theoretical underpinning of the analysis and briefly introduces some the main properties such as indirect effects ratio, network homogenization, and network mutualism. References for further reading are provided

Analysis of Indirect Effects in a Hydrologic Model for Use in Determining Potential Primary Productivity

A current program of the Land-Use and Land-Cover Change (LUC) at the International Institute for Applied Systems Analysis is to determine the potential primary productivity of agricultural crops for parts of China, the former Soviet Union, and Mongolia. The work in this paper, supported by the Dynamic Systems group, is in collaboration with that LUC program. The main goal is to provide a methodology for investigating some of the indirect processes and pathways which affect primary productivity of crop production and to introduce a different modeling approach in estimating the potential productivity. The three main objectives of this research are the following: 1. Use network analysis to identify and quantify the indirect processes that affect the primary production of crop growth, 2. Develop a flow-storage compartment model to be used in the network analysis, 3. Quantify the flow-storage model using a dynamical simulation model. Although many factors control the primary productivity of a region, a main one is the availability of water, so the simulation model used here is based on the hydrologic budget of the study region. A four-compartment hydrologic model is developed which includes the within-system transfers between ground water, surface water, atmosphere, and vegetation, along with the external water transfers with the environment. When available, on-site climatic data are used to evaluate the model's parameters. The model is applied to a homogeneous region with a single cover type. Specifically, the model is calibrated using data from the Kursk region of Russia and the crop barley. This research shows that the atmosphere and soil moisture content both contribute important direct and indirect pathways for the water to reach the vegetation and subsequently affect primary production. Also, based on this model, the primary productivity is most sensitive to the vegetation growth rate and the rate of evapotranspiration. The model rationale and the results are discussed herein

Measurement and Spatial Distribution of Urban Land Use Compactness in Chaoyang District of Beijing, China

China is in the process of rapid urbanization, and wise land use is critical to the long-term sustainbility of Chinese cities. Promotion of a compact city is typically believed to be a helpful for sustainable land use management. However, given the fact that Chinese cities are characterized by high population densities, the applicability of a more compact solution to expanding cities in China remains questionable; there is little evidence to suppot the many claims in its favor. In seeking to provide empirical data to explore the application of compact city theory in China, one of the key problems researchers face is the task of measuring the urban compactness, in order to objectively investigate the current characteristics of urban compactness. To meet this need, indices were developed for measuring the urban land use compactness, by which the partial distribution characteristics of urban land use compactness were identified and applied to the Chaoyang district of Beijing. The following conclusion can be made: (1) Comprehensive land use compactness in Chaoyang district has increased during the period 2001-2007, especially the population density; (2) the spatial distribution of land use compactness has the characteristics of a ring structure, which shows a decreasing trend with its distance to the city center; (3) there is a strong positive correlation between urban land use compactness and location. The better the location is, the higher the land use compactness is

Core network compartments: Relative importance of ecosystems players in moving energy through the system

Ecosystems that are depicted as nodes (species groups) and links (trophic transfers) encompass well defined roles in terms of their trophic structure. Some are primary producers and furnish the system with newly bound energy or nutrients, whereas others divide themselves over various trophic levels creating a hierarchy of energy use and reuse. All waste and mortality products of nodes comprise the non-living environment of ecosystems, often supporting a considerable part of the system as detritus. All food sources are in general used, but are so to variable extents. Some links are always among the major links, e.g. flows from detritus or remineralisation from bacteria. Similarly, flows into and from high turnover nodes, which are either small species with high turnover rates, or those with disproportional high standing stock play an important role in shunting energy through the system. Ecosystem indices calculated from weighted ecological networks describing the patterns of energy flow through an ecosystem are often applied to empirical data in order to categorise the system as an efficient or inefficient energy user. We calculated flow diversity (as Shannon's Index) and average mutual information (AMI, as the degree of flow constraint) according to the method of Ulanowicz (1986). Special attention was given to the contribution of each system part to the overall holistic property. A comparison of several, mainly estuarine, ecosystems, shows that it is mostly flows involving the same species groups contributing to the bulk to the index value. These were flows from detritus, bacteria, and primary producers. The relative importance of flows from heterotrophic groups (e.g., species and species groups of macrozoobenthos, meiofauna, zooplankton, fish) compared to that of the "main" groups was comparatively minor

Exploring Simple Structural Configurations for Optimal Network Mutualism

Energy flow is a primary organizing principle in ecological systems, and therefore various aspects of this have been proposed as ecological goal functions [8, 5]. One such goal function considers that the integral utility (direct + indirect) will tend to be positive in well-developed systems [3, 4, 10]. In this research, we investigate several basic network structures to determine the specifc relationship types between compartments and identify those structures that lead to greater quantitative and qualitative utility. This research contributes to the overall discipline of ecological network analysis

Constructing a Network of the Social-economic Consumption System of China Using Extended Energy Analysis

The prominent conflict between consumption and environmental resources is acknowledged as a significant force in affecting the social-ecological community balance. The whole process of resource allocation, utilization, efficiency and outcome are crucial clues in uncovering the structural and functional characteristics in complex consuming systems. Herein, networks provide a systems-oriented modelling technique for examining the structure as well as the flow of materials or energy from an input-output perspective. Meanwhile, extended exergy, the only currently available thermodynamic based metric for social-economic environmental impacts associated with energy consumption, manpower, and monetary operation as well as environmental emission, is an extension of the labor theory of value and a possible sustainability metric. The core purpose of this research is to construct a network of the consumption system of China using extended exergy analysis to explain the interrelationship among different sectors within a thermodynamic metric. Therefore, we first make a database of Chinese consumption using extended exergy accounting. Data are available for 2007, which can be divided into seven sectors based on the reclassification of the regularly published 42-sector Input-Output Table, namely, (1) Agriculture, (2) Extraction, (3) Conversion, (4) Industry, (5) Transportation, (6) Tertiary, and (7) Domestic sectors. Then we construct an extended exergy network to gain insight into the thermodynamic distribution within sectoral criterion. Lastly, the network results explain how China's social metabolism is maintained by a large quantity of energy, resources, and labor

Cyclic energy pathways in ecological food webs

Standard ecology textbooks typically maintain that nutrients cycle, but energy flows in unidirectional chains. However, here we use a new metric that allows for the identification and quantification of cyclic energy pathways. Some of these important pathways occur due to the contribution of dead organic matter to detrital pools and those organisms that feed on them, reintroducing some of that energy back into the food web. Recognition of these cyclic energy pathways profoundly impacts many aspects of ecology such as trophic levels, control, and the importance of indirect effects. Network analysis, specifically the maximum eigenvalue of the connectance matrix, is used to identify both the presence and strength of these structural cycles

Assessing the environmental impacts of urban growth using land use/land cover, water quality and health indicators: A case study of Arequipa, Peru

Problem statement: This research assesses the direct effects of urban expansion on land cover/use, river flow, water quality and the indirect effects of these variables in the rate of gastrointestinal disease in people in Arequipa, Peru through the combined use of satellite remote sensing and geographic information systems. Approach: It also uses information about demographic changes, hydrologic data and land cover change in the Arequipa region for the last 17 years. The goal is to understand the relationship between urbanization, water quality in the Chili River and incidence of gastrointestinal diseases. Results: Landsat imagery was used to determine this relationship and to extrapolate business as usual trends into the future ten years from now. Results indicate that there has been notable urban growth and a loss in volcanic material land and cropland between 1990 and 2007, as new urban developments have appeared in these areas. The population expansion over volcanically active area is particularly troubling since it poses a potential human health risk. We also model a business as usual scenario out to the year 2020, which shows continued loss of these land use types and serves as a warning for land managers to consider alternate policies. Conclusion/Recommendations: The analysis also shows a direct correlation between urbanization with the decrease of water quality and the increase in the incidence of gastrointestinal diseases