Diversity–stability relationships revisited: scaling rules for biological communities near equilibrium

The debate on diversity–stability relationships has a long history of theoretical interest and plays a central role in development of modern ecology. But such debate has recently re-opened under critical scrutiny both in theoretical and empirical studies. In this paper we use allometric (or energetic) scaling and statistical physics approaches to this problem. On the basis of local Damuth symmetry, a Markov model of transfer of energy between different species, and the fluctuation–dissipation theorem, scaling rules of species number and population variability of biological communities near equilibrium are derived. These scaling rules indicate that the diversity–stability relationship may be an energetic and thermodynamic consequence of ecological systems near equilibrium, not a simple statistical consequence as derived by other recent theoretical work.     

Defining an ecological thermodynamics using discrete simulation approaches

New insights into interdisciplinary engineering endeavors, from classical modeling to nano–macroscale extrapolation and critical evaluation, weigh heavily on the pervasive nature of thermodynamics in the physical world. Just as statistical thermodynamic approaches provide a beneficial complement to a process-based macroscale thermodynamic approaches with physical systems, a Lagrangian approach to energetics in biological systems can, we believe, provide a beneficial complement to popular Eulerian approaches. Statistical thermodynamics is used as a springboard for some analogies that are similarly used to leap into the ecological scale. The Lagrangian simulation, a discrete simulation, is implemented with a spreadsheet approach, a discrete simulation approach, and a new stochastic differential equation solution approach. The Lagrangian approach complements the more widely used continuous (or Eulerian) simulation approaches such as STELLA or Environ theory approaches. The Lagrangian approach decomposes energy into small packets or ecological quanta. An ecological entropy is computed based on nodal contacts in the network, with the notion that nodal contact is analogous to molecular speed. In the cases shown, the results of ecological entropy appear generally consistent with thermodynamic entropy. A newly available simulation package (ECONET) enabled an easy Lagrangian approach to analyzing the Cone Springs and Oyster ecological models. An analogy between nodal contact numbers and molecular speed was developed to enable computation of an ecological entropy. There is a similarity between classical and ecological entropy based on similarity in shape of the Maxwell–Boltzmann distributions to the packet-nodal contact numbers. An ecological temperature can be defined based on this similarity. Selected ratios of ecological entropy versus classical macroscopic entropy appeared to have some degree of robustness. Other aspects of ecological thermodynamics remain to be developed. It is felt that the ecological thermodynamics approach presented offers an improved way to combine biochemical and ecological entropy. A sound combination of entropies at multiple scales will help bring together measurements at disparate scales.     

Resilienz vs. Effizienz – ein kritischer Blick auf die Umweltökonomie

Background, aim, and scope Economists assess politics (also concerning energy supply) due to the efficiency criterion. Thus, economic instruments for environmental protection shall contribute to achieve ecological goals in an (cost-)efficient way. We show that the overemphasis of efficiency is an alien in the way (ecological) systems are working. Mostly, ecological systems are not high-grade efficient. Hence, economic instruments of environmental protection introduce an inappropriate logic to ecological systems that may have severe impacts on their resilience. We illustrate this with the example of emission trading. Time efficiency is considered to be a powerful criterion due to the interest yield requirements of investors, also for ecological investments. We show how the concentration on time efficiency destroys diversity and has negative impacts on the resilience of (eco-)systems. Main features The economic system is embedded in society and natural environment (as self-organizing, living systems). The economy as an ‘instrumental system’ should serve these systems. The guiding value approach (a system theory approach) gives indication that overemphasizing certain guiding values (such as efficiency, as the economic science does) may weaken the functional capability of systems and finally may lead to a collapse of the systems. Results and discussion The article tries to change the focus of the discussion. An altered focus probably has to be implemented by scientists of other subject areas. Contemporary environmental economics (with its focus on efficiency) is unable to give satisfying answers on the pestering problems. Conclusions Criticising the primacy of efficiency is not the same as generally to disclaim considering efficiency needs. Instead, based on the guiding value theory, we want to be contrary to the one-sided and dominating stressing of the of the efficiency criterion. Perspectives Not following the efficiency guide any more means to think over some ‘sacred cows’ such as emission trading or shareholder value. Instead we have to think over alternative designs to reach the ecological targets.     

Control system approaches to ecological systems analysis: Invariants and frequency response

The steady-state assumption is a mainstay for the analysis of ecological systems with more than three or four states. However, it is well accepted in ecology that inputs to large systems come in pulses assumed to have a reasonably constant magnitude and frequency. Steady pulse inputs and the use of electro-chemical–mechanical control systems methodology enables limited short term dynamic responses of ecological systems of a scale often occurring in systems of potential engineering importance to be analyzed. This paper explores and presents a survey of multi-input–multi-output (MIMO) control systems analysis of ecosystem network models to better understand pulse frequency issues and further develop experimentally verifiable approaches to testing the MIMO concept. The analysis process is demonstrated using two network model exemplars. Two aspects of MIMO analyses appear relevant to understanding ecological systems: (1) Eigenvalue invariant analyses and singular value decomposition (SVD) analyses enable assessment of stability and relative strength of states. Eigenvalues reflect time constants and provide a check on experimentally determined system matrices. (2) Analysis of SVD versus frequency for each output indicates maximum pulse frequencies that allow system components to benefit from pulsing. As a group, MIMO analyses complement other analytical methods and provide a theoretical systems focus convenient for analyzing ecosystems from an engineering perspective.     

Assessing self-organization of plant communities—A thermodynamic approach

Thermodynamics is a powerful tool for the study of system development and has the potential to be applied to studies of ecological complexity. Here, we develop a set of thermodynamic indicators including energy capture and energy dissipation to quantify plant community self-organization. The study ecosystems included a tropical seasonal rainforest, an artificial tropical rainforest, a rubber plantation, and two Chromolaena odorata (L.) R.M. King & H. Robinson communities aged 13 years and 1 year. The communities represent a complexity transect from primary vegetation, to transitional community, economic plantation, and fallows and are typical for Xishuangbanna, southwestern China. The indicators of ecosystem self-organization are sensitive to plant community type and seasonality, and demonstrate that the tropical seasonal rainforest is highly self-organized and plays an important role in local environmental stability via the land surface thermal regulation. The rubber plantation is at a very low level of self-organization as quantified by the thermodynamic indicators, especially during the dry season. The expansion of the area of rubber plantation and shrinkage of tropical seasonal rainforest would likely induce local surface warming and a larger daily temperature range.     

Exergetic assessment for ecological economic system: Chinese agriculture

Based on the thermodynamic concept of exergy as a unified measure for environmental resources and economic products, a framework for systems assessment is presented for ecological economies. With a typical systems diagram devised for a general ecological economy with four arm fluxes for free local natural resources, purchased economic investment, environmental impact and economic yield, system indices of the renewability index, exergy yield ratio, exergy investment ratio, environmental resource to yield ratio, system transformity and environmental stress index are defined for a congregated systems ecological assessment with essential implications to sustainability. As a detailed case study to the Chinese agriculture from 1980 to 2000 with cropping, forestry, stockbreeding and fishery sectors, extensive exergy account and systems assessment are carried out with emphasis on annual and structural variations against social political transitions. For the overall agriculture as a congregated ecological stage, the value of the system transformity is found around 10, the typical value for the general ecological hierarchy as well devised by Odum associated with Lindeman's Tenth Law.     

三峡库区生态安全问题与对策

具体分析了三峡库区自然、社会和经济三方面的生态安全问题。采用相对资源承载力的研究思路与计算方法，得出该地区超载人口占该地区总人口的比例达37．4％，人地矛盾日益突出的结论。针对三峡库区的生态安全问题，提出了如下的对策：建立科学合理的生态补偿机制和库区立体管理模式；建立库区生态安全预警系统和绿色GDP核算体系；倡导各产业在生态安全下的生产经营运行模式；建立库区县市级管理责任定位体制，明确不同部门、地区所对应的库区生态流域单元的管理权限和责任：积极引导公众进行安全生产和科技减灾。     

Examining the colonization process of exotic species varying in competitive abilities using a cellular automaton model

Current threats of invasive species have significant implications for ecological systems. Given their potential impacts, invasive species have been the subject of extensive empirical and theoretical studies. However, these studies have tended to focus on species that produce highly visible ecological and economic impacts. In our study, we take a step back from focusing on these high-impact invasive species, and examine the general colonization (invasion) process of exotic species that have various “competitive abilities” against the native species. Using a two-species cellular automaton model, we demonstrate that: (1) a threshold level of competitive ability is required for the exotic species to successfully establish in a new landscape and (2) an exotic species with superior competitive ability does not necessarily become dominant in a landscape (alternatively, a species that has inferior competitive ability may successfully colonize a new system). Our findings have significant implications for the study of species invasions and also provide clues to how species assemble in ecological communities.     

Ecological network determination of sectoral linkages, utility relations and structural characteristics on urban ecological economic system

Analyzing the structure and functioning of the urban system revealed ways to optimize its structure by adjusting the relationships among compartments, thereby demonstrating how ecological network analysis can be used in urban system research. Based on the account of the extended exergy utilization in the sector of urban socio-economic system, which is considered as the composition of extraction (Ex), conversion (Co), agriculture (Ag), industry (In), transportation (Tr), tertiary (Te) and households (Do) sectors, an urban ecological network model is constructed to gain insights into the economic processes oriented to sustainable urban development. Taking Beijing city as the case, the network accounting and related ecological evaluation of a practical urban economy are carried out in this study in the light of flux, efficiency, utility and structure analysis. The results showed that a large quantity of energy and resources have to be consumed to maintain the structure and function of a city. The thermodynamic efficiencies of individual sector in Beijing remain at a low level. The social system in Beijing is a highly competitive network, and there are 8 competitive relations and only two mutualistic ones. The Domestic and Agricultural sector are the major controlling factors of the system. Moreover, the assessment results of Beijing are compared with the other three socio-economic systems, Norway, UK and Italy, and the ecological network function and structure comparisons are correspondingly illuminated and discussed. The conclusions indicate that the exergy-based network analysis can be refined to become an integrative tool for evaluation, policy-making and regulation for urban socio-economic system management concerning structure and efficiency at urban levels.     

Progress in global ecological modelling

The development of ecological modelling on global level since the middle of the 19th century is first reviewed, including application of statistical analysis, introduction of logistic curve, earth surface modeling, systems ecology, computer-oriented mathematical models and spatially explicit models. Finally, we discuss problems existing in ecological modelling on global level.     

Matter accumulation and energy expenditure in planktonic ecosystems at different trophic levels

Functional peculiarities of pelagic communities from temperate and tropical zones of the ocean have been investigated in terms of food-web interrelations and balance sheets of matter and energy of the major populations and ecological groupings. Ranging from temperate or epiplankton ecosystems to tropical oceanic or deepwater ones, as well as from upwelling zones to stable oceanic oligotrophic regions, the following regular changes in the communities' main functional indices have been established: (1) enlargement of the food spectrum, omnivorousness and predatory activity; (2) reduction of rations and rates of organic matter accumulation in the lower heterotrophic levels with simultaneous increase of energy expenditure; (3) increased trophic complexity and stability of communities. Epiplanktonic systems of low stability proved to be richer and commercially more profitable.     

State-of-the-art of ecological modelling with emphasis on development of structural dynamic models

The paper deals with two major problems in ecological modelling today, namely how to get reliable parameters? and how to build ecosystem properties into our models? The use of new mathematical tools to answer these questions is mentioned briefly, but the main focus of the paper is on development of structural dynamic models which are models using goal functions to reflect a current change of the properties of the biological components in the models. These changes of the properties are due to the enormous adaptability of the biological components to the prevailing conditions. All species in an ecosystem attempt to obtain most biomass, i.e. to move as far away as possible from thermodynamic equilibrium which can be measured by the thermodynamic concept exergy. Consequently, exergy has been proposed as a goal function in ecological models with dynamic structure, meaning currently changed properties of the biological components and in model language currently changed parameters. An equation to compute an exergy index of a model is presented. The theoretical considerations leading to this equation are not presented here but references to literature where the basis theory can be found are given. Two case studies of structural dynamic modelling are presented: a shallow lake where the structural dynamic changes have been determined before the model was developed, and the application of biomanipulation in lake management, where the structural dynamic changes are generally known. Moreover. it is also discussed how the same idea of using exergy as a goal function in ecological modelling may be applied to facilitate the estimation of parameters.     

An ecological framework for contextualizing carnivore–livestock conflict

Carnivore predation on livestock is a complex management and policy challenge, yet it is also intrinsically an ecological interaction between predators and prey. Human–wildlife interactions occur in socioecological systems in which human and environmental processes are closely linked. However, underlying human–wildlife conflict and key to unpacking its complexity are concrete and identifiable ecological mechanisms that lead to predation events. To better understand how ecological theory accords with interactions between wild predators and domestic prey, we developed a framework to describe ecological drivers of predation on livestock. We based this framework on foundational ecological theory and current research on interactions between predators and domestic prey. We used this framework to examine ecological mechanisms (e.g., density-mediated effects, behaviorally mediated effects, and optimal foraging theory) through which specific management interventions operate, and we analyzed the ecological determinants of failure and success of management interventions in 3 case studies: snow leopards (Panthera uncia), wolves (Canis lupus), and cougars (Puma concolor). The varied, context-dependent successes and failures of the management interventions in these case studies demonstrated the utility of using an ecological framework to ground research and management of carnivore–livestock conflict. Mitigation of human–wildlife conflict appears to require an understanding of how fundamental ecological theories work within domestic predator–prey systems.     

Representing general theoretical concepts in structural equation models: the role of composite variables

Structural equation modeling (SEM) holds the promise of providing natural scientists the capacity to evaluate complex multivariate hypotheses about ecological systems. Building on its predecessors, path analysis and factor analysis, SEM allows for the incorporation of both observed and unobserved (latent) variables into theoretically-based probabilistic models. In this paper we discuss the interface between theory and data in SEM and the use of an additional variable type, the composite. In simple terms, composite variables specify the influences of collections of other variables and can be helpful in modeling heterogeneous concepts of the sort commonly of interest to ecologists. While long recognized as a potentially important element of SEM, composite variables have received very limited use, in part because of a lack of theoretical consideration, but also because of difficulties that arise in parameter estimation when using conventional solution procedures. In this paper we present a framework for discussing composites and demonstrate how the use of partially-reduced-form models can help to overcome some of the parameter estimation and evaluation problems associated with models containing composites. Diagnostic procedures for evaluating the most appropriate and effective use of composites are illustrated with an example from the ecological literature. It is argued that an ability to incorporate composite variables into structural equation models may be particularly valuable in the study of natural systems, where concepts are frequently multifaceted and the influence of suites of variables are often of interest.     

Multicriteria analysis applied to the sustainable agriculture problem

SUMMARY

The aim of this paper is to present an operational approach to compare the relative sustainability of existing farming systems. Sustainability rests on the assumption that an equilibrium must exist among three domains: social, economic and ecological. If we are to look for a solution to the problem, we must face a multi-dimensional approach. We propose that multicriteria analysis, a multi-dimensional method, is an appropriate methodology to study the issue. As sustainability cannot be measured directly, the way out is to use indicators. We have performed a thorough analysis of four farming systems existing in Guaíra, SP, Brazil to validate the methodology. Thirty indicators of sustainability (ten ecological, ten social, and ten economic) were defined and used to perform the analysis. The results of the multicriteria analysis proved useful because of its capability of reducing the dimensionality of the problem. From the three dimensions of sustainability, a final score was derived that can easily compare the relative sustainability of each farming system.     

The problem of ecosystem stability and some applications of one of the stochastic methods in investigation of this problem

This paper describes some possible applications of one of the stochastic methods which may be used in ecological studies. The role of stochastic methods in investigations of the dynamics of ecosystems is gaining in importance. Stochastic methods are very useful for investigating the stability of ecosystems and the criteria of stability of natural systems, especially where the influence of permanent small-scale random disturbances has been noticed. Some criteria have been suggested and examples of use of these criteria are given.     

Socio-environmental co-evolution: some ideas for an analytical approach

A number of scholars, mainly in ecological economics, have been attracted to the concept of co-evolution for the analysis of socio-environmental change. Yet none has adopted and developed an applied analytical approach using an explicitly evolutionary framework. This paper discusses how other scholars in economics, technological studies, organization and political science have been using evolutionary explanations and draws some lessons for ecological economics. Evolutionary is a mode of explanation based on the selective retention of renewable variation. It accounts for phenomena of structural fit and change in a variety of domains. A co-evolutionary explanation, by extension, entails two or more evolving systems whose interaction affects their evolution. Socio-environmental co-evolution involves human systems (material practices and non-material ideas and values) and non-human systems (living and physical). The challenge then is how to develop case-specific, empirical applications that define and elaborate the variants that co-evolve and specify the processes of mutual selection. Applications could benefit from existing classifications and causal propositions in the natural and social sciences. Co-evolution is part of a larger analytical toolkit for looking at complex socio-environmental problems. Although distinct, there are strong synergies, complementarities and potential for combined uses between co-evolutionary, co-dynamic and complexity-based explanations.     

Transport,distribution and toxic effects of polychlorinated biphenyls in ecosystems: Review

Investigation of various aspects of the ecological problems of polychlorinated biphenyls (PCBs) has grown and continues to grow with remarkable intensity. However, it appears that certain areas of PCBs research are developed further than the others. For example, chemical and physical behavior and synthesis of PCBs are well studied, while the metabolism of PCBs and other routes of degradation, including toxicological significance and environmental impact, continue to challenge the scientists.In this paper, the chemical and physical properties of PCBs as well as the implications of these properties for the behavior of PCBs in ecological systems are discussed. The effect of PCBs on interrelated ecological systems are described. The distribution and fate of PCBs in the atmosphere, hydrosphere and lithosphere, and transport of PCBs through these systems are discussed. The toxic significance, biological accumulation and ecological magnification are described at various trophic levels.     

Tetracycline antibiotics in the environment: a review

Tetracycline antibiotics are one of the primarily antibiotics groups used for veterinary purposes, for human therapy and for agricultural purposes. Amongst the different antibiotics used, more attention is paid to tetracycline’s as it exhibits serious environmental problems including ecological risks and human health damages. Due to their extensive usage, most of the actual evidence suggests that tetracycline antibiotics are omnipresent compounds found in different ecological compartments. After medication, more than 70 % of tetracycline antibiotics are excreted and released in active form into the environment via urine and feces from humans and animals. Their highly hydrophilic character and low volatility have resulted in significant persistence in the aquatic environment. Very few studies describe the fate and toxicity of tetracycline antibiotics in the environment. Here, we review several important issues with regard to: (1) the toxicity of these compounds on aquatic and terrestrial organisms; (2) their estrogenic effects; (3) their behavior in different ecological systems and; (4) the by-products generated during water treatment. These antibiotics residues promote the development of antibiotic resistant microorganisms, which can induce adverse effect to human health by increasing the risk of certain infections. Based on recent research results, the occurrence of tetracycline antibiotics in the environment inhibits the growth of some terrestrial and aquatic species. Besides, the residual concentrations of such drugs could affect steroidogenic pathway and consequently may cause endocrine disruption of aquatic species. Most of the wastewater treatment plants are not capable of removing effectively the tetracycline antibiotics. Therefore, there is a need to develop alternative processes to remove them from waters. Advanced oxidation processes have been proposed as alternative methods to ensure higher degradation and mineralization of tetracycline antibiotics are present in waters.