Principle of the worst scenario in the modelling past and future of biosphere dynamics

The “biosphere–climate” system is subjected to different influences (influx of anthropogenic CO₂ and pollutants, deforestation, harmful land management, biological species depopulation, etc.). Therefore, the vital question arises: “Can these influences lead to irreversible negative changes in the climate–biosphere system or a global ecological catastrophe?” The possibility of irreversible changes may be not very high, but one cannot ignore it. So the main aim of our investigation is to evaluate possible consequences of human impact on the biosphere focusing on irreversible changes of it.     

The model of long-term evolution of the carbon cycle

The weathering processes and their role in the formation of the atmospheric carbon and, as a consequence, on the climate are considered. The model operates in the framework of “active planetary cover”, i.e. considering the interactive role of the biosphere, looking at its development as a non-linear evolutionary system of so-called “virtual biospheres”.     

What did Lotka really say? A critical reassessment of the “maximum power principle”

This paper presents a critical discussion of the so-called “maximum power principle”, often quoted in studies about the energy balance of living systems and also known in the emergy literature as “maximum em-power principle”. Several authors consider this principle highly relevant and some even proposed it as a “fourth law of thermodynamics”. A critical analysis of the original source, namely Alfred Lotka's 1921-22 papers, conducted both in an historical perspective (the connection between Lotka's writings and the ongoing debate at his time) and in a more modern context, leads to a more detailed and less biased assessment. It turns out that in spite of Lotka's very anticipatory and incredibly sharp vision of the possible interconnections between the second law of thermodynamics and evolutionism, doubts arise about the general applicability of his “maximum power principle”. From an accurate analysis of his writings, it can be concluded that: (a) Lotka explicitly and consistently addressed the “optimal use” of the flow of exergy (available energy), and therefore the quantity defined as “em-power” is an incorrect interpretation of Lotka's constrained maximum power principle; (b) “Lotka's principle” can be reformulated within Ziegler's “maximum entropy production” or Prigogine “minimum entropy generation” paradigm only under two different respective sets of rather stringent additional conditions which Lotka was probably already aware of but never explicitly stated.     

Incomplete Information and Incentives to Free Ride on International Environmental Resources

This paper studies free-riding incentives on common environmental resources in an incomplete information repeated game where abatements are perishable and perfect substitutes. Two contrasting types of perfect Bayesian equilibria emerge: For high discount factors, or low discount factors but “pessimistic” prior beliefs, the inclusion of incomplete information has no impact on the pattern of abatements. Otherwise the countries attempt to use their private information strategically and the game becomes a war of attrition. This generates an outcome where the “pessimistic” country unilaterally abates forever, and another which involves delay until the first abatement if both countries are “optimistic”.     

Dynamic compartment approach for modelling regimes of carbon cycle functioning in bog ecosystems

Svirezhev's method of dynamic model design by a given “storage-flow” diagram [Svirezhev Y.M., 1997. On some general properties of trophic networks. Ecol. Model. 99, 7–17] is developed and used for investigating dynamic regimes of carbon cycle functioning in a typical boreal transitional bog ecosystem. Ecosystems are often represented by static “storage-flow” diagrams reflecting their structure and matter or energy transfer between components at fixed time moments. Using the data of such diagrams aggregated in ecological field studies one can construct a dynamic model of the ecosystem to predict its future behaviour and to estimate a response to external perturbations—natural and human. Stability of both current equilibrium and possible alternative steady states and more complicated attractors are studied under two types of parameter perturbation: CO₂ atmospheric concentration increase initiated by greenhouse effect, and change in the rate of carbon output from dead organic matter and litter which depends on the water table level and possible peat excavation. Calculation of bifurcation curves gives areas in the parameter space where stable functioning of carbon cycle is provided. Steady states can be interpreted as raised bog, meadow, forest and fen. CO₂ concentration increase leads the current state of transitional bog to loose stability with appearance of oscillatory dynamics and further evolution to the chaotic attractor. The model is rich by chaotic solutions serving as transition regimes between regular steady and periodic attractors. Another chaotic regime is formed from forest equilibrium and exists in the same area of phase space where current equilibrium is stable.     

Using accelerometer,high sample rate GPS and magnetometer data to develop a cattle movement and behaviour model

The study described in this paper developed a model of animal movement, which explicitly recognised each individual as the central unit of measure. The model was developed by learning from a real dataset that measured and calculated, for individual cows in a herd, their linear and angular positions and directional and angular speeds. Two learning algorithms were implemented: a Hidden Markov model (HMM) and a long-term prediction algorithm. It is shown that a HMM can be used to describe the animal's movement and state transition behaviour within several “stay” areas where cows remained for long periods. Model parameters were estimated for hidden behaviour states such as relocating, foraging and bedding. For cows’ movement between the “stay” areas a long-term prediction algorithm was implemented. By combining these two algorithms it was possible to develop a successful model, which achieved similar results to the animal behaviour data collected. This modelling methodology could easily be applied to interactions of other animal species.     

Allometric scaling of resource acquisition by ruminants in dynamic and heterogeneous environments

We present a mechanistic formulation of the intake response of ruminants to vegetation biomass based solely on physiological and morphological parameters that scale allometrically with the animal's body mass. The model is applied to describe herbivore-vegetation interactions in dynamic and heterogeneous landscapes with low quality but abundant “tall grass” and high quality but sparsely available “short grass”, under two conditions: “uncoupled” (such that the effect of food intake on vegetation biomass can be neglected), or “coupled” (such that the vegetation biomass is determined by herbivore feeding). The results show that under uncoupled conditions, the minimum acceptance (proportion of vegetation consumed by the herbivore) at which the herbivore can leave its current patch without reducing its intake rate is when it has depleted the current patch by the energetic cost required to travel to another patch. The maximum acceptance at which the herbivore should leave its patch is when it has depleted the current patch by the cumulative energetic cost of traveling, handling, cropping, and digesting. Under coupled conditions, the optimal acceptance equals half the relative growth rate of the vegetation. Analytical solutions are obtained for equilibrium values for utilization of the vegetation, and for the densities of vegetation and ruminants, expressed in physiological and morphological herbivore parameters.     

Models of withdrawing renewable and non-renewable resources based on Odum's energy systems theory and Daly's quasi-sustainability principle

This paper presents a theoretical model of withdrawing resources based on Odum's energy systems diagrams. According to the theory of a general pulsing principle, withdrawing resources changes in time shifting from the initial phases of growth and maturity to the phases of descent and low energy restoration. A simulation was performed in order to hypothesize potential future trends of withdrawing renewable and non-renewable resources and to show some aspects of their sustainability–unsustainability, respectively. According to Odum's theory, after the rapid growth of the last century, our civilization is living in a climax transition phase and it is now approaching a descent phase. A “way down” will be necessary due to the exhaustion of non-renewable and to the limited use of renewable resources. An integrated “renew–non-renew” model was developed by Odum to show how a “business as usual” trend will bring us to a drastic transition to a world that uses scarce renewable resources. Nevertheless, a different choice is possible, based on Daly's concept of quasi-sustainability that can inspire a new model. The latter argued that the exploitation of a non-renewable resource must be paired with a compensating investment in a renewable substitute. Our model shows that we can use non-renewable resources better to considerably improve our capacity of capturing renewable resources in the future. We present this as a necessary condition to address a sustainable environmental policy.     

Projecting landscape changes in southern Chile: Simulation of human and natural processes driving land transformation

We describe a simulation model representing the most important human and natural factors driving land use and cover changes (LUCC) in southern Chile. We evaluate the model by examining its ability to simulate LUCC observed over the past three decades, conduct a sensitivity analysis of simulated trends to changes in important model parameters, and use the model to project likely landscape transformations over the next decade under “as usual,” “pessimistic,” and four “optimistic” scenarios. The model consists of five submodels representing LUCC on two distinct soil formations (volcanic ash and gleysols) and four major land use categories: native forest, agricultural land, shrubland, and urban land. Land use and cover sub-categories include old growth forests, secondary forests, and low and flooded shrubland. The model simulated well general historic trends in forest cover, agricultural land, shrubland, and urban land: from a forest-dominated landscape in 1976 to a landscape dominated by shrubland and agricultural land by 2007. Forest loss, forest degradation by logging and clearing for agriculture were the most important direct drivers of LUCC: forest logging and clearing were most important from 1976 to 1985, whereas after 1985 logging for firewood, driven by population growth, was most important. Sensitivity analysis indicated that model projections of general trends in the main land use and cover categories were not overly sensitive to changes in important model parameters, although further study is necessary to improve our estimates of the proportion of pasture requirements supplied by clearing low shrubland. Projections of LUCC suggested that a reduced amount of secondary forest would be left by 2017 if no actions are taken to reduce forest loss (“as usual”). Increasing population (“pessimistic scenario”) resulted in similar trajectories than those predicted by the as usual scenario, whereas reducing logging for firewood and increasing forest recruitment from shrubland could reduce loss of native forest by nearly one-third (“optimistic scenarios”). Surprisingly, shrubland exhibited the most complex and influential dynamics in all scenarios, being the immediate outcome of forest loss and the main long-term source of land for agriculture, urban expansion, and forest recovery. Few studies in Chile, or elsewhere, have considered the importance of this intermediate successional stage. Of the scenarios simulated, financial incentives targeted toward channeling shrubland into regenerated forest seemed most promising, although obstacles to such a management strategy exist.     

Weather,salience of climate change and congressional voting

Climate change is a complex long-run phenomenon. The speed and severity with which it is occurring is difficult to observe, complicating the formation of beliefs for individuals. We use Google search intensity data as a proxy for the salience of climate change and examine how search patterns vary with unusual local weather. We find that searches for “climate change” and “global warming” increase with extreme temperatures and unusual lack of snow. Furthermore, we demonstrate that effects of abnormal weather extend beyond search behavior to observable action on environmental issues. We examine the voting records of members of the U.S. Congress from 2004 to 2011 and find that members are more likely to take a pro-environment stance on votes when their home state experiences unusual weather.     

Ecosystem services as a counterpart of emergy flows to ecosystems

A generic input-state-output scheme has been used to represent ecosystem dynamics. Systemic approaches to ecosystems use functions that are based either on inputs, state or outputs of the system. Some examples of approaches that use a combination of functions have been recently proposed. For example the use of eco-exergy to emergy flow can be seen as a mixed input-state approach; more recently, to connect the state to the output of the ecosystem, the relation of eco-exergy and ecosystems services has been proposed. This paper studies the link between the useful output of an ecosystems and its input through the relation between ecosystem services and emergy flow, in a kind of grey/black box scheme (i.e., without considering the state and the structure of the ecosystem). No direct connection between the two concepts can be determined, but identifying and quantifying the emergy flows feeding an ecosystem and the services to humans coming from them facilitate the sustainable conservation of Nature and its functions. Furthermore, this input-output relation can be established in general by calculating the ratio of the value of the ecosystem services to the emergy flow that supports the system. In particular, the ratio of the world ecosystem services to the emergy flow supporting the entire biosphere has been calculated showing that, at least at the global level, Nature is more efficacious in producing “money” (in form of ecosystem services) than economic systems (e.g., national economies and their GDP).     

Implications of network particle tracking (NPT) for ecological model interpretation

Network particle tracking (NPT), building on the foundation of network environ analysis (NEA), is a new development in the definition of coherence relations within and between connected systems. This paper evaluates three ecosystem models in a comparison of throughflow- and storage-based NEA and NPT. Compartments in models with high indirect effects and Finn cycling showed low correlation of NEA storage and throughflow with particle repeat visits and numbers of particles in compartments at steady state. Conversely, the correlation between NEA and NPT results was high with two models having lower indirect effects and Finn cycling. Analysis of ecological orientors associated with NEA showed NPT to fully support conventional NEA results when the common conditions of donor control and steady state are satisfied. Particle trajectories are recorded in the new concept of a particle “passport”. Ability to track and record particle in-system histories enables views of multiple scales and opens the possibility of making pathway-dependent modeling decisions. NPT may also enable modeling of time, allowing integration of Newtonian, organismal and stochastic modeling perspectives in a single comprehensive analysis.     

Modeling a wetland system: The case of Keoladeo National Park (KNP), India

A model for the wetland part of KNP is presented and analyzed. Two-dimensional parameter scans suggest that this minimal model possesses dynamical complexities. Per capita availability of water to “bad” biomass (W₁) is one of the most vital parameters. One can ensure good health of the park by restricting the par capita availability of water to low values. Getting the “bad” biomass removed by granting permits to villagers should go hand in hand with water management and conservation activities. The model presented in this paper may be helpful in designing the timing and nature of human interventions in the form of implementation of well worked out policies in future.     

Effects of worker genotypic diversity on honey bee colony development and behavior (Apis mellifera L.)

There have been numerous reports of genetic influences on division of labor in honey bee colonies, but the effects of worker genotypic diversity on colony behavior are unclear. We analyzed the effects of worker genotypic diversity on the phenotypes of honey bee colonies during a critical phase of colony development, the nest initiation phase. Five groups of colonies were studied (n = 5–11 per group); four groups had relatively low genotypic diversity compared to the fifth group. Colonies were derived from queens that were instrumentally inseminated with the semen of four different drones according to one of the following mating schemes: group A, 4 A-source drones; group B, 4 B-source drones; group C, 4 C-source drones; group D, 4 D-source drones; and group E, 1 drone of each of the A-D drone sources. There were significant differences between colonies in groups A-D for 8 out of 19 colony traits. Because the queens in all of these colonies were super sisters, the observed differences between groups were primarily a consequence of differences in worker genotypes. There were very few differences (2 out of 19 traits) between colonies with high worker genotypic diversity (group E) and those with low diversity (groups A-D combined). This is because colonies with greater diversity tended to have phenotypes that were average relative to colonies with low genotypic diversity. We hypothesize that the averaging effect of genotypic variability on colony phenotypes may have selective advantages, making colonies less likely to fail because of inappropriate colony responses to changing environmental conditions.     

What does ecological modelling model? A proposed classification of ecological niche models based on their underlying methods

Species distribution model is the term most frequently used in ecological modelling, but other authors used instead predictive habitat distribution model or species-habitat models. A consensual ecological modelling terminology that avoids misunderstandings and takes into account the ecological niche theory does not exist at present. Moreover, different studies differ in the type of niche that is represented by similar distribution models. I propose to use as standard ecological modelling terminology the terms “ecological niche”, “potential niche”, “realized niche” models (for modelling their respective niches), and “habitat suitability map” (for the output of the niche models). Therefore, the user can understand more easily that models always forecast species’ niche and relate more closely the different types of niche models.     

A revised calculation of the econometric factors α- and β for the Extended Exergy Accounting method

Extended Exergy Accounting (“EEA”) is a method to compute the space- and time integral of the primary exergy required to produce a good or a service: the extended exergy of a commodity measures its “embodied exergy”, including externalities (Labour, Capital and Environmental Costa). A crucial point of the method is the calculation of two econometric coefficients, commonly referred to as “α” and “β”,used to calculate the extended exergy equivalents of Labour and Capital respectively. In previous applications of the EEA method, these coefficients have been assigned approximate values estimated on the basis of global system considerations. In this paper, a novel procedure is described that leads to the calculation of “exact” values of both econometric coefficients, based on detailed exergy- and monetary balances of the Society to which the EEA is applied. It is shown that both α and β depend in a non-trivial way from the consumption patterns, the technological level and the life- and socio-economic standards of each Country. It is also shown that the values are substantially different for developed (OECD) and underdeveloped Countries, and representative samples of values are calculated and critically analysed. On the basis of these new model coefficients, the specific exergy equivalents of Labour (ee_L) and of Capital (ee_K) are calculated, and shown to differ from the values used in previous EEA calculations.     

Establishment patterns in a secondary tree line ecotone

On semi-open pre-alpine fen pastures Alder encroachment creates a dynamic mosaic of grassland and woodland, which is rich in ecotones from fen to Carr. The structural diversity in colonisation patterns of Alder on fens suggests a dependency on multiple environmental drivers. Unidirectional progressive ecotone development provides an opportunity to address a current deficit in understanding successional patterns, i.e. process-pattern relationships in a multiple factor regime.We developed an individual-based model of Alder establishment on fen grassland to investigate the dependency of encroachment patterns upon seed production, dispersal distances and safe site availability. The purpose of the model is to provide a causal understanding of establishment patterns of Alder. In the model, all life processes of Alder individuals were parameterised with field data. This allowed us to strictly perform bottom-up simulations and successfully check plausibility by comparing simulated establishment patterns of cohorts with observed ecotone structures.Simulation results show that establishment patterns strongly depend on environmental drivers. Spatial progression of Alder encroachment and width of ecotones, respectively, mainly depend on wind speed during seed dispersal. Dense establishment of Alder leading to community change from fen grassland to Carr, requires windows of opportunity, which are defined by the rare coincidence of widespread dispersal, high seed production and favorable establishment conditions. Life-history traits of Alder (mast year cycle, high seed weight, weak establishment in fen) spatially and temporarily constrain the encroachment process. The structural diversity of long-term encroachment patterns is explained by the event-driven character of encroachment.Modelling individual establishment pathways of seedlings starting from germination revealed an endogenous stochasticity in establishment patterns emerging from low seed densities in the tail of the dispersal function. We conclude an inherent stochastic structure of dispersal-limited tree line ecotones, which limits reconstruction of processes from patterns.In order to describe long-term successional patterns of Alder encroachment at landscape scale, we propose the combination of two concepts: deterministic “patch-movement” of Alder woodland driven by continuous ecotone migration together with rare and stochastic “infiltration” of single Alder trees into open fen grasslands. Conservation management can control predictable “patch-movement” by cutting off maturing saplings around existing Alder woods. But the preservation of the actual large proportion of open grassland in fen pastures from infiltrating Alder seedlings and from the subsequent shift of the pasture to a densely wooded state would require mowing additionally to extensive grazing.     

Climate treaties and approaching catastrophes

If the threshold that triggers climate catastrophe is known with certainty, and the benefits of avoiding catastrophe are high relative to the costs, treaties can easily coordinate countries' behavior so as to avoid the threshold. Where the net benefits of avoiding catastrophe are lower, treaties typically fail to help countries cooperate to avoid catastrophe, sustaining only modest cuts in emissions. These results are unaffected by uncertainty about the impact of catastrophe. By contrast, uncertainty about the catastrophic threshold normally causes coordination to collapse. Whether the probability density function has “thin” or “fat” tails makes little difference.     

The value of information for integrated assessment models of climate change

We estimate the value of information (VOI) for three key parameters of climate integrated assessment models (IAMs): marginal damages at low temperature anomalies, marginal damages at high temperature anomalies, and equilibrium climate sensitivity. Most empirical studies of climate damages have examined temperature anomalies up to 3 °C, while some recent theoretical studies emphasize the risks of “climate catastrophes,” which depend on climate sensitivity and on marginal damages at higher temperature anomalies. We use a new IAM to estimate the VOI for each parameter over a range of assumed levels of study precision based on prior probability distributions calibrated using results from previous studies. We measure the VOI as the maximum fixed fraction of consumption that a social planner would be willing to pay to conduct a new study before setting a carbon tax. Our central results suggest that the VOI is greatest for marginal damages at high temperature anomalies.     

Testing the impact of social forces on the evolution of Sahelian farming systems: A combined agent-based modeling and anthropological approach

This article presents the results of a methodology based on an extensive sociological fieldwork in three different sites settled along a gradient of aridity in Nigerien Sahel. This fieldwork led to build a set of rules for the behaviour of individuals in non-pastoralist villages. We implemented these rules into an agent-based model simulating three village archetypes. Each archetype includes biophysical, economical, social agricultural and livestock modules. Results from simulations with no social transition processes show that villages specialize themselves into different economic activities according to natural resource specificities: A decreasing intensification gradient is observed from the most favoured site, with more local productions and good ecological indicators, to the less-favoured site, with a growing proportion of the population wealth coming from migration remittances and “off-shore” livestock. Two family transition processes were implemented, following field observations and literature-based hypotheses: family organizations evolve between a patriarchal mode and a non-cooperative mode following tensions due to income redistribution. Family inheritance systems evolve from a “customary” one-heir mode to a “local Muslim” mode in which all males inherits land. This evolution depends on family tensions due to land availability. Once introducing these processes, the population of each site differentiates itself into specialized groups according to size, assets and social status. Meanwhile, the group proportions and specializations strongly vary according to the sites but they are all characterized by the emergence of individualistic family types and the increase of the village populations’ robustness.