### Chair: Sacha Epskamp

 246 Coupled societies are more robust against collapse: A hypothetical look at Easter Island [abstract]Abstract: Inspired by challenges of environmental change and resource limitations experienced by modern society, recent decades have seen an increased interest in understanding and modelling the long-term development of past societies. A particular focus in this analysis has been on mechanisms that can cause collapse or enable the long term sustainability of a society. A widespread framework to model societal evolution has been dynamical systems theory, which can naturally capture the interaction of multiple sub-systems. Modelling efforts so far have focussed on single, isolated societies, while interactions, or networks of multiple coupled socio-environmental systems have not been considered. In this talk we propose a model of societal evolution that describes the dynamics of a population that harvests renewable resources and manufactures products that can be accumulated. Applying the model to Easter Island gives a good fit to the archaeological record. Collapse is driven by a bifurcation that occurs when the rate of extraction of natural resources is increased beyond a critical point. We present numerical and analytical analysis of the bifurcation diagram. In the second part of the talk we analyse the diffusion and targeted movement of wealth, people, and resources between two societies. Specifically, we investigate how a diffusive coupling and a wealth-driven coupling change the population levels and their distribution across the two societies compared to uncoupled, independent societies. We find that the region of parameter space in which societies can stably survive in the long term is significantly enlarged when coupling occurs in both social and environmental variables. The objective of the talk is to show how the phenomenon of societal collapse can be quantified and how the interaction of multiple coupled socio-environmental systems can be modelled. Attendees will gain insights into novel applications of dynamical system theory and network science. Sabin Roman, Seth Bullock and Markus Brede 512 Patterns of Human Synchronization [abstract]Abstract: Social media are transforming global communication and coordination and provide unprecedented opportunities for studying socio-technical domains. Here we study global dynamical patterns of communication on Twitter across multiple scales. In particular, we study collective activities across geographical scales, from areas smaller than one square kilometer up to the global scale. Underlying the observed patterns is both the diurnal rotation of the earth, day and night, and the synchrony required for contingency of actions between individuals. We find that urban areas show a cyclic contraction and expansion that resembles heartbeats linked to social rather than natural cycles, mainly determined by daily routines of work, rest and recreation. Different urban areas have characteristic signatures of daily collective activities, varying the shape and location of peaks and valleys of activity. We show that the differences detected are consistent with a new emergent global synchrony that couples behavior in distant regions across the world, in part due to the communication power provided by social media. Although local synchrony is the major force that shapes the collective behavior in cities, a larger-scale synchronization is beginning to occur. Alfredo J. Morales, Vaibhav Vavilala, Rosa M. Benito and Yaneer Bar-Yam Global Patterns of Human Synchronization, arXiv:1602.06219, 2016 Alfredo Morales, Vaibhav Vavilala, Rosa M. Benito and Yaneer Bar-Yam 245 Rabies virus persistence in dog population in Central African Republic [abstract]Abstract: Rabies is a fatal zoonosis caused by the RABV virus and characterized by a complex epidemiological situation that remains a serious public health problem in developing countries. Rabies incidence is largely attributed to the growth of domestic dog population considered as the most important vector for human exposure. Phylogenetic and virological analysis of isolates collected in Bangui, the capital city of the Central African Republic, indicate the presence of sequentially circulating subtypes and a reproductive number close to one. None of these subtypes seem to persist in the sole population of Bangui and mechanisms underlying virus persistence remain unknown. Two main factors may be at play: the spatial fragmentation of the host population, favoring the importation of isolates from outside the city, and the heterogeneous incubation period. To study the role and interplay of these different layers of complexity on the RABV epidemiology, we built a spatially explicit stochastic metapopulation epidemic model, inferring dog settlements from human demographic data and considering realistic long-tail distributions for incubation and infectious periods. By exploring different epidemic scenarios, we found that the virus can persist even for very low transmissibilities maintaining a stable dog population, and producing invasion cycles in agreement with empirical observations. Interestingly, no persistence would be observed for the same parameters once an exponentially distributed incubation periods is considered. Our findings illustrate how multiple layers of complexity (both ecological and epidemiological) are needed to sustain virus persistence and identify the factors to target for epidemic control. Vittoria Colizza, Davide Colombi, Chiara Poletto, Emmanuel Nakoune and Herve Bourhy 224 Stability and feasibility of large ecosystems: from structure to function [abstract]Abstract: The coexistence of species in large ecosystems has been a longstanding problem in ecology. Since the seminal work by May, we have tools and methods to study local asymptotic stability in terms of random matrices. This results can be generalized to include the effect of empirical network structures. Stability is not the whole part of the issue. It is related to perturbation of population abundances, while feasibility (or structural stability) is related to perturbations of growth rates and to the volume of the domain of growth rates leading to positive population. Feasibility and stability, are different but not independent properties. In this talk, I will show how feasibility can be connected to different properties of interactions networks. [S. Allesina, J. Grilli, G. Barab\'as, S. Tang, J. Aljadeff and A. Maritan. Predicting the stability of large structured food webs. Nature Communications. 6:7842. 2015] [J. Grilli, M. Adorisio, S. Suweis, G. Barab\'as, J.R. Banavar, S. Allesina and A. Maritan. The geometry of coexistence in large ecosystems. arxiv 1507.05337] Jacopo Grilli 513 Emergent income inequalities in a social-ecological system [abstract]Abstract: We present an analysis of the economic dynamics in a floodplain fishery system, focused on the connection between fishery governance and economic inequality. The use of one individual fishing technique – fishing canals – has been growing exponentially in our study area. We observe that this expansion is associated with increasing inequality in fishing incomes, which is consistent with a lognormal distribution. Studying the current revenues of canals of different age, we show that the onset of this dynamics (intensified canal use, increasing inequality) occurred during a transition period in the 1970s. In the region of analysis, this decade was characterized by a combination of ecological stress (Sahelian drought and increasing population) and liberalization of the fishery through the breakdown of traditional oligarchic rule. We argue that, while this change in governance brought fairer opportunities to floodplain fishermen, its combination with ecological stress has led to an increase in economic inequality. Sarah Laborde, Riccardo Gallotti, Ian Hamilton, Aboukar Mahamat and Mark Moritz

### Chair: Saskia Werners

 404 Virus-like Dynamics for Modeling the Emergence of Defectors in the Spatial Public Goods Game [abstract]Abstract: In the last years, scientists coming from different communities investigated several socio-economic and biological phenomena under the lens of Evolutionary Game Theory (EGT). In general, studying the evolution of a population and identifying strategies that trigger cooperative behaviors constitute some of the major aims in this field. In particular, the emergence of cooperation becomes really interesting when agent interactions are based on games having a Nash equilibrium of defection, as in the Public Goods Game (PGG). The latter is analyzed by adding a viral spreading process based on the Susceptible-Infected-Susceptible (SIS) model. Notably, we consider a virus, with a spreading rate $\lambda$, whose effect is turning cooperators to defectors. In doing so, we can merge the two dynamics, i.e. the PGG and the epidemic spreading, in order to study the equilibria reached by the population. In particular, we analyze the relation between the spreading rate $\lambda$ (epidemic process) and the synergy factor (PGG). The proposed model aims to represent complex competitive processes, as the emergence of tumors. Notably, the latter, on a quality level, can be interpreted as the emergence of defection among the cells of an organism. Since some forms of tumors seem to be triggered by viruses, as the Papilloma Virus (PV), we deem that our investigations might shed some light on these complex phenomena, even if studied by a theoretical approach. Results of investigations can be of interest for those researchers interested in interdisciplinary applications of mathematical and physical models in biology, and for those interested in theoretical biology. To conclude, beyond to show results of our work we want to highlight the link between EGT and Biology. Marco Alberto Javarone and Nicoletta Schibeci Natoli Scialli 523 What is the role of human decisions in restoring a clear lake? – Analysing incremental complexity of agent-based models [abstract]Abstract: Human decisions affect and are affected by ecological systems in multiple ways. Natural resource modeling has commonly focused on decisions of resource users or strategic planners in one way. We argue that the dynamics of social-ecological systems (SES), however, emerge from multiple social-ecological interactions that are the result of decisions from different actors. We exemplify this with the case of lake restoration, i.e. the ecological regime shift from a turbid to a clear water state which is influenced by decisions from lake managers (governance) and individual households (beneficiaries + polluters). House owners can affect the nutrient inflow, the main driver for the lakes state, through their choices of sewage treatment. The management challenge, in this case, stems from the temporal and spatial decoupling between lake use activities by beneficiaries and the activities from distant actors eventually polluting the lake. Beneficiaries are those that enjoy ecosystem services such as drinking water, fish and recreation provided by the lake. We developed a coupled agent-based and system dynamics model to explore different pathways of managing the activities affecting the lake state back towards the clear state. Hereby, we discriminate between the timing of regulation measures (institutional level), pathways of rule enforcement (individual-institutional link), and the households initial attitude (individual level) in their effects on lake restoration time lags. By our incremental approach, we build a faceted understanding of how sensitive lake restoration is on the macro level to individual actor traits in the human-decision model on the micro level. Concluding, we reflect on the importance of the empirical as well as theoretical basis for human-decision modeling to increase its relevance for model-based learning. Romina Martin and Maja Schlüter 200 Reinforcement Learning in Social-Ecological System Models [abstract]Abstract: Recognizing the Earth System as a coupled complex social-ecological co-evolutionary system is important to enrich the discourse on global sustainability. However, it is an open question how to meaningfully formalize social dynamics in the context of mathematical social-ecological systems modeling. Existing models of social-ecological interactions often use a system dynamics approach of aggregated quantities, thereby not being able to account for complex social network effects, social stratification and inequalities - all presumably central issues for global sustainability; other types of models incorporate these ideas, but put their focus rather on regional, case specific social-ecological systems and tend not to use a "first-principle" approach. In this work we combine the concept of reinforcement learning (RL) with a co-evolutionary social-ecological systems perspective by providing the social agents with RL decision methods, making them capable of dealing with complex environments. Analytical calculations and computer simulations were performed to explore this scheme. It offers a promising view on a "first principle" method on agent behavior capable of dealing with unknown, possibly nonlinear environments to reveal potential counter intuitive traps and boundaries hindering social and ecological sustainability. Wolfram Barfuss, Jonathan F. Donges and Jürgen Kurths 165 Concepts behind the climate strategies. How C40 and its members define adaptation and mitigation? [abstract]Abstract: Networks within cities have become a feature in environmental governance, in particular in relation to dealing with climate change. Previous research has shown that the initiatives, such as C40, have created learning opportunities globally. Quantitative analyses have shown that connections have been formed and cities are learning from each other. However, less is known about what kinds of information is being shared through these networks. The concepts of adaptation and mitigation fundamentally advocate change. How they are conceptualised affects the way the climate change is addressed in practice. Previous research has shown that adaptation can be conceptualised as adjusting to the changing climate conditions (adjustment-based adaptation), as transforming the structures of society causing vulnerability (transformational adaptation), or as a combination of the two (reformist adaptation), and a similar classification of degree of change can also be found for mitigation. In this paper, our aim is to find out the degree of change as stated in the adaptation and mitigation strategies the C40 network and its members advocate. We approach the governance of urban adaptation as a complex system and ask how these concepts are defined in the documents produced by the C40 network and in the strategies of its member cities. We conduct an analysis of documents produced by C40 network and its member cities’ climate strategies with a computer assisted method to get the general overview of how far the documents support change. The result is controlled and deepened by close-reading of a representative sample of documents. Our findings reveal the concepts behind the climate strategies of C40 and its member cities that search to be the world leaders in addressing climate change. This gives context to the best practices promoted by the C40 network and its member cities and makes it possible to analyse them more profoundly. Milja Heikkinen and Sirkku Juhola 71 Opinion dynamics under out-group discrimination [abstract]Abstract: On many economic, political, social, and religious agendas, disagreement among individuals is pervasive. For example, the following are or have been highly debated: whether abortion, gay marriage, or death penalty should be legalized or not; the scientic standing of evolution; whether taxes/social subsidies/unemployment benefits/(lower bounds on) wages should be increased or decreased; the effectiveness of alternative (or standard') medicine such as homeopathy. In the field of so-called "opinion dynamics", long-run disagreement among individuals is sometimes considered a challenge, since a large class of models such as the famous model of DeGroot learning (DeGroot, 1974; Golub and Jackson, 2010) predict long-run opinion consensus as long as individuals form a connected group. However, there have recently been several models suggested which include a mode of anti-conformity' or `opposition' that predict disagreement even among connected interacting agents. Here, we present another such model of negative relationships among interacting agents, which extends the classical model of DeGroot for opinion dynamics. Our contributions are that we provide precise game-theoretic motivations of individuals' behavior as well as mathematically rigorous results on long-run disagreement in connected societies. Our game-theoretic motivation is that agents wish to coordinate with their friends (their 'in-group') and anti-coordinate with their enemies (their 'out-group'). Such behavior is well-documented in social psychology, both within the laboratory (see, e.g., Taifel 1978; Fehrler and Kosfeld, 2013) and outside. Our mathematical results include very general conditions for persistent disagreement among connected agents as well as an exhaustive graph-theoretical classification of long-run opinions in certain special cases. We find that persistent disagreement 'easily' obtains under the presence of negative relationships. As a consequence, crowd wisdom, the condition when all individuals learn the true state of nature or come close to it, is likely to fail. Steffen Eger

### Chair: Vincent Traag

 332 Behavioural Economics in Social-Ecological Systems with Thresholds [abstract]Abstract: How does people behave when dealing with situations pervaded by thresholds? Imagine you’re a fisherman whose livelihoods depend on a resource on the brink to collapse, what would you do? and what do you think others will do? Here we report results form a field experiment with fishermen from four coastal communities in the Colombian Caribbean. A dynamic game with 256 fishermen helped us investigate behavioural responses to the existence of thresholds (probability =1 ), risk (threshold with a climate event with known probability of 0.5) and uncertainty (threshold with an unknown probability climate event). Communication was allowed during the game and the social dilemma was confronted in groups of 4 fishermen. We found that fishermen facing thresholds presented a more conservative behaviour on the exploration of the parameter space of resource exploitation. Some groups that crossed the threshold managed to recover to a regime of high fish reproduction rate. However, complementary survey data reveals that groups that collapsed the resource in the game come often from communities with high livelihood diversification, lower resource dependence and strongly exposed to infrastructure development. We speculate that the later translates on higher noise levels on resource dynamics which decouples or mask the relationship between fishing efforts and stock size encouraging a more explorative behaviour of fishing effort in real life. This context is brought to our artificial game and leaves statistical signatures on resource exploitation patterns. In general, people adopt a precautionary behaviour when dealing with common pool resource dilemmas with thresholds. However, stochasticity can trigger the opposite behaviour. Juan Carlos Rocha Gordo, Caroline Schill, Therese Lindahl and Anne Sophie Crépin 87 Self-Organization of Power-Law Vegetation Niches in Agriculture with Ecological Optimum [abstract]Abstract: Sustainable farming based on the self-organization of ecosystem is an important alternative for smallholders. In contrast to conventional monoculture system based on a strong control and load to environment, complex systems perspective can provide biodiversity-based polyculture, in which various emergent ecosystem functions serve as a principal source of productivity and resilience. This article investigates the statistics of vegetation cover in ecological optimum with a simple model of niche differentiation, and discuss the origin of power law observed in field data. We also focus on farming application and analyze the yield in response to crop diversity. Power-law distribution of crops diverges the mean yield of single crop into large fluctuation, therefore it requires alternative conception of yield at plant community level. With the use of information entropy as management cost and basic conception of measure integration of niche distribution, basic strategy of adaptive diversification of vegetation portfolio is proposed, in order to assure minimum harvest for food security in changing environment. Statistics of natural vegetation and mixed polyculture of crops are demonstrated for the proof of concept. Masatoshi Funabashi 60 On the emergence of cooperation under vigilance: a multiplex network approach [abstract]Abstract: Understanding the evolution of cooperation is one of the most fascinating challenges in many disciplines. There is a large amount of literature analysing the mechanisms for cooperation to emerge and to be sustained, both from theoretical and experimental studies. Another way to understand the evolution of cooperation in human societies consist in deciphering the cooperative behaviour in ancient communities from historical records. In a previous work we studied cooperation in the Yamana society that inhabited Argentina and observed that the emergence of an informal network of vigilance promoted cooperation. Several field studies have found evidence of humans exposing a pro-social behaviour when being observed by others and also under the presence of subtle cues of being watched. The observability effect (the increase of cooperation under vigilance) seems to be driven by our reputational concerns, bringing the indirect reciprocity mechanism into play. This work explores the effect of vigilance on cooperation in networked systems, in the framework of the Prisoners’ Dilemma game. We study the bidirectionally-coupled vigilance and game dynamics. We quantify the impact of the topological structure of the network, and the interplay between vigilance and behaviour, on the outcome of cooperation. Moreover, we study the impact of vigilance on cooperation when the individuals have to afford a cost to become vigilant actors. We also analyse the influence of network multiplexity, i.e. the interconnection of different topological structures for the vigilance and the game networks, and the impact of correlated multiplexity, i.e. when node degrees of the multiplex layers are not randomly distributed but correlated. Our results show that vigilant actors can significantly affect the levels of cooperation, not only by enhancing cooperation in regions of the phase diagram where cooperation is expected to hold, but also by altering the critical point for the emergence of cooperation. María Pereda 244 Cascading effects of critical transitions in social-ecological systems [abstract]Abstract: Critical transitions in nature and society are likely to occur more often and severe as humans increase they pressure on the world ecosystems. Yet it is largely unknown how these transitions will interact, whether the occurrence of one will increase the likelihood of another, and whether these potential teleconnections (social and ecological) correlate critical transition in distant places. Here we present a framework for exploring three types of potential cascading effects of critical transitions: forks, domino effects and inconvenient feedbacks. Drivers and feedback mechanisms are reduced to a network form that allow us to explore drivers co-occurrence (forks). Sharing drivers is likely to increase correlation in time or space among critical transitions but not necessarily interdependence. Random walks on causal networks allow us to detect and compare communities of common drivers and feedback mechanisms across different critical transitions. Domino effects and inconvenient feedbacks were identified by mapping new circular pathways on coupled networks that have not been previously reported. The method serves as a platform for hypothesis exploration of plausible new feedbacks between critical transitions in social-ecological systems; it helps to scope structural interdependence and hence an avenue for future modelling and empirical testing of regime shifts coupling. Juan Carlos Rocha Gordo