Socio-Ecology  (S) Session 1

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. Close

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 Close

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. Close

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] Close

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. Close