Vítor V. Vasconcelos

Climate policies under wealth inequality

Significance One of the greatest challenges in addressing global environmental problems such as climate change, which involves public goods and common-pool resources, is achieving cooperation among peoples. There are great disparities in wealth among nations, and this heterogeneity can make agreements much more difficult to achieve (e.g., regarding implementation of climate change mitigation). This paper incorporates wealth inequality into a public goods dilemma, including an asymmetric distribution of wealth representative of existing inequalities among nations. Without homophily (imitation of like agents), inequality actually makes cooperation easier to achieve; homophily, however, can undercut this, leading to collapse because poor agents may contribute less. Understanding such effects may enhance the ability to achieve agreements on climate change and other issues. Taming the planet’s climate requires cooperation. Previous failures to reach consensus in climate summits have been attributed, among other factors, to conflicting policies between rich and poor countries, which disagree on the implementation of mitigation measures. Here we implement wealth inequality in a threshold public goods dilemma of cooperation in which players also face the risk of potential future losses. We consider a population exhibiting an asymmetric distribution of rich and poor players that reflects the present-day status of nations and study the behavioral interplay between rich and poor in time, regarding their willingness to cooperate. Individuals are also allowed to exhibit a variable degree of homophily, which acts to limit those that constitute one’s sphere of influence. Under the premises of our model, and in the absence of homophily, comparison between scenarios with wealth inequality and without wealth inequality shows that the former leads to more global cooperation than the latter. Furthermore, we find that the rich generally contribute more than the poor and will often compensate for the lower contribution of the latter. Contributions from the poor, which are crucial to overcome the climate change dilemma, are shown to be very sensitive to homophily, which, if prevalent, can lead to a collapse of their overall contribution. In such cases, however, we also find that obstinate cooperative behavior by a few poor may largely compensate for homophilic behavior.

EVOLUTIONARY DYNAMICS OF CLIMATE CHANGE UNDER COLLECTIVE-RISK DILEMMAS

Preventing global warming requires overall cooperation. Contributions will depend on the risk of future losses, which plays a key role in decision-making. Here, we discuss an evolutionary game theoretical model in which decisions within small groups under high risk and stringent requirements toward success significantly raise the chances of coordinating to save the planets climate, thus escaping the tragedy of the commons. We discuss both deterministic dynamics in infinite populations, and stochastic dynamics in finite populations.

Climate change governance, cooperation and self-organization

When attempting to avoid global warming, individuals often face a social dilemma in which, besides securing future benefits, it is also necessary to reduce the chances of future losses. In this manuscript, we introduce a simple approach to address this type of dilemmas, in which the risk of failure plays a central role in individual decisions. This model can be shown to capture some of the essential features discovered in recent key experiments, while allowing one to extend in non-trivial ways the experimental conditions to regions of more practical interest. Our results suggest that global coordination for a common good should be attempted by segmenting tasks in many small to medium sized groups, in which perception of risk is high and uncertainty in collective goals is minimized. Moreover, our results support the conclusion that sanctioning institutions may further enhance the chances of coordinating to tame the planets climate, as long as they are implemented in a decentralized and polycentric manner.

Evolution of all-or-none strategies in repeated public goods dilemmas.

Many problems of cooperation involve repeated interactions among the same groups of individuals. When collective action is at stake, groups often engage in Public Goods Games (PGG), where individuals contribute (or not) to a common pool, subsequently sharing the resources. Such scenarios of repeated group interactions materialize situations in which direct reciprocation to groups may be at work. Here we study direct group reciprocity considering the complete set of reactive strategies, where individuals behave conditionally on what they observed in the previous round. We study both analytically and by computer simulations the evolutionary dynamics encompassing this extensive strategy space, witnessing the emergence of a surprisingly simple strategy that we call All-Or-None (AoN). AoN consists in cooperating only after a round of unanimous group behavior (cooperation or defection), and proves robust in the presence of errors, thus fostering cooperation in a wide range of group sizes. The principles encapsulated in this strategy share a level of complexity reminiscent of that found already in 2-person games under direct and indirect reciprocity, reducing, in fact, to the well-known Win-Stay-Lose-Shift strategy in the limit of the repeated 2-person Prisoners Dilemma.

Principal axes for stochastic dynamics

We introduce a general procedure for directly ascertaining how many independent stochastic sources exist in a complex system modeled through a set of coupled Langevin equations of arbitrary dimension. The procedure is based on the computation of the eigenvalues and the corresponding eigenvectors of local diffusion matrices. We demonstrate our algorithm by applying it to two examples of systems showing Hopf bifurcation. We argue that computing the eigenvectors associated to the eigenvalues of the diffusion matrix at local mesh points in the phase space enables one to define vector fields of stochastic eigendirections. In particular, the eigenvector associated to the lowest eigenvalue defines the path of minimum stochastic forcing in phase space, and a transform to a new coordinate system aligned with the eigenvectors can increase the predictability of the system.

Incomplete Cooperation and Co-Benefits: Deepening Climate Cooperation with a Proliferation of Small Agreements

Case study and model results lend some optimism for the potential of small coalitions with partially excludable public goods to substantially deepen international cooperation on energy and climate issues. Drawing motivation from other issue areas in international relations ranging from nuclear non-proliferation, transboundary air pollution and liberalized trade, we use an evolutionary-game-theoretic model to analyze regimes that yield domestic incentives to contribute to public goods provision (co-benefits). Co-benefits may be limited, but can create a nucleus for formation of coalitions that grow while deepening provision of global public goods. The Climate and Clean Air Coalition (CCAC) is a prime example of an agreement that employs partially excludable club benefits to deepen cooperation on non-CO2 greenhouse gases. Our game-theoretic results support two important insights for the building blocks approach to addressing climate change: sustained cooperation in club agreements is possible even when public goods are not entirely excludable and some members of the population free-ride; and second, cooperation in small club configurations yields larger non-excludable public goods benefits than cooperation in more inclusive forums. This paper lends positive support that a proliferation of small agreements under a building blocks approach at the UNFCCC may be more effective (not just more likely) for deepening climate change cooperation than a fully inclusive approach.

Co-evolutionary Dynamics of Collective Action with Signaling for a Quorum

Collective signaling for a quorum is found in a wide range of organisms that face collective action problems whose successful solution requires the participation of some quorum of the individuals present. These range from humans, to social insects, to bacteria. The mechanisms involved, the quorum required, and the size of the group may vary. Here we address the general question of the evolution of collective signaling at a high level of abstraction. We investigate the evolutionary dynamics of a population engaging in a signaling N-person game theoretic model. Parameter settings allow for loners and cheaters, and for costly or costless signals. We find a rich dynamics, showing how natural selection, operating on a population of individuals endowed with the simplest strategies, is able to evolve a costly signaling system that allows individuals to respond appropriately to different states of Nature. Signaling robustly promotes cooperative collective action, in particular when coordinated action is most needed and difficult to achieve. Two different signaling systems may emerge depending on Nature’s most prevalent states.

Stochastic dynamics through hierarchically embedded markov chains

Studying dynamical phenomena in finite populations often involves Markov processes of significant mathematical and/or computational complexity, which rapidly becomes prohibitive with increasing population size or an increasing number of individual configuration states. Here, we develop a framework that allows us to define a hierarchy of approximations to the stationary distribution of general systems that can be described as discrete Markov processes with time invariant transition probabilities and (possibly) a large number of states. This results in an efficient method for studying social and biological communities in the presence of stochastic effects-such as mutations in evolutionary dynamics and a random exploration of choices in social systems-including situations where the dynamics encompasses the existence of stable polymorphic configurations, thus overcoming the limitations of existing methods. The present formalism is shown to be general in scope, widely applicable, and of relevance to a variety of interdisciplinary problems.

Cooperation dynamics of polycentric climate governance

Global coordination for the preservation of a common good, such as climate, is one of the most prominent challenges of modern societies. In this manuscript, we use the framework of evolutionary game theory to investigate whether a polycentric structure of multiple small-scale agreements provides a viable solution to solve global dilemmas as climate change governance. We review a stochastic model which incorporates a threshold game of collective action and the idea of risky goods, capturing essential features unveiled in recent experiments. We show how reducing uncertainty both in terms of the perception of disaster and in terms of goals induce a transition to cooperation. Taking into account wealth inequality, we explore the impact of the homophily, potentially present in the network of influence of the rich and the poor, in the different contributions of the players. Finally, we discuss the impact of polycentric sanctioning institutions, showing how such a scenario also proves to be more efficient than a single global institution.

Climate governance as a complex adaptive system: reply to comments on "climate change governance, cooperation and self-organization".

a Centro de Biologia Molecular e Ambiental, Universidade do Minho, 4710-057 Braga, Portugal b Departamento de Matematica e Aplicacoes, Universidade do Minho, 4710-057 Braga, Portugal c ATP-Group, CMAF, Instituto para a Investigacao Interdisciplinar, 1649-003 Lisboa, Portugal d INESC-ID and Instituto Superior Tecnico, Universidade de Lisboa, Taguspark, 2744-016 Porto Salvo, Portugal e Centro de Fisica da Universidade do Minho, 4710-057 Braga, Portugal