VIRGO

Inter-annual rainfall variability may foster lake regime shifts: An example from Lake Bourget in France

Jean-Denis Mathias — Wed, 27 Mar 2019 17:39:13 +0000

The Intergovernmental Panel on Climate Change anticipates increasing extreme rain events in the 21st century, leading to more frequent floods and more phosphorus transported into lakes, enhancing the risk of their eutrophication. This paper reports research assessing this risk on Lake Bourget in France, by coupling a statistical estimation of annual phosphorus transportation from annual rainfall and a dynamical model estimating the evolution of the phosphorus concentration in the lake in the period 2000–2050 according to yearly phosphorus transportation. The study of the model on the past suggests that the relative drought of the 2000s has fostered the effect of management measures to reduce phosphorus loading, enabling compliance with the Organisation for Economic Co-operation and Development guidance target for 2020. Simulations on different scenarios for the future show that a 10% increase in the rainfall standard deviation nearly doubles the probability of eutrophication, from 2.40% to 4.26% between 2016 and 2050.

Antoine Brias, Jean-Denis Mathias, Guillaume Deffuant,Inter-annual rainfall variability may foster lake regime shifts: An example from Lake Bourget in France,Ecological Modelling, Volume 389,2018,Pages 11-18,

Knowledge infrastructure and safe operating spaces in socio-ecological systems

Jean-Denis Mathias — Wed, 27 Mar 2019 17:17:00 +0000

Maintaining safe operating spaces for exploited natural systems in the face of uncertainty is a key sustainability challenge. This challenge can be viewed as a problem in which human society must navigate in a limited space of acceptable futures in which humans enjoy sufficient well-being and avoid crossing planetary boundaries. A critical obstacle is the nature of society as a controller with endogenous dynamics affected by knowledge, values, and decision-making fallacies. We outline an approach for analyzing the role of knowledge infrastructure in maintaining safe operating spaces. Using a classic natural resource problem as an illustration, we find that a small safe operating space exists that is insensitive to the type of policy implementation, while in general, a larger safe operating space exists which is dependent on the implementation of the “right” policy. Our analysis suggests the importance of considering societal response dynamics to varying policy instruments in defining the shape of safe operating spaces.

John M. Anderies, Jean-Denis Mathias, and Marco A. Janssen. PNAS March 19, 2019 116 (12) 5277-5284

An energy-like indicator to assess opinion resilience

Jean-Denis Mathias — Fri, 24 Nov 2017 15:20:50 +0000

Using the bounded-confidence model, with fixed uncertainties and extremists, we investigate how resilient the moderate mean opinion of a population is to the arrival in it of a new group of agents, when the energy of the opinion of this group (extremeness $\times ">$ group size) is varied. We say moderate mean opinion is resilient when, even though it may become temporarily more extreme after the arrival of the new agents, it later recovers its moderate value. We show that such resilience is displayed up to a threshold value of the equivalent energy of the group. We also show that when the agent-based model spontaneously converges to a single extreme, then this energy threshold is nil.

Link: http://www.sciencedirect.com/science/article/pii/S0378437116310135

On our rapidly shrinking capacity to comply with the planetary boundaries on climate change.

Jean-Denis Mathias — Fri, 24 Nov 2017 15:19:27 +0000

The planetary boundary framework constitutes an opportunity for decision makers to define climate policy through the lens of adaptive governance. Here, we use the DICE model to analyze the set of adaptive climate policies that comply with the two planetary boundaries related to climate change: (1) staying below a CO₂ concentration of 550 ppm until 2100 and (2) returning to 350 ppm in 2100. Our results enable decision makers to assess the following milestones: (1) a minimum of 33% reduction of CO₂ emissions by 2055 in order to stay below 550 ppm by 2100 (this milestone goes up to 46% in the case of delayed policies); and (2) carbon neutrality and the effective implementation of innovative geoengineering technologies (10% negative emissions) before 2060 in order to return to 350 ppm in 2100, under the assumption of getting out of the baseline scenario without delay. Finally, we emphasize the need to use adaptive path-based approach instead of single point target for climate policy design.

Link: https://www.nature.com/articles/srep42061

Multi-level policies and adaptive social networks – a conceptual modeling study for maintaining a polycentric governance system

Jean-Denis Mathias — Fri, 24 Nov 2017 15:17:43 +0000

Information and collaboration patterns embedded in social networks play key roles in multilevel and polycentric modes of governance. However, modeling the dynamics of such social networks in multilevel settings has been seldom addressed in the literature. Here we use an adaptive social network model to elaborate the interplay between a central and a local government in order to maintain a polycentric governance. More specifically, our analysis explores in what ways specific policy choices made by a central agent affect the features of an emerging social network composed of local organizations and local users. Using two types of stylized policies, adaptive co-management and adaptive one-level management, we focus on the benefits of multi-level adaptive cooperation for network management. Our analysis uses viability theory to explore and to quantify the ability of these policies to achieve specific network properties. Viability theory gives the family of policies that enables maintaining the polycentric governance unlike optimal control that gives a unique blueprint. We found that the viability of the policies can change dramatically depending on the goals and features of the social network. For some social networks, we also found a very large difference between the viability of the adaptive one-level management and adaptive co-management policies. However, results also show that adaptive co-management doesn’t always provide benefits. Hence, we argue that applying viability theory to governance networks can help policy design by analyzing the trade-off between the costs of adaptive co-management and the benefits associated with its ability to maintain desirable social network properties in a polycentric governance framework.

Link: https://www.thecommonsjournal.org/articles/10.18352/ijc.695/