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Christian Mazza & Louis-Félix Bersier

First part (Christian Mazza)

Title: Structural instabilities of ecosystem dynamics


Abstract: We consider the stability and feasibility of the equilibria reached by mathematical models of ecosystem dynamics, by focusing on Lotka-Volterra web dynamics and McArthur consumer-resource models. We will first recall basic fundamental results like May stability condition for random Lotka-Volterra dynamics. We will then present recent results from the literature concerning structural instabilities of ecosystem dynamics. Even small structural changes in these models, like those that might occur due to climate change, will result in persistent abundance fluctuations that can be dramatic, and even drive species to extinction.

Second part (Louis-Félix Bersier) 

Title: Effect of temperature change on the functioning of natural communities


Abstract: Natural communities (e.g. plants in meadows) provide essential services, e.g., food production, carbon sequestration, climate regulation (see the recently launched international program on biodiversity and ecosystem services, It has been shown experimentally that more diverse communities perform better than depauperated ones, for example in term of biomass production. This is known as the BEF relationship (BEF: Biodiversity-Ecosystem Functioning).

In this presentation, we will first study a general model for the BEF relationship. Then, we will explore how increasing temperature affects this relationship. We will use here the Arrhenius equation that relate vital rates to temperature. Such models are essential to be able to predict the effect of temperature on biological phenomena. They are called Thermal Performance Curve (TPC) and we will discuss existing models.


Julia Steinberger

Title: Squaring the circle : measuring and modelling how to lower energy demand as part of climate mitigation

Acting on climate means changing how energy is produced and consumed. In this session, I will cover an understudied aspect of climate action: reducing energy demand. This requires understanding how different sectors use energy and for what purpose, as well as what types and quantities of energy services are necessary to realise decent living standards. What kinds of transformations are possible and necessary, and how can we quantitatively advance them?


Philippe Jacquod

Title: Electrification of the energy sector and its impact on power systems

The energy sector is responsible for almost three-quarter of global greenhouse gas emissions. Electrification of the energy sector, in parallel to the massive development of renewable sources of electric power has been suggested as the way to decarbonize it - but is this program at all
possible ? And if yes, what does it require in terms of new infrastructures ? In this talk, I will evaluate the impact that electrification is expected to have on electric power systems and address these questions from a swiss and European perspective with some focus on mathematical aspects of electric power grids.


Florence Hugard

Title: What is the role of finance in the transition?

Abstract: Finance is often pointed as one of the key tools to drive the transition to an economy that is resilient, inclusive and respecting planetary boundaries. But how can it be effective in fostering this necessary transition of the real economy? Investors and financiers can be active at three levels: they can wean firms off financial capital when they are not aligned with the goals of society, they can accompany firms on their journey towards sustainability and they can provide financing to projects positive in regards to the transition. These three types of interventions of the financial sector however have different levels of effectiveness and can present limitations.


Valérie Chavez

Title: Extreme value theory and climate extremes


Abstract: The past few decades have seen extreme climate events affecting all regions of the world with catastrophic impacts on human society. Quantifying the risk of such events is difficult but necessary. In this context methodologies based on extreme value theory play an important role. Extreme value theory is the field of statistics dedicated to the study of events with low occurrence frequencies and large amplitudes.  Such events are necessarily rare in relation to the bulk of a population, which makes them hard to model and difficult to predict. 


Martine Rebetez

Title: Decades of disinformation about climate change

Abstract: Climate change has been and is still subject to important disinformation campaigns financed by fossil energy companies. These campaigns include the use of fake data series but more often of inappropriate data or inappropriate contexts. They also include well-chosen or unfortunate scientific vocabulary, subject to misunderstandings by lay people.

Communicating about climate change and more generally about scientific results, we have to be aware of such potential misunderstandings and misuses by private interests.

This presentation will show examples of deliberate or unfortunate misuses of scientific results, data and vocabulary.


Quentin Gallea

Title: Greening the energy production: from potential to implementation 

Abstract: With the current energy and climate crisis, the call to increase renewable energy production is more pressing than ever. Despite the technological innovations in renewable energy making-it more accessible, the pace to adopt those technologies remains often slow. In the present paper, we explore how countries react to technological innovation in renewable energy and what increase their investments in renewable energy production. In particular, we show that technological improvement increases the production capacity on average and countries with higher potential (e.g. more wind) reacts more. Additionally, we find that a necessary condition is to have access to engineers and scientists in the country in order to actively react to investments incentive (e.g. better technology). A key element of the paper is that we address endogeneity issues by exploiting time invariant geographical factors as well as global technological shocks. 

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