The evolving agro-climatic risks related to the changing climate variability (dry spells and water balance) in a warming context

Started in December 2020

Funding: CIFRE contract with avec Groupama Rhône-Alpes Auvergne

Supervisors: Albin Ullmann & Thierry Castel

Abstract

Climate change modifies climatic hazards and requires a reconsideration of agro-climatic risks. In France, since the 1960s, climate change has resulted in an abrupt rise in surface air temperature around 1987/1988. These rapid changes in climatic hazards are likely to modify agro-climatic risks and lead to historic crop losses. Understanding the regional effects of climate change on agro-climatic risks is therefore a major challenge for the agricultural sector. Drought is one of the agro-climatic risks that have a major impact on crop production and climatic crop insurance. This work, which results from a collaboration between an insurance company and a research laboratory, investigates how and to what extent changes in climatic hazards affect drought risk, and ultimately the performance of climatic crop insurance. Since wheat, maize and vineyards are the main crops in the company’s portfolio, agro-climatic risk modifications will be studied specifically for these crops of interest. The Safran-Isba-Modcou dataset, produced by Météo-France, allows to quantify structural changes in climatic hazard linked to water cycle on a regional scale over the period 1959-2021. Taking crop vulnerability into account by using a simplified water balance model provides an opportunity to assess changes in water constraint for each production basin of the crops of interest. The definition of a water stress threshold for the crops studied enables to develop a drought index. The statistical distributions of the latter are probabilized using a Tweedie model, resulting in a regionalized characterization of drought risk structural modifications after the rapid warming observed in France. After the rapid warming of 1987/1988, evaporative demand increases sharply, particularly in spring and summer. This leads to a progressive drying-up of soil water reservoirs, increasing water stress on vegetation cover. Taking into account the vulnerability of the crops of interest shows that for winter bread wheat, for example, the water balance changes consequently. Periods when the water stress threshold is exceeded are lengthened or intensified with warming, depending on the production basin considered. These trends can be explained by a sharp increase in evapotranspiration. At the end of the growing season, changes in dry spells also play a role. This affects the structure of the drought-related agro-climatic risk, translating into an increase in the intensity and/or the occurrence of drought episodes. These changes depend on the production basin studied, and are associated with an increase in extreme droughts. The changes in drought risk, resulting from the rapid evolution of climatic hazards, affect sensitive crop stages, and can lead to significant yield losses. The performance of climatic crop insurance is therefore closely linked to changes in this type of risk. Given certain conditions, the drought index developed in this work shows a good correlation with the loss ratio used by insurance companies. This opens up new avenues for studying the volatility of climatic crop insurance performance. However, we need to refine and consolidate these results, which do not show any convincing improvement for certain crops such as wheat. The projection of these drought indices could help insurers to develop and experiment territorialized prevention and adaptation strategies that are relevant to all stakeholders.

Keywords

climate hazards, agro-climatic risks, drought, agriculture, France, climate change

Thesis advisory panel

Freddy Vinet, université Paul Valéry, UMR GRED, Montpellier
Benjamin Sultan, UMR Espace-Dev, Institut de Recherche pour le Développement, Montpellier

jury

Marie Launay, INRAE Provence Alpes Côte d’Azur, unité AgroClim – reviewer
Gilles Drogue, UFR SHS, université de Lorraine, Metz – reviewer
Nathalie Colbach, UMR1347 Agroécologie, université de Bourgogne, INRAE, Dijon –  examiner
Jean-Michel Soubeyroux, direction de la climatologie et des services climatiques, Météo France – examiner
Claude Perrot, Groupama Rhône-Alpes Auvergne – invited
Benjamin Bois, Institut universitaire de la vigne et du vin, Dijon – invited
Albin Ullmann, université de Bourgogne – UMR 6282 Biogéosciences – supervisor
Thierry Castel, Institut Agro Dijon – UMR6282 Biogéosciences – cosupervisor

extrait:

lien_externe:

titre:

Évolution des risques agro-climatiques en lien avec les modifications de l'aléa climatique (longs épisodes secs et bilan hydrique) en contexte de réchauffement

date_de_debut_these:

décembre 2020

nom:

Laurent

date_de_debut_these_numerique:

202012

kc_data:

a:8:{i:0;s:0:"";s:4:"mode";s:0:"";s:3:"css";s:0:"";s:9:"max_width";s:0:"";s:7:"classes";s:0:"";s:9:"thumbnail";s:0:"";s:9:"collapsed";s:0:"";s:9:"optimized";s:0:"";}

kc_raw_content:

The evolving agro-climatic risks related to the changing climate variability (dry spells and water balance) in a warming context

Started in December 2020

Funding: CIFRE contract with avec Groupama Rhône-Alpes Auvergne

Supervisors: Albin Ullmann & Thierry Castel

 

Abstract

Climate change modifies climatic hazards and requires a reconsideration of agro-climatic risks. In France, since the 1960s, climate change has resulted in an abrupt rise in surface air temperature around 1987/1988. These rapid changes in climatic hazards are likely to modify agro-climatic risks and lead to historic crop losses. Understanding the regional effects of climate change on agro-climatic risks is therefore a major challenge for the agricultural sector. Drought is one of the agro-climatic risks that have a major impact on crop production and climatic crop insurance. This work, which results from a collaboration between an insurance company and a research laboratory, investigates how and to what extent changes in climatic hazards affect drought risk, and ultimately the performance of climatic crop insurance. Since wheat, maize and vineyards are the main crops in the company's portfolio, agro-climatic risk modifications will be studied specifically for these crops of interest. The Safran-Isba-Modcou dataset, produced by Météo-France, allows to quantify structural changes in climatic hazard linked to water cycle on a regional scale over the period 1959-2021. Taking crop vulnerability into account by using a simplified water balance model provides an opportunity to assess changes in water constraint for each production basin of the crops of interest. The definition of a water stress threshold for the crops studied enables to develop a drought index. The statistical distributions of the latter are probabilized using a Tweedie model, resulting in a regionalized characterization of drought risk structural modifications after the rapid warming observed in France. After the rapid warming of 1987/1988, evaporative demand increases sharply, particularly in spring and summer. This leads to a progressive drying-up of soil water reservoirs, increasing water stress on vegetation cover. Taking into account the vulnerability of the crops of interest shows that for winter bread wheat, for example, the water balance changes consequently. Periods when the water stress threshold is exceeded are lengthened or intensified with warming, depending on the production basin considered. These trends can be explained by a sharp increase in evapotranspiration. At the end of the growing season, changes in dry spells also play a role. This affects the structure of the drought-related agro-climatic risk, translating into an increase in the intensity and/or the occurrence of drought episodes. These changes depend on the production basin studied, and are associated with an increase in extreme droughts. The changes in drought risk, resulting from the rapid evolution of climatic hazards, affect sensitive crop stages, and can lead to significant yield losses. The performance of climatic crop insurance is therefore closely linked to changes in this type of risk. Given certain conditions, the drought index developed in this work shows a good correlation with the loss ratio used by insurance companies. This opens up new avenues for studying the volatility of climatic crop insurance performance. However, we need to refine and consolidate these results, which do not show any convincing improvement for certain crops such as wheat. The projection of these drought indices could help insurers to develop and experiment territorialized prevention and adaptation strategies that are relevant to all stakeholders.

 

Keywords

climate hazards, agro-climatic risks, drought, agriculture, France, climate change

 

Thesis advisory panel

Freddy Vinet, université Paul Valéry, UMR GRED, Montpellier
Benjamin Sultan, UMR Espace-Dev, Institut de Recherche pour le Développement, Montpellier

 

jury

Marie Launay, INRAE Provence Alpes Côte d'Azur, unité AgroClim - reviewer
Gilles Drogue, UFR SHS, université de Lorraine, Metz - reviewer
Nathalie Colbach, UMR1347 Agroécologie, université de Bourgogne, INRAE, Dijon -  examiner
Jean-Michel Soubeyroux, direction de la climatologie et des services climatiques, Météo France - examiner
Claude Perrot, Groupama Rhône-Alpes Auvergne - invited
Benjamin Bois, Institut universitaire de la vigne et du vin, Dijon - invited
Albin Ullmann, université de Bourgogne - UMR 6282 Biogéosciences - supervisor
Thierry Castel, Institut Agro Dijon - UMR6282 Biogéosciences - cosupervisor