To this end, researchers from INRA, CNRS, and CEA investigated the relationships between climate conditions and wheat crop yields over time in a large-scale study whose results shed light on the conditions leading to such exceptional decreases.
Unprecedented climate conditions linked to record drops in yield
Surprisingly warm temperatures at the end of the autumn (high temperatures near 11°C in December 2015); extremely elevated precipitation levels (4.4 mm per day in May 2016), abnormally low solar radiation and evapotranspiration levels in the spring: such was the exceptional climate situation in 2015-16. Detrimental to wheat growth but favorable to the growth of fungal diseases, these remarkable conditions, some of which had not been observed since 1958, coincided with an exceptional decrease in production.
By analyzing the impact of such climate extremes on wheat production between 1958 and 2016, the researchers demonstrated that the excess of spring precipitation was as harmful for crop yields as the abnormally high temperatures of the preceding fall. This means that if the number of autumn days with temperatures between 0°C and 10°C decreases by half (from 20 to 10, for example) followed by a spring with above-average precipitation, the probability of an extreme decrease in yield, i.e., over 10%, doubles, to reach 50%.
What 2016 suggests for the future
As part of climate projections, researchers anticipate an increase in fall temperatures by 2050. This evolution may mean that, in the future, the very mild temperatures of December 2015 might occur more often in France’s main wheat producing region. On the other hand, there are no clear trends in precipitation levels for spring, from April to July.
This research highlights the benefit of analyzing climate conditions together with agricultural production levels. This work emphasizes a new type of climate impact which, beyond opening new avenues for research, raises questions about the vulnerability of current and future production systems when confronted with climate extremes.
At the heart of the study
The scientists used agronomic and climate data from France's main wheat producing region, which includes 27 departments located in the following regions: Bourgogne-Franche-Comté, Centre-Val de Loire, Grand Est, Hauts-de-France, Île-de-France, Normandie, Nouvelle-Aquitaine and Pays de la Loire.
By cataloguing the climate conditions experienced in this regions between October 1958 and July 2016, the researchers considered a series of climate variables by month or by season: high and low temperatures, precipitation, solar radiation, potential evapotranspiration, and the number of days the high temperature exceeded 34°C or was between 0°C and 10°C (a period of cold required by the plant to transition from a vegetative to a productive state) and precipitation from October to July.
[1] The Agronomy unit (INRA/AgroParistech), Laboratory of Climate and Environmental Sciences (CNRS/CEA/UVSQ) and Laboratory for Climate, Environment, Coupling and Uncertainties (CNRS/Cerfacs) are working together on this project which is part of the Institute for Convergence (CLAND: https://cland.lsce.ipsl.fr/.