Changes in frequency of occurrence of dry/wet years and its implications on the Spanish agro-food system sustainability

Agrofood systems can be described with several interconnected compartments, namely cropland, grassland, livestock and people. For any attempt of optimising or improving the system it is essential to understand each one of them and how they are interrelated.

The analysis of these connections improves the general understanding of the full system, helping to identify potential hot spots of production and system leakages in pursuit of sustainability. It is also useful to measure the degree of external dependency or independency, and therefore contributing to assess potential hazards for food security. The GRAFS methodology (General Representation of Agro-food Systems) (Le Noë et al., 2017) allows to represent the mentioned compartments and their connections through material flows.

This study starts from the representation of the nitrogen (N) flows of the Spanish agro-food system for the years 1990 to 2015 (Rodríguez et al., 2022). N is considered an adequate component for the analysis because it is essential for crops, livestock and people as part of life-essential molecules, and if not embedded in food and feed, is a potential pollutant.

In addition, N, together with water, is the main limiting factor of crop production. But the relationship between N and water goes beyond crop production. Water availability through rain and irrigation significantly affects fertilizer use and nitrogen use efficiency of cropping systems. It also influences N deposition, N fixation, and finally, the net import/export of feed and food due to more demand or excess.

Climate change affects precipitation patterns (IPCC, 2022) and the frequency of dry/wet years, even if this variable exhibit higher uncertainty in comparison to other atmospheric variables. The N flows in the systems are expected to be different for dry and wet years, and therefore, different GRAFS can be depicted.

The mean accumulated precipitation (PP) in Spain was calculated from the E-OBS database (Cornes et al., 2018) for the 1990-2015 period. Then, dry (PP lower than 85% of mean P) and wet (PP larger than 115% of mean PP) years were identified. The hydrological years were considered (starting on October 1^st of the previous year until September 30^th).

Here, the projections from an ensemble of RCM climate models from the CORDEX project were selected for calculating the frequencies in dry/wet years for both near (around 2050) and far (around 2100) future periods.

Then, the frequency in dry, wet and normal years will be used for weighting the GRAFS from the present period to obtain the projected results, which will be analysed in terms of the impacts (e.g., production, external dependency, socioeconomic consequences). The discussion aims to provide insight of possible measures for adapting the Spanish agro-food system to future risks in response to the projected changes.

References

Cornes et al., 2018. Atmospheres, 123(17): 9391-9409.

IPCC, 2022. Climate Change 2022. Sixth Assessment. Cambridge University Press

Le Noë et al., 2017. Sci. Total Environ.,586:42-55.

Rodríguez et al., 2022. Proc. XXI International N Workshop. ISBN:978-84-122114-6-7