Assessment of Climate Change Impact on Rainfed Barley Production in the Mediterranean Basin : The Almeria province case study

Abstract: The Mediterranean basin is widely recognized as a climate change hotspot, with climate models projecting increasingly warmer and drier conditions that will impact local ecosystems, communities, and economies. Agriculture will be among the most affected sectors, with harsher conditions for crops’ growth, greater water needs, and lower yields. One of the most resilient crops to limiting and stressful conditions is barley, which is often sown in areas where other crops and cereals would struggle. This work analyzed the impacts of climate change on rainfed barley using the province of Almeria as a case study. This is one of the most arid areas of the Mediterranean basin, where agriculture is among the main economic resources, and where barley is the main crop produced outside greenhouses. Barley growth was modeled using the AquaCrop model in its Python implementation, AquaCrop-OSPy. Setting the model up to avoid local re-calibration of the barley parameters and to capture multi-year trends in productivity change, rather than its interannual variability. The study focused on two 30-year time periods: mid-century (2041-2070), and end-century (2071-2100); and on Shared Socioeconomic Pathways scenarios SSP1-2.6, SSP2-4.5, and SSP5-8.5. For each time period and SSP scenario, the research also evaluated three sub-scenarios of soil water content at sowing: with the parameter set respectively at 10%, 20%, and 30% of the Total Available Water (the water present in the soil available for the crop to sustain its life). Having estimated climate change impact, the research analyzed different adaptation pathways (irrigation, the application of mulches, and the change in sowing date), to evaluate their performances for climate change adaptation in the area.  The results indicate the importance of soil water content for maintaining good yields, or reducing losses, and indicate the possible average yield change to be between +14% and -45% at mid-century, and between +12% and -55% at end-century. The greater variability in productivity is associated with the soil water content at sowing rather than on the SSP scenario, with SSP5-8.5 being the only one showing a marked difference compared to the others. Regarding irrigation, the results show how with a soil water content at sowing of 10% of the Total Available Water, irrigation up to 100 m³/ha might not be sufficient to avoid productivity losses. Also, the study indicates that an optimal threshold to trigger irrigation for adaptation purposes might be found between 0% and 20% of the Total Available Water. Overall, it indicates how adaptation through irrigation can be viable in the province. The work moreover suggests the effectiveness of mulches as an adaptation strategy to partially limit irrigation water needs in the future and improve the yield performance of the crop. However, the research does not indicate a clear benefit linked to changing the sowing date to earlier or later sowing dates but suggests the importance of correctly seizing the sowing window to reach optimum yield in the future. Lastly, the work shows that the approach used to carry out this research is suitable to assess trends in yield change at multi-year scale, if the analyzed time window is indicatively larger or equal to 10 years, and if an error of around 10% on the results is accepted.