A review of crop water productivity in the Mediterranean basin under a changing climate: Wheat and barley as test cases

The ever-increasing water demands in the agricultural sector of the Mediterranean basin region (MBR) under climate change warrants that crop water productivity (WP) is a relevant topic for discussion. Considering this need, this study aims to synthesize the body of knowledge on WP focusing on the MBR. The study is based on two test cases: (1) wheat, because it is a basic staple food in high dietary demand in the region and (2) barley, because it is a climate-resilient alternative that is extensively cultivated in severe water- and salinity-stress conditions. These staple crops are strategically important for regional food security in the MBR, which covers southern Europe, North Africa and western Asia. The study tries to investigate the plausible reasons for yield and WP gaps in the region. Our meta-analysis revealed that wheat and barley are very different in their spatial distributions, productions and stress resiliencies in the MBR. Under the large gamut of biophysical and socio-economic constraints that affect crop production, it is observed that the northern and southern parts of the MBR have large capacity differences (institutional, infrastructural and technical) in cereal production. It is noted that the role of soil-water management in improving WP is vital and plays a critical role in closing yield gaps across the MBR. Moreover, the scaling of stress-tolerant varieties along with a package of agronomic practices can enhance WP, and thereby we can make the region adaptive to climate change, especially in terms of water stress. The literature revealed that the MBR, especially the southern parts encompassing North Africa and western Asia, critically lacks comprehensive experimental/observational evidence on the dynamics of field water balance. This knowledge is key to enhancing WP assessments using modelling approaches. The paper concludes that the MBR does have water-saving potential; it simply needs planned adaptation measures to enhance WP at the local and regional scales with effective benchmark studies in future.