Can Supplemental Irrigation Alleviate the Effect of Climate Change On Wheat Production In Mediterranean Environments?.

The dry areas of the developing world occupy some 3 billion hectares. Crop growth under rain fed systems is limited by low amounts of precipitation, within season dry-spells and considerable year-to-year variability of precipitation. For the dry areas of the Mediterranean region, IPCC future climate projections show an increase in annual mean temperature and a decrease in annual rainfall. Increased evapotranspiration, less plant-available water in the soil, greater terminal heat stress and shorter growing seasons are predicted consequences, negatively impacting agricultural productivity. In this study we addressed the issue by simulating the impact of a (regionally downscaled) changing climate on wheat growth and yield under rainfed, Mediterranean conditions in northern Syria using the CropSyst cropping systems simulation model. Subsequently, we quantified possibilities of mitigating the negative impact of climate change by means of application of supplemental irrigation. Simulation results indicate that under climate change scenario SRES A2 for the period 2070 to 2100, wheat yield will decrease by an average of 10 % as compared to historic (1980-2010) conditions. Yield of straw, which is an important source of livestock feed in the region, will even drop by 23 %. Year to year variability of agricultural production will also be negatively affected. Simulations revealed that the percentage of years with yields below 0.5 t/ha will increase from historically 13 % (one out of eight years) to 27 % (one out of four years). Not surprisingly, given the fact that water is the most growth-limiting factor, supplemental irrigation could mitigate these negative impacts, in part by allowing for earlier planting of wheat and thus avoidance of (terminal) heat stress during grain filling period. However, as irrigation water resources are limited, policies on where to allocate water and how much, will have to be adapted in a climate change future. Growing summer crops under full irrigation might be a less viable option.