The impact of climate change on the production of wheat in Lebanon -

Abstract

Climate extreme indices were calculated for the Beqaa Valley, Lebanon using weather data that was collected, digitized and cleaned for the first time from the American University of Beirut Agricultural Research and Education Center for the period 1956-2013. The indices were calculated using the RClimDex software which was developed by Xuebin Zhang and Yang Feng as part of an international initiative to develop and analyze a suite of climate extreme indices. Linear trends were computed using the Theil-Sen estimator which has been widely used in climatic and hydro-meteorological series. Results, although mostly not statistically significant, were in line with trends obtained in previous literature for the Middle East and Lebanon. The growing season length index showed a significant and decreasing trend which can potentially limit the growth of wheat and other crops. A positive trend was noted in the annual count of summer days and tropical nights. Cool days and nights decreased, warm days and nights increased and the cold spell duration index showed a decreasing trend. An increasing but weak trend was observed for all precipitation indices (though not statistically significant). To further explore the impact of this change in climate and its impact on wheat production, the relationship between wheat yields and three monthly climatic variables (maximum temperature, minimum temperature and precipitation) was evaluated for Lebanon for the period 1961-2008. A series of independent regressions was performed between technology-adjusted residuals and monthly climatic variables. Results of multiple regressions showed that the maximum temperature for March has a high and statistically significant negative effect on yields. The logged precipitation for April and logged precipitation squared for November also showed a significant positive effect and are in line with winter wheat growth stages and water requirements. The above results should be considered in the larger context where as much as 50-80percent of wheat grown in