Assessing the Impact of Climate Change on Agriculture in Hamedan-Bahar Plain with Emphasis on Water Productivity and Food Security

The potential impacts of climate change on water resources and food security are receiving growing attention especially in regions that face growing challenges like water demands for agricultural, domestic and environmental uses. The anticipated climate change are likely to impact water resources (surface water and groundwater) by altering precipitation patterns and change in nature of rainfall regimes. Apart from the effects on water availability, climate change is expected to adversely affect crop productivity, food security and food producers' income. Climate changes could affect the four dimensions of food security; food availability, access, utilization, and stability. Therefore, this study aims at investigating the economic effects of climate change on the agricultural sector (including the yield of crops, water resources, food security and profitability) in Hamadan-Bahar plain. The hypothesis tested in this research is that climate change has negative impacts on the agricultural sector in the study area and it is necessary to present solutions to reduce these effects. Accordingly, the question answered in this study is whether climate changes in the region reduces crop yields, the profitability of the agricultural sector, and aggravate the scarcity of water resources. For this purpose in this study, the effects of climate change in different scenarios on regional cultivation pattern, basic food cultivation pattern, gross profit of farmers, physical and economic productivity of water and food security in Hamedan-Bahar plain have been investigated and then various suggestions to these problems have been presented.

For this purpose, the physiological, hydrological and meteorological aspects of the problem were integrated into an economic model and the changes in cultivation pattern of the plain were projected in counterfactual climatic scenarios. Accordingly, the outputs of the HadCM3 model under the scenarios of B1 (optimistic) and A2 (pessimistic) were utilized for the fourth report; additionally, the outputs of the ensemble model under RCP 2.6 (optimistic) and RCP 8.5 (pessimistic) scenarios were used for the fifth report of IPCC. Then, the variables of rainfall and temperature for the horizon of 2070 were predicted under scenarios B1, A2, RCP2.6 and RCP8.5 using the Lars-WG model. In this regard, the yield response functions of the products with respect to climatic parameters by the Generalized Maximum Entropy method (GME) were estimated and the elasticity of the yield of the products with regard to temperature and rainfall were calculated. Then products yield changes on the 2070 horizon under different climate change scenarios were predicted and by including it in a positive mathematical programming (PMP), the impact of different climate change scenarios on regional cultivation pattern, basic food cultivation pattern, gross profit of farmers, physical and economic productivity of water and food security were examined. To estimate the yield response regression model and predict climate changes by LARS_WG model, the data on the period 1982-1982 were used. Also the data and information of farmers were obtained using a two-stage cluster sampling method in 2018 (baseline).

The results indicate an increase in temperature, a decrease in precipitation, a decrease in the supply of water resources, and consequently a decrease in the yield of most basic food products and an increase in the yield of some vegetable and summer crops were anticipated in all scenarios. The results also showed that the occurrence of the mentioned consequences has negative effects on the total production of crops, the amount of production of basic food products and the gross profit of farmers in the region. And in this regard, in the most pessimistic scenario on the horizon of 2070, it will impose a loss of 490 billion rials on farmers. The increase in the physical and economic efficiency of water in different scenarios shows that water is becoming more valuable due to the decrease in the quantity of water due to climate change. Therefore the economic value of water would increase in the future decades in Hamadan-Bahar plain, which itself represents the severity of water scarcity in the agricultural sector.

The occurrence of climate change by affecting water resources, crop yields, cultivated area, food production and ultimately farmers' incomes, in addition to imposing economic and environmental losses, would affect various aspects of food security such as food availability, access, stability and utilization. Accordingly, in order to maintain and improve the yield of crops and reduce the possible losses imposed on income and food security of the region, it is vital to adopt appropriate strategies compatible with climate change, including the use of new irrigation technologies, deficit irrigation methods and to reform the cultivation pattern by selecting products with higher economic value in order that increase water productivity. Finally improving management of water resources and farmers' income at the plant, farm and region levels, is crucial.