Assessing Climatic Vulnerability and Projecting Fine Rice Productivity Using DSSAT Model.

Pakistan is among the most vulnerable countries to climate change. The relationship between climatic changes and agriculture is particularly an emerging issue, as the world’s food production resources are already under pressure due to agressively increasing population. Crop Growth and Global Circulation Models (GCMs) are helpful tools to quantify the climate change and its impact on crop production. These tools has helped in decision making as well as in the development of adaptation strategies for the policy makers, researchers, farmers and businessmen. The rice zone of Punjab-Pakistan was selected to evaluate the impact of climate variability on yield of fine rice farms under semi-arid conditions using Decision Support System for Agro-technology Transfer (DSSAT). After calibration and evaluation of model with two years experimental data, the DSSAT model was run with 155 farms data taken through modified strata sampling technique from all strata of rice zone. Early (2010-2039), Mid (2040-2069) and Late (2070-2100) century climate change scenarios were developed by Pakistan Meteorological Department (PMD) using GCM, CCSM4 with RCP 4.5 and RCP 8.5 scenarios over baseline (thirty years observed data) 1981-2010 weather. These predicted scenarios weather data were with maximum and minimum temperature, rainfall, solar radiations and carbon dioxide concentration. The observed and simulated yield of farmers per hectare was compared by using the observed weather data of rice-zone in model  for evaluation of DSSAT to take this simulation as a baseline. The results of model evaluation were with R² (0.61), d-stat (0.78) and RMCE (510.77). Simulated data of model at different climate scenarios were taken per year per hectare basis. The average yield of 155 farms was 4078 kg ha^-1 of rice zone. The yield of different climate scenarios with RCP 4.5 and 8.5 in the Early, Mid and End of century was 3603, 3327, 2958, 3411, 2674 and 2333 kg ha^-1 respectively. The percentage reduction of yield with RCP 4.5 in Early, Mid and End of century was 12%, 18%, and 27% as compared to baseline and RCP 8.5 at same time periods showed 16%, 34% and 43% reduction in yield per hectare. From these simulations and analysis, it was concluded that to ensure food security with increasing population, we have to uplift our paddy production through adaptations (direct seeding, planting time, high input efficiency and genetic upgradation) in short-run and mitigations (minimum methane and N₂O emissions)in the long-run.