ASSESSING CLIMATE CHANGE IMPACTS ON CROP YIELD: A CASE OF TULSIPUR, DANG

Abstract

Climate change has created a serious concern for food security, extreme hydrological conditions, environment, ecology, health, and even entire human civilization. A developing country like Nepal is even more vulnerable to climate change impacts due to our weak infrastructure. Climate change is projected to have devastating impacts on crop yield. This study aims to assess the impacts of climate change on crop water requirements and crop yield in Tulsipur, Dang. It also aims to aid climate research in Nepal by the development of climate information system and projection of future climate in the region using Global Climate Models (GCMs). Temperature and precipitation data from stations all over Nepal were acquired in a gridded format by Kriging with External Drift (KED) interpolation. For the projection of future data, five CMIP6 based GCM models were used, and bias corrected to form an ensemble. Future climatic data was obtained under two Shared Socioeconomic Pathways Scenarios (SSPs): SSP245 and SSP585. The multi-model ensemble (MME) approach was used to minimize uncertainty associated with model predictions, and GCMs proposed were selected. The quantile mapping (QM) method was used for correcting the biases in the GCMs, and the RQUANT method was chosen for rainfall data, while the ‘PTF: linear method’ was used for temperature data. A crop simulation model (AquaCrop) was calibrated and validated using cultivar-specific and less conservative parameters obtained from farmer surveys, input climatic daily data, and soil properties. The calibrated model was then used to predict future crop yield scenarios for rice and wheat under different irrigation strategies and fertility stress levels. The data acquired from the climate information system has shown a good fit (R2 = 0.913) with nearby station data in Tulsipur and hence shows promising utility in replacing station data as starting point for future climate studies. Additionally, climate projection studies show that Dang is expected to experience progressive warming and increased rainfall in future (2021-2100). Wet seasons are projected to continue receiving more rainfall and rising temperatures which is likely to induce extreme events such as flooding. Conversely, dry winter seasons are likely to be drier and hotter in the future, which is detrimental to winter crops. The results of our study show a positive response of crop yield to climate change. Rice yield is projected to increase by as much as 112% by 2100 under extreme carbon emission scenarios. Similarly, wheat yield is projected to increase as much as 165% under similar ideal conditions. On the other hand, crop water requirements are projected to increase for both rice and wheat. The study also provides useful information for climate change adaptation and mitigation strategies in Nepal and recommends further research to improve the accuracy and reliability of crop simulation.