Drought stress impacts of climate change on rainfed rice in South Asia

Rice production is threatened by climate change and the productivity of rainfed rice is increasingly challenged. A better understanding of the future trends of rice production associated with climate change is important for improving food security. Rice production under irrigated and rainfed conditions was simulated using the rice crop model ORYZA2000. Simulated rice yield representing crop and environment interaction was used to evaluate the drought impact of climate change on rainfed rice in South Asia. If rainfed rice system was applied in all current rice cultivating areas in South Asia, drought stress could result to yield losses of more than 80 in 22 %, but crop failure was lower than 40 in 73 % of the areas under mild and severe SRES A1B and A2. The spatial patterns of drought stress on rainfed rice were similar under both A1B and A2, and the yield loss and crop failure decreased slightly in the far future (2045 to 2074) in areas where drought risk was high in the near future (2015 to 2044), but the impacts would gradually increase over initially low-impact areas. Both A1B and A2 would shift the best sowing season of rainfed rice to be earlier or later by up to 90 days in 30 years. Appropriate adjustment of sowing season is a major adaptation strategy for rainfed rice production in South Asia to benefit from climate change. In this case, rainfed rice yield could potentially increase by about 10 % in most areas of South Asia associated with 10 to 50 % lower inter-annual variation and slightly higher risk for crop failure.

气候变化正对水稻生产构成威胁，雨养水稻的生产力也正面临日益严峻的挑战。深入理解气候变化背景下水稻生产的未来趋势，对保障粮食安全具有重要意义。本研究采用水稻作物模型ORYZA2000，对灌溉与雨养条件下的水稻生产状况开展了模拟。以表征作物与环境交互作用的模拟水稻产量为评估指标，本研究分析了气候变化引发的干旱对南亚雨养水稻的影响。若将雨养水稻种植体系应用于南亚当前所有水稻种植区域，在SRES（排放情景特别报告，Special Report on Emissions Scenarios）A1B与A2两种情景的温和、严重情境下，22%的区域将因干旱胁迫遭受超过80%的产量损失，而73%的区域作物绝收率低于40%。A1B与A2情景下，干旱胁迫对南亚雨养水稻的空间分布特征基本一致；在2015-2044年近期干旱风险较高的区域，2045-2074年远期的产量损失与作物绝收率均小幅下降，但在原本受干旱影响较低的区域，其影响将逐渐加剧。在30年的时间尺度下，A1B与A2情景均会使雨养水稻的最佳播期提前或延后最多90天。合理调整播期是南亚雨养水稻生产适应气候变化、从中获益的核心应对策略。在此策略下，南亚大部分区域的雨养水稻产量有望提升约10%，同时年际波动降低10%-50%，但作物绝收风险将小幅上升。