Millions of smallholders in the Global South depend on maize, largely cultivated under rainfed conditions, for their own food security and livelihoods. Climate change mediated weather extremes, such as heat waves and frequent droughts, pose a major challenge to agricultural production, especially for rainfed crops like maize in the tropics.
“With both effects coming together under heat stress conditions, plants are surrounded, with no relief from the soil or the air,” said Pervez H. Zaidi, maize physiologist with CIMMYT’s Global Maize Program in Asia. “Climate change induced drought and heat stress results in a double-sided water deficit: supply-side drought due to depleted moisture in soils, and demand-side drought with decreased moisture in the surface air. “
Extreme weather events
Weather extremes have emerged as the major factor contributing to low productivity of the rainfed system in lowland tropics. South Asia is already experiencing soaring high temperatures (≥40◦C), at least 5◦C above the threshold limit for tropical maize and increased frequency of drought stress.
“In today’s warmer and drier climate, unless farmers have copious amounts of water (which might not be a sustainable choice for smallholders in the tropics) to not only meet the increased transpiration needs of the plants but also for increased evaporation to maintain necessary levels of humidity in the air, the climate change mediated weather extremes, such as heat and drought pose a major challenge to agricultural production, especially for rainfed crops like maize in lowland tropics,” said Zaidi.
To deal with emerging trends of unpredictable weather patterns with an increased number of warmer and drier days, new maize cultivars must combine high yield potential with tolerance to heat stress.
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