Current warming will reduce yields unless maize breeding and seed systems adapt immediately

Abstract

The development of crop varieties that are better suited to new climatic conditions is vital for future food production 1,2 . Increases in mean temperature accelerate crop development, resulting in shorter crop durations and reduced time to accumulate biomass and yield 3,4 . The process of breeding, delivery and adoption (BDA) of new maize varieties can take up to 30 years. Here, we assess for the first time the implications of warming during the BDA process by using five bias-corrected global climate models and four representative concentration pathways with realistic scenarios of maize BDA times in Africa. The results show that the projected di erence in temperature between the start and end of the maize BDA cycle results in shorter crop durations that are outside current variability. Both adaptation and mitigation can reduce duration loss. In particular, climate projections have the potential to provide target elevated temperatures for breeding. Whilst options for reducing BDA time are highly context dependent, common threads include improved recording and sharing of data across regions for the whole BDA cycle, streamlining of regulation, and capacity building. Finally, we show that the results have implications for maize across the tropics, where similar shortening of duration is projected.By 2050 the majority of African countries will have significant experience of novel climates 1 . However, precise information as to when novel climates will occur has not been available until the recent development of techniques to identify the time of emergence of climate change signals 5,6 . These techniques quantify the signal of a change in climate relative to the background 'noise' of current climate variability. Metrics that capture the response of crops to single or multiple aspects of weather or climate (crop-climate indices 7 ) are another tool that has been developed intensively in recent years. Alongside crop yield modelling, these techniques now enable assessments of the projected times at which climate change will alter crop productivity. These alterations are mediated through both crop growth (that is, photosynthesis and biomass accumulation) and development (phenological and morphological responses).We use seven crop-climate indices (Supplementary Table S2) to identify when heat stress, drought stress and crop duration (that is, time from germination to maturity) become systematically and significantly outside the ranges at present experienced by maize cultivation in sub-Saharan Africa. Crop breeders have long been aware of the need to develop new crop varieties that are suited to future climates, particularly with respect to heat and drought stress 8,9 . Heat stress impacts are evident in our analysis. However, heat stress indices are not sufficiently constrained at present (that is, uncertainty in their values is too great) for detection of a climate change signal; only the signal in crop duration changes exceeded the noise of climate variability and thus showed a time of emergence within this century (see...

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