Climate mitigation sustains agricultural research and development expenditure returns for maize yield improvement in developing countries

Governmental expenditure on agricultural research and development (R&D) has played a substantial role in increasing crop yields in recent decades. However, studies suggest that annual yield growth rates would decline in a warming climate compared to that in a non-warming climate. Here, we present how projected climate could alter maize yield gain owing to a US$ 1 billion increase in agricultural R&D expenditure (referred to as yield response) for 71 maize-producing countries using global gridded crop model simulations with socioeconomic and climate scenarios as inputs. For the middle of this century (2041–2060) under the low warming scenario (shared socioeconomic pathways: SSP126), the median yield response between countries is estimated to be the highest at 27.2% in the low-income group, followed by 6.6% in the lower-middle-income group, 1.0% in the high-income group, and 0.1% in upper-middle-income group. The projected median yield response for lower (the low- and lower-middle)-income groups under the high warming scenario (SSP585) was approximately half than that under the low warming scenario: 27.2% → 15.6% for the low-income, 6.6% → 1.7% for the lower-middle-income, and 1.0% → 0.6% for the high-income groups. For the upper-middle-income group, where there is limited room for adopting high-yielding technology and management already being used in higher (the high- and higher-middle)-income groups, the negative impacts of climate change cannot be offset and yields are projected to decline, even with continued R&D investments (0.1% → –0.2%). Even if the R&D expenditures increase at the same value, expected yield gains will depend on future warming levels. This finding suggests that climate mitigation is a prerequisite for maintaining the yield returns from agricultural R&D investments in developing countries.