The past impact of climate change on the yield of major crops

Tuesday, 16 December 2014: 8:15 AM
Gen Sakurai1, Toshichika Iizumi1, Motoki Nishimori1, Masashi Okada1 and Masayuki Yokozawa2, (1)NIAES, Tsukuba, Japan, (2)Shizuoka University, Shizuoka, Japan
Understanding the relationship between climate change and crop production is of paramount importance for food security. Previous statistical analyses of historical data have revealed the important impact of temperature increases on past crop yields. However, the direct effect of the [CO2] increase, known as CO2 fertilization effect, is difficult to estimate by simple statistical analysis because the average atmospheric [CO2] does not vary widely over space and time. Moreover, it is also difficult to estimate each climatic effect on crop yields with completely removing correlation among climatic factors. Although non-statistical approaches using process-based crop models may overcome these problems, the results of simple simulation studies may be misleading because of the uncertainty of the model parameters.

In the present study, we applied a Bayesian statistical approach to estimate the parameters of a basic process–based model of crop growth (PRYSBI-2) and the past effect of each climatic factor on yields of major crops. The spatial variability of model parameters was considered by estimating the posterior distribution of the parameters from historical yield data by using the Markov-chain Monte Carlo (MCMC) method. The datasets of maize, soybean, rice, and wheat yields during 1982–2006 with a spatial resolution of 1.125° × 1.125° were used for this purpose (Iizumi et al. 2013). The posterior distributions of model parameters were estimated for each spatial grid with 30 000 MCMC steps of 7 chains. Using this model, we produced maps of the estimated past impact of each climatic factor (including CO2 effect) on crop yields (see Figure for the effect of temperature changes on maize yield as an example). The results suggested large variations of the impact of the change in average temperature on major crop yields. The results also suggested a large impact of CO2 increase on C3 crops such as soybean, rice, and wheat. In some regions, the positive impact of COincrease exceeded the negative impact of temperature increase. We also analyzed the impact of extreme climatic events on crop yields, and estimated hazard maps of these extreme climatic events.

Figure. The estimated impact of the change in average temperature during 1970–2000 on maize yield (%)