Assessing the impact of a warmer and drier climate on Swedish annual crops

We assessed the effects of temperature increase and variation in precipitation on the growth and development of four crops (barley, forage maize, oats and spring wheat) in five locations in Sweden (Kristianstad, Farjestaden, Lidkoping, Uppsala and Umea) using the process-based crop model APSIM. Baseline simulations were run for each crop and location, with weather data for 1980 to 2005 obtained from the CCAFS dataset. Synthetic climate data were defined using the baseline climate with (i) incremental increases in daily minimum and maximum temperatures and CO2 concentrations, combined with (ii) incremental increases and decreases in daily precipitation. Future climate simulations were then run using 26 years of synthetic climate data and compared with baseline climate in terms of changes in (i) crop productivity (grain yield for barley, oats and spring wheat, aboveground dry matter yield for forage maize) and (ii) risk of crop failure. Baseline results are consistent with the expected productivity in farmer fields for each crop. Considering the effects of climate change on the yield, the results suggest that crops will behave differently depending on the location and magnitude of changes in temperature. Barley and oats showed a maximum increase in yield with a 1°C increase in temperature. The same trend was observed for spring wheat, with the exception of Umea, where the maximum yield was obtained for a 4°C increase in temperature. Forage maize showed better performances for greater temperature increases (2-3°C) in all locations, with the exception of Umea, where the maximum simulated yield is reached for a 5°C increase. There is little effect of changes in precipitation on the productivity of the crops. Results suggest that, in the case of a high increase of temperature (+5° C) and decrease of precipitation (-20%), forage maize production should increase for all locations, whereas oats production should decrease for all locations. Barley and spring wheat should have a decrease in production, with the exception of Uppsala (barley) and Umea (spring wheat). Risks of crop failure computed from simulations showed a different pattern, with all crops being little impacted by changes in climate, with the exception of Umea where forage maize and, to a lesser extent, oats and spring wheat showed decreasing risk of failure with increasing temperatures. Although some simplifications had to be made to parameterize the model and prepare the synthetic climate data, the current results provide a useful projection of potential trends in production of crops in Sweden, and are similar to results obtained in other studies in the Nordic region. This study underlines several research questions that need to be addressed to better understand the effects of drought and, more generally, of climate change on annual crop production. Continual development of improved crop models (e.g. including a dynamic link between water use efficiency and CO2 increases) is necessary to better understand the dynamics of crop production and increase prediction accuracy in changing climates. Effects of N-fertilization on mitigating the negative effects of temperature also need to be investigated. Finally, defining priority traits of ideal cultivars to reduce the negative effects of climate change is an important upcoming task.