What would happen to barley production in Finland if global warming exceeded 4°C? A model-based assessment

In research to date, projected climate change has been considered to be beneficial for agriculture under Nordic conditions, where crop production is mainly limited by low temperatures resulting in short growing seasons. However, with the rapid increases in global mean temperature implied at the high end of the uncertainty range of current projections, which are typically amplified at high latitudes, conditions for crop production could change so dramatically that yields would be reduced, even accounting for the positive effects of CO2 fertilization. In this study, we used the WOFOST crop growth simulation model to examine crop yield responses to a set of plausible scenarios of climate change for Finland up to 2100, including some that exceed 4 °C global mean temperature increase relative to pre-industrial. We selected spring barley (Hordeum vulgare L.) as an indicator crop and calculated water-limited yields for two Finnish locations, Jokioinen and Jyväskylä and for a clay and a sandy soil. Scenarios included systematic increases in temperatures, changes in precipitation distribution and altered daily climatic variability using the M&Rfi weather generator. We also examined the effectiveness of a few adaptation options, such as shifts in sowing dates and hypothetical new crop cultivars. Increasing temperature reduced total growth duration and yield considerably, even with adjusted earlier sowing. A reduced number of rainy days had marked negative effects only in combination with increases in temperature of 4 °C or greater, leading to distinctly higher yield losses on the sandy soil than on the clay. Prolonged dry spells clearly increased yield variability. For scenarios with temperature increases of +6 °C and + 7°C, yield losses at Jokioinen were highest; losses at Jyväskylä were generally less pronounced. Neither CO2 fertilization nor adjusted sowing could compensate the yield losses from temperature changes exceeding +4 °C. On clay soils, yield loss could be compensated by new cultivars. For sandy soils even with new cultivars, there would be yield loss at temperature increases exceeding +3 °C. It can be concluded that the positive effects of climate warming and elevated CO2 concentrations on cereal production at high latitudes are likely to be reversed at temperature increases exceeding 4 °C, with a high risk of marked yield loss. Only plant breeding efforts aimed at increasing yield potential jointly with drought resistance and adjusted agronomic practices, such as sowing, and adequate nitrogen fertilizer management and plant protection, holds a prospect of partly restoring yield levels and reducing the risks of yield shortfall.