Crop production modelling under climate change and regional adaptation

Climate change has the potential to profoundly affect agricultural production in Australia. Previous studies have identified that, in general, most agricultural regions in South-East Queensland are likely to have reduced water availability in the future due to likely decreases in rainfall, changes in temperature and net evaporation. These effects are then likely to exacerbate other climate-related crop production challenges through fruit loss, lower yields and reduced water use efficiencies due to higher temperatures. The aim of this project is to provide a detailed biophysical and economic assessment of identified adaptation strategies, potential implications and adaptation potential under different climate change (CC) scenarios for the Queensland cropping industry. This project conducted focussed reviews on the adaptation strategies at the regional and national scales for grain and sugar cane industries, and on how the impact of elevated CO2 is modelled into the selected crop models in order to assess the effect of CO2 enrichment on the study crops. An multi-model ensemble approach (as developed in DCAP USQ 7.2) was used to simulated crop yields under 3 different CC scenarios and some of the adaptation strategies suggested after consultation with growers and industry experts. The economic modelling involves (1) assigning a dollar value to every event in crop models, such as sowing and harvest, and other operations on farm, and (ii) quantifying the annual profit according to the strategy. The reviews of literature identified that many potential adaptation strategies are common across industries. Thus, technical adaptation options such as changed sowing/planting dates, use of long-maturing and/or drought-tolerant varieties, improved management of limited water supplies, improvement of field-drainage, improved decision making regarding herbicide, pesticide or fertilizer application, switch between crops or between cropping and livestock production, and switch land to non-agricultural use or bring new land into production, are among the common strategies at field and farm levels. At the regional level, since there will be wide variation in CC impacts across the growing regions, regional studies to detail the effects of all limiting factors of crop yield including moisture, temperature, nitrogen, and phosphorus are needed. A range of potential adaptations also exists. They include institutional changes, industry capacity development programs, regional development policies, drought support programs, rural adjustment and trade, flexible R&D, etc. Engagement with some key stakeholders was carried out through interviews and meetings. Overall, for agriculture in drylands, farmers have a conservative behaviour which consist to minimizing costs and ensure minimum incomes when adverse weather conditions. The adaptation strategies mentioned include changes in sowing/planting dates, management practices that help keep the soil moisture as long as possible throughout the cropping season, adoption of new crop varieties (e.g., heat/drought, and/or pest and disease tolerant cultivars), efficient use of chemicals and fertilizers through precision agriculture, and the use of decision support tools integrating information about climate and key crop management practices. The multi-model ensemble approach (including the models APSIM and DSSAT) was used for assessing some adaptation strategies to CC at field level. The study crops were wheat, sorghum, cotton and sugarcane. Simulations results using projected climate data from the HADGEM2-ES general circulation model forced with three representative concentrations pathways (RCPs) 2.6, 4.5 and 8.5 showed variable and relatively important yield decreases according to the site and crop over the 2030-2099 period. The economic analysis indicates that without adaptation overall gross margins will decrease. Successful adaptation to climate change will need both strategic preparation and tactical response strategies. One of the benefits of farming in a region historically prone to significant annual and seasonal climate variability is that producers have relatively high levels of diversification. This may well enable them to consider adaptation options with greater ease compared with farmers who have not had to incorporate strategies to overcome climate variability.