Crop Models Show Limited Accuracy Under Combined Climate Stresses, Study Finds
A new study published on bioRxiv evaluated two widely-used wheat crop models, APSIM and STICS, against real-world experimental data and found prediction errors as high as 123% under combined drought, heat, and elevated CO2 conditions. The models were tested using data from three Free-Air CO2 Enrichment (FACE) experiments across the USA, Germany, and Australia. The findings raise serious concerns about the reliability of current crop models used to assess future food security under climate change.
Researchers assessed the performance of two prominent wheat simulation models — APSIM and STICS — using data from three FACE experiments that combined elevated CO2, water deficit, and warming, conditions expected to become increasingly common under climate change. A key methodological finding was that supposed 'control' conditions in the experiments already contained hidden heat and water stress, meaning the models were calibrated on crops that were already physiologically stressed. Prediction accuracy degraded sharply as stress complexity increased: errors ranged from just 3–9% under unlimited conditions, to 4–27% under single-stress conditions, to 17–123% under combined stresses. Elevated CO2 further compounded uncertainty, particularly when crops were simultaneously experiencing water stress. The authors conclude that current stress response functions in both models fail to capture the synergistic interactions between drought and heat, and call for more mechanistic modelling approaches to improve the credibility of climate impact assessments for agriculture.
What's missing
The analysis is restricted to wheat and three specific FACE experimental sites, so generalisability to other crops, geographies, and stress combinations is uncertain. The study does not propose or test alternative modelling frameworks that might address the identified gaps, leaving open the question of how improvements should be implemented.
What different sources said
- bioRxivCenter
Evaluating crop models for future climate scenarios: wheat yield predictions using APSIM and STICS under combined CO2, warming, and water deficit conditions
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