PhD Studentship: Lifting the ozone ceiling on Chinese crop production

China is particularly susceptible to the deleterious effects of air pollution on crops. The livelihoods of 450 million people in China depend directly upon agriculture and the country has a growing dependence on food imports. However, surface ozone concentrations in China are some of the highest in the world, routinely exceeding levels safe for plants. Past studies estimate that ozone decreases Chinese crop yields by more than 20%, costing about 3 billion USD per year, and imposing effective limits on agricultural productivity. Yet, the yield and financial losses are likely underestimated, as these studies did not consider that many cultivars grown in China have heightened sensitivity to ozone. Nor were they able to consider the timing of ozone exposure within the growing season, a crucial factor for accurate damage calculations. Effective mitigation of ozone damage will substantially increase and stabilise food production, but can only follow effective understanding.

Bringing together the disciplines of crop physiology and economics, this project tackles the Global Challenge of food security, with a focus on China. It will pioneer new modelling techniques to quantify how ozone pollution propagates into reduced agricultural production and explore measures to mitigate its impact.

The commonly adopted approach to calculate crop yield decline due to ozone exposure uses empirical relationships between surface ozone concentrations and observed yield losses, making the often-flawed assumption of a linear relationship between plant ozone exposure and uptake of ozone through leaf stomata. A more mechanistic approach is to relate crop yield losses to leaf ozone uptake, allowing accounting for interactions with other stresses and pollutants, such as drought or elevated levels of carbon dioxide. Such interactions are crucial for understanding the effects of timing of ozone exposure. Further, under global environmental change, the influence of these interactive effects is likely to be profound, mandating that they be accounted for before future impacts on agriculture can be adequately understood. The knowledge to carry out such a process-based quantification of ozone effects in China now exists, but the challenge of achieving it at the large scale, along with consideration of local crop cultivars and managements, has not yet been met. This is the next frontier in understanding, providing more insightful and accurate information for the development of effective mitigation strategies to enhance food security.

This PhD project builds on a ground-breaking new representation of ozone damage on wheat, developed within the vegetation model LPJ-GUESS. The model will be optimised and evaluated for major Chinese cereal crop cultivars, and the ozone damage functions extended to these crops. Combining this model with observational data, recent cereal production losses in China due to ozone will be calculated, thus quantifying the unrealised production potential achievable through alleviation of ozone pollution. Further, the extent to which high ozone pollution episodes have influenced interannual variability in crop production - a key aspect of food security - will be investigated. The student will work closely with partners at Peking University, who will provide expert knowledge on cropping systems and evaluation data.

Potential future impacts of ozone on Chinese agriculture will be assessed through scenario simulations, analysing the combined impacts of climate change and possible ozone-supressing adaptation options, and the resulting economic impacts calculated. The aim is to incorporate these results into an online tool (in Chinese), which can be used to explore the economic and food-security implications of policy options, providing a resource both for civil servants informing policy and for education. This translation of results will be carried out with partners at Peking and Nanjing. Project results are expected to lay groundwork for developing effective crop insurance schemes, and the approach developed will be broadly applicable across the wider region.

The project will draw on existing cross-college strengths in crop modelling, economics and food security at the University of Birmingham, and combine these with extensive local knowledge and insight from Chinese partners, providing both first-class scientific analysis, and a clear means of dissemination to stakeholders. The student will build strong connections in the international agricultural modelling community, along with knowledge and skills in quantitative modelling, crop physiology and economic analysis. Overall, this project will allow the student to pursue cutting-edge research that promises to make a significant contribution to understanding of how to develop more secure and resilient food production systems within China and the wider region, and thus deliver a substantial contribution to meeting the global challenge of sustainable agriculture and food security.