Nearly all organic material on Earth is produced by photosynthesizing organisms that play a critical role in food web dynamics, providing the energy needed to sustain consumers at higher trophic levels, including humans. Studies conducted with chemistry-climate models suggest that the firestorms associated with a potential nuclear conflict destroy the protective stratospheric ozone layer, exposing critical photosynthesizers to high levels of UV radiation. Despite the potentially devastating impacts, few studies have investigated the effects of postnuclear UV radiation perturbations on terrestrial and marine photosynthesizers. In this project, we will use a state-of-the-art Earth system model to simulate the response of terrestrial and marine primary production to postnuclear UV radiation. We will modify an existing model to include parameterizations for damage by UV radiation for different types of crops, plants, and marine phytoplankton. We aim to conduct multiple simulations with the modified model to produce a detailed quantification of the sensitivity of photosynthesizers to postnuclear UV radiation and to assess the potential for cascading impacts of nuclear conflict on ecosystem integrity and food security.