Cities around the world are increasingly incorporating nature-based solutions, also called urban ecological infrastructure or blue-green infrastructure, for their multiple benefits. Urban agriculture is increasingly being framed as a nature-based solution because of posited social (e.g., community building and food security), health (e.g. reducing stress, improving mental health and cardiometabolic outcomes), and ecological (e.g. greening and nutrient recycling) benefits. Agriculture, in the city or in rural areas, dramatically affects water flows as well as nutrient cycling, particularly nitrogen and phosphorus. In an urban context, agriculture can be in a privileged position to increase circular nutrient flows by reusing organic waste streams such as food and plant waste to meet crop nutrient needs. In other words, compost applied to urban farms and gardens creates opportunities to recycle waste nutrients back into the human food system. These compost-rich garden soils may have high infiltration rates contributing to stormwater retention, and gardens may have high evapotranspiration rates helping to mitigate urban heat island effects. However, over-application of nutrients in urban gardens can also result in nutrient export through leachate and runoff, which in turn has the potential to lead to eutrophication and harmful algal blooms with implications for ecological and human health. The potential ecological benefits and drawbacks of urban agriculture related to organic waste and water management are not clear-cut. This session will draw on field work, literature review, and modelling work to explore how urban agriculture in different cities contributes to organic material recycling and the delivery (or retention) of nutrients and other substances towards waterways. We will also explore how urban agriculture as a nature-based solution interacts with public health outcomes.