Supporting urban greenspace with microbial symbiosis

Societal Impact Statement: Cities are stressful environments for plants, plagued by heat, pollution, and biodiversity loss. As a result, plant communities tend to suffer in green roofs, parks, and living walls. Finding solutions to help plants grow in stressful environments is a goal of the sustainable city. One solution is to better incorporate plant–microbe symbiosis in green architecture. Symbiotic fungi and bacteria can provide nutrients, water, and help plants to cope with urban stress. The reconceptualization of green infrastructure from a microbial-focused perspective has the potential to improve plant health, growth, and diversity in cities. Summary: Plant communities in cities help maintain the health and stability of urban ecosystems and inhabitants. Ensuring that greenspace is healthy and productive is a key goal of green infrastructure and landscape architecture (GILA). However, cities are stressful environments for plants. In natural ecosystems, plants live in symbiosis with fungi, bacteria, and other microbes that can help alleviate stress. Microbial communities may also help with stress associated with urban environments. Incorporating mutualistic symbioses into GILA is a sustainable way to enhance urban greenspace. Here, we address key stressors for GILA in cities, including dependency on fertilizers, pathogens, drought, fewer pollinators, pollution, and reduced plant biodiversity. For each of these stressors, we discuss how symbiotic fungi and bacteria can help mitigate these issues, including case-use scenarios. We conclude with new approaches to deliberately incorporate mutualisms in cities and open dialogues with stakeholders.