Written by: Ananya Mukherjee and Aditi Sudhir
55% of the world’s population currently lives in urban spaces, which is projected to increase to 68% by 2050. We already use 75% of the world’s resources, including food, water, and energy, and by 2030, two-thirds of the global population is projected to live in urban areas driven by rapid population growth, rural-to-urban migration, and the search for better economic opportunities and infrastructure. To meet this demand sustainably, our cities must evolve.
Several reports suggest that urban green spaces (UGSs) are crucial for both built environmental and societal well-being. These are natural or semi-natural spaces integrated into urban settings for recreational, ecological, or social purposes. UGSs vary across cities based on the types of vegetation—whether planted or naturally occurring—the species they support, the presence of water bodies, and the facilities available. They can be public, like parks, greenways, and community gardens, or private, such as backyards, residential gardens, society complexes, green roofs, and bioswales. While public spaces often serve broader community needs, private green spaces also play an important role in enhancing neighborhood biodiversity and individual well-being. Additionally, a limited but growing body of evidence shows how UGSs—both public and private—contribute significantly to physical and mental health.
UGSs provide habitats to animals, birds, and diverse above- and below-ground organisms, microbial and otherwise. Microbial communities usually include, but are not limited to, archaea, bacteria, fungi, algae and protists. However, we do not have a thorough understanding of the soil microbes by which we are surrounded. This is not trivial since “good microbes” can have a direct impact on human microbiomes, which affect immune health. In a world grappling with the effects of antimicrobial resistance, especially in the Global South, of which India is part, it has become vital to learn more about the microbes that surround us and what makes them tick.
The field of microbial ecology is slowly but steadily gaining traction globally due to its myriad applications, especially in human health. You may have heard of the “wood wide web,” a network of mutualistic fungi that interconnect several neighboring trees to obtain nutrients from each other. The diversity of fungi depends on the “health” of the forest or green space. Such networks help plants send each other warnings, enhance disease resistance and shuttle excess carbon to seedlings.
To make sense of the growing body of research, our research looked at numerous studies worldwide. This filtered out unreliable information, included only relevant studies and subjected them to multiple rounds of review to minimize bias.
This led to some fascinating and comprehensive findings. It revealed a gap in studies conducted around the equatorial regions, areas with high biodiversity. Tools like PCR have allowed scientists to identify the microbes present in the soil and correlate them to the plants found at the site. Many novel microbial families appeared for a handful of studies in the data, sparking curiosity about what might still be hidden in less-studied soils,a result that will have a profound impact on how we design our urban green spaces. Interestingly, most research has focused on public parks and forests, while areas like home gardens, playgrounds, and vacant lots are still largely unexplored.
Why does this matter for our health? Soil microbiomes are deeply intertwined with human biology. Exposure to diverse microbes—especially in early life—can strengthen our immune systems and may even reduce the risk of allergies, asthma, and autoimmune disorders. But aside from the physical, these green spaces and their microbial life may have a profound effect on our mental health as well. Studies show that spending time in biodiverse green spaces can reduce stress, anxiety, and depression. The microbes we encounter while digging in soil, walking barefoot on the grass, or even just breathing in the earthy air may help regulate mood by interacting with our gut microbiome and nervous system. Referred to by some researchers as the ‘old friends’ hypothesis, this idea suggests our bodies have long relied on soil microbes to help maintain immune and mental well-being.
So what can we do to retain and enrich the diversity of the soil microbiome? Actively sowing native plants in any available green space supports local ecosystems and microbial diversity. Educating ourselves about local vegetation is essential; understanding whether a plant is native or not helps us make informed decisions. Native species are not just beautiful; they have evolved alongside local microbes, wildlife, and climate, leading to deep-rooted relationships that support a richer soil life, more resilient ecosystems and even benefits to our health. By choosing native plants, we’re restoring a living, breathing network beneath our feet. Apps like PlantNet and iNaturalist provide extensive databases for plant identification, making it easier to choose
native species for our gardens. Using organic or natural fertilizers instead of chemical alternatives enhances soil health without disrupting microbial communities. Donning the caps of citizen naturalists or volunteers who help urban planners, nursery owners and architects, we can participate in community gardening and soil regeneration projects. Sustainable practices such as composting, responsible waste management, and water conservation promote a thriving soil microbiome and contribute to a healthier urban environment.
Disclaimer: Ananya Mukherjee is a faculty member and Aditi Sudhir is a research associate at Azim Premji University. The views and opinions expressed in this article are those of the authors and do not necessarily reflect the views or the positions of the organisation they represent.