Microbiomes as Modulators of Human and Planetary Health: A Relational and Cross-Scale Perspective

The various human microbiomes play critical roles in maintaining health and well-being, and they are continuously shaped by a complex web of internal and external factors. Research on human and environmental microbiomes is generally discrete within disciplinary areas such as medicine, microbiology, molecular ecology, etc. This paper presents a perspective based on a scoping review of the literature, aiming to explore how these interconnected microbiomes shape human health and well-being and, in turn, planetary health. We explore the working of human microbiomes from cellular mechanisms to population outcomes, and the role of intrinsic and extrinsic factors influencing these microbiomes. We argue that global trends such as the homogenization of diets, environments, and medical practices are driving shifts in microbial diversity, with far-reaching implications for human health and well-being as well as planetary health. Disruptions to microbial feedback mechanisms at individual, community, and ecosystem levels are often interconnected and exacerbated by biodiversity loss and environmental change. We underscore the need for holistic public health interventions that account for microbiome stewardship across scales. By examining these connections, we aim to highlight the importance of a systems-level understanding of the microbiome in public health.