When Bridget Chalifour set out to study something most of us never think about—the microscopic world living inside our noses—she discovered a surprising truth: the bacteria there are listening to our choices, responding to how much time we spend in nature. Her team at Denver's Museum of Nature & Science enlisted 111 museumgoers to contribute nasal swabs and answer questions about their mental health, outdoor time, and green space exposure. What they found bridges a gap that researchers had largely overlooked: the connection between what lives in our nasal microbiome, how much nature we experience, and how we feel.
The work matters because understanding these connections could reshape how we think about mental health and prevention. Scientists already know that exposure to nature correlates with better cognitive function, lower blood pressure, and improved mental well-being. Previous studies have also linked the human microbiome to time spent outside. But the nasal microbiome—that specific collection of microbes living in our noses—had remained largely unexplored in this context. Chalifour's team closed that gap using 16S rRNA sequencing to catalog the nasal microbiomes of participants, then cross-referenced their addresses with publicly available satellite data to map green space in their neighborhoods.
The results were illuminating. People who lived around more vegetation hosted a wider variety of microbes in their noses, with specific bacterial signatures shifting depending on the greenery nearby. But here's what makes the finding truly striking: the nasal microbiome doesn't just passively reflect our environment. The same microbes that correlated with more time spent outdoors were also associated with better mental health scores. "We tend to associate greater diversity and greater richness with a healthier microbiome," Chalifour said, and the data suggested that diversity in the nasal microbiome appeared to track with improved well-being.
Perhaps more intriguingly, time spent outside proved to be an even stronger predictor than green space itself. People who spent more time outdoors, regardless of how vegetation-dense their surroundings were, reported lower depressive scores overall. The distinction matters: it suggests that the act of being outside—moving through nature, breathing different air—carries benefits that go beyond simply living near parks. And remarkably, the microbiome appears to be the conduit. "People are changing their microbiomes just by spending more time in nature," Chalifour noted, implying that the bacteria in our noses may actively facilitate the mental health improvements we experience when we step outside.
The study represents a first foray into microbiology for the Denver Museum of Nature & Science, though the institution has long maintained a robust tradition of scientific inquiry across fields. Chalifour presented these preliminary findings at ASM Microbe 2026 in Washington, DC. The research opens new questions: Could deliberate time in nature become a recognized intervention for mental health? Might understanding our nasal microbiomes help us personalize approaches to well-being? For now, the data offers something simpler and more hopeful—evidence that our bodies are designed to thrive when we spend time in the natural world, and that even at the microscopic level, we're wired to respond to the call of green spaces.