I grew up in the Alps and I still live there. Mountains sit outside my window, forest behind the house. Work sends me into cities for days at a stretch, and the same pattern repeats every time.
I enjoy the first day. I sit in cafés and watch people, wonder whether a tree-lined street already counts as enough nature, then keep watching instead of deciding. People are everywhere in a city, and I want the stories behind them, which is what I miss at home: mostly open land, few people, long stretches of quiet.
By the second day something shifts, and it shows up in the body before it reaches the mind. I get restless and start looking for open space, wanting out of the narrowness. The feeling has always been there; the longer I pay attention to it, the clearer it becomes that it is not only mine.
Edward O. Wilson gave this feeling a name in 1984: biophilia, the innate human tendency to seek out living systems. The studies below confirm parts of that claim; other parts remain open. I went looking for the science because I wanted to understand what happens to me, and to other people, in cities, on open land, in rooms, in nature, more than because biophilia as a concept interested me.
I have watched people in both settings for years, not systematically, just paying attention. A group laughs together, unguarded. A man on a city footpath stares at his phone, packed in among strangers who are, like him, coming from somewhere and going somewhere else. Moods run from relaxed to worn out, and they vary enormously between individuals standing in the same place. I wanted to know whether any of that has evidence behind it. The answer was: partly.
What the studies measure
Roger Ulrich and colleagues put 120 subjects through a stress film in 1991, then showed half a nature video and half a city video (Journal of Environmental Psychology). They measured heart rate, muscle tension and skin conductance. Recovery was faster and more complete with nature. Within a few minutes heart rate fell to its lowest point since the stress film; with the city video it did not. I felt confirmed reading this one. I will probably never move to a city.
Terry Hartig and colleagues studied 112 subjects in 2003 (Journal of Environmental Psychology). The subjects first sat in a room, then walked for about 50 minutes, one group through a nature reserve, the other through a city. A room with a view of trees lowered blood pressure faster than a windowless room, and the nature walk produced greater blood-pressure recovery than the city walk.
Marc Berman and colleagues sent 38 students on a walk of about 50 minutes in 2008 and tested working memory before and after (Psychological Science). The nature walk improved scores by about 20 percent; the city walk produced no measurable gain. The result held regardless of mood, season or weather. In a second experiment, Berman and colleagues found that pictures of nature worked too; no actual walk was required. Confirmed again, I thought. My view out of the window is enough, even sitting inside at work.
Mikko Koivisto and Sara Grassini analysed 316 people in 2022, asking whether the positive response to nature is innate or learned (Journal of Environmental Psychology). Pictures of nature produced far more positive emotion than pictures of cities, regardless of childhood exposure to nature, age or gender. But tolerance for cities is learned: people who grew up close to nature find cities more unpleasant. That last part matches something I recognise in myself. People who grow up close to nature grow more sensitive to cities over time, not less.
It also marks where the studies stop answering my actual question. Koivisto and Grassini measure emotion, and emotion is not the state of consciousness I am trying to name. A person meditating in a park is not in the same state as a person jogging through the same park. Both are in nature. What the nature does to them depends on what they bring into it.
I have meditated since my early twenties and can shift my state of consciousness within minutes. Brain scans can register some of that too, but the context goes missing in the process: a scan returns a value, without the moment behind it.
None of this makes the studies wrong. I have no reason to doubt the data; the physiological effects are real, and the data behind them is solid. What I doubt is that measurement alone explains what a room does to a person. Two people can stand in the same room and go through something entirely different, shaped by their own history, their mood, the state they walked in with. I lack the terminology to put this more precisely, and other essays of mine take the question further.
I have spent time recently on ontology, and that work gave me a way to think about the gap: setting the existing measurements into a new relation with each other, between what a room measurably does and what a person brings that no instrument catches.
Photography helps here in a way data does not. A photograph holds the room and the person in the same frame at once, and that makes the space between them visible, the part the science leaves unanswered. Together with others who work on this closely, I co-founded the photo exhibition series Concrete Human (concretehuman.com) to show how much the built environment can do to people. I got here by way of Ann Sussman’s Cognitive Architecture: Designing for How We Respond to the Built Environment (Sussman & Hollander, 2015), which pulled me further into the studies, driven by wanting to understand my own responses to city, land, room and nature.
The dose
Mathew White and colleagues surveyed nearly 20,000 adults in England in 2019, asking how much nature a person needs in a week (Scientific Reports). Below 120 minutes, no measurable effect appeared. Above it, the likelihood of good health rose 59 percent and the likelihood of high wellbeing rose 23 percent. How the 120 minutes were spent did not matter: one two-hour visit, two one-hour visits or three 40-minute visits produced the same result.
Qing Li described a mechanism behind it in 2010 in Environmental Health and Preventive Medicine, working from shinrin-yoku, the Japanese practice of forest bathing. Trees release volatile organic compounds called phytoncides. These activate natural killer cells in the immune system, cells that destroy tumour cells, and the effect lasts at least 30 days after a single stay in the forest. Among nature people like me, forest bathing used to draw a smile. I think differently about it now, and it is on my list for its own essay.
White’s number is the one I keep coming back to: 120 minutes a week, a threshold below which nothing happens and above which health and wellbeing both measurably improve. Japan turned that finding into medical practice decades ago. My impression is that European and American health systems are still debating whether nature is good for people, while Japan already prescribes it.
The effects in these studies appear the same across income and education, which places the responsibility on planners and on the people who set budgets rather than on individual taste. Singapore is worth naming here: its population grew by two million people, and over the same period its share of green cover rose from 36 to 47 percent. Growing a city and keeping its nature did not have to be a trade-off there.