How much exposure to nature is needed to improve physical and mental health? This is a question that the Biophilic Cities Project and other researchers are trying to answer. Roger Ulrich’s landmark study in 1984 investigated whether recovering gallbladder surgery patients who were assigned a room with a window view of nature saw beneficial results (Ulrich, 1984). The results showed that patients with window views of trees had shorter hospital stays, fewer negative nurses evaluation comments, and took fewer moderate and strong pain-relieving drugs.

Since then other researchers have tried to answer various questions regarding nature’s impact on wellness. Researchers at the University of Illinois at Urbana-Champaign released results from their small study that showed being in nature for a certain amount of time worked as well or better than a dose of medication on children with Attention Deficit Hyperactivity Disorder (ADHD) (Parker-Pope, 2008). Other researchers have shown other benefits of nature, such as its positive impact on our levels of generosity, staving off human need for instant gratification (Coren, 2014), and promoting more environmentally friendly behaviors (Barton and Pretty, 2010).

Despite the multiple benefits that nature can have on recovery from surgery and human behavior, how much exposure to nature and what kind of exposure do we need to optimal mental and physical health? That question is a complex one with many components. Researchers at the University of Essex, Jo Barton and Jules Pretty, conducted a study to assess one component of exposure to nature and health. Their multi-study analysis assessed the amount of green exercise (physical activity conducted in the presence of nature) needed to improve two indicators of mental health: self-esteem and mood (Barton and Pretty, 2010).

When defining mental health, it is important to note that it is not merely the absence of disease or disability, but is a “balance between self-satisfaction, independence, capability, and competency, achieving potential, and coping well with stress and adversity” (Barton and Pretty, 2010). Self-esteem and mood are good determinants of mental health and were measured by the Rosenberg Self-Esteem Scale and the Profile of Mood States (Barton and Pretty, 2010).

Barton and Pretty completed a meta-analysis a sample size of 1252 people from 10 studies conducted in the United Kingdom (Barton and Pretty, 2010). The study looked at the short term benefits of green exercise and had five key findings:

  1. Duration– Positive benefits for mood and self-esteem were seen for even five minutes of green exercise. The benefits continue the longer the duration of green exercise, but there are diminishing returns.
  2. Intensity– The greatest benefit comes from less vigorous exercises.
  3. Qualities of Green Space– All green spaces showed improved self-esteem and mood, but those with water showed greater improvements.
  4. Gender– Results of self-esteem improvements were similar in men and women.
  5. Age– The largest change occurred in those younger with diminishing returns with age (although there are potential confounding factors).
  6. Mental Health Status– Those participants with a poor mental health status before engaging in green exercise showed the greatest change for self-esteem improvements from engaging in green exercise.

The results of this study have many implications for urban planners, architects, medical professionals, and biophilic urbanists alike. Since even the smallest amount of exposure to green space has a positive impact, it is important that green space is accessible to all, but especially to younger and mentally ill populations (Barton and Pretty, 2010).

Physicians should consider adding a prescription of daily exercise in nature for patients grappling with mental illness and diseases related to sedentary lifestyles (Barton and Pretty, 2010). The significance for biophilic cities is that urban nature is needed for respite from urban scenes since it is well established that many populations prefer natural over urban scenes (Ulrich, 1984). Nature is needed, but is especially essential in cities.

To read Barton and Pretty’s complete study, please click here.


Barton, J., & Pretty, J. (2010). What is the Best Dose of Nature and Green Exercise for Improving Mental Health? A Multi-Study Analysis. Environmental Science & Technology, 44(10), 3947-3955.

Coren, M. J. (2014, January 6). A Dose of Nature Helps City Dwellers Fight Their Need for Instant Gratification. Fast Company. Retrieved March 3, 2014, from

Parker-Pope, T. (2008, October 17). A ‘Dose of Nature’ for Attention Problems. New York Times. Retrieved March 3, 2014, from

Ulrich, R. (1984). View Through A Window May Influence Recovery From Surgery. Science, 224(4647), 420-421.