Vertical gardens set up on the exterior of buildings can reduce some of the stress levels caused by living in big cities, according to a new study. Researchers used virtual reality in over 100 people and found the vertical greenery has a stress-buffering effect.

Rapid urbanization has been associated with decreased nature exposure and increased environmental stressors like traffic noise and pollution. Considering that nature can combat stress and promote wellbeing, there have been tremendous interests and collective efforts across the globe to increase green space, with examples ranging from Europe to China. 

Vertical greenery refers to the integration of vegetation onto the vertical structures of buildings, which differs from green roofs that utilize the flat horizontal space atop buildings. In the past, vertical greenery mainly consisted of self-climbing plants like vines that spread over buildings’ facades. But now the concept has been expanded much further. 

Gardens take to the skies

Implementing vertical gardens can increase greenspace above-ground, thereby overcoming land constraints common in high-density urban areas, and provide important ecosystem services – such as cooling system, sound absorption which decreases noise pollution, and absorption of harmful pollutants which mitigates air pollution. But the advantages of vertical gardens may be even greater, especially on our mental health.

Existing research on nature’s effects on emotion and stress has been dominated by natural environments such as parks and forests. No experimental study has been done to examine the physiological benefits of having a row of buildings covered in vertical greenery. Now, researchers at Nanyang Technological University, Singapore hoped to address this gap with a new study.

They asked 111 participants to walk down a virtual street for five minutes, using VR headsets. Participants were randomly assigned to a street that had rows of planted greenery on balconies, walls and pillars or buildings, or on one with only buildings that had green painted walls instead of green plants. Traffic noise was played out during the experiment.

Those who viewed buildings with only a green pain had a significant increase in stress, as recorded by one measure of heart rate variability. Meanwhile, those who saw the buildings with the green plants didn’t experience any change in stress. This is in line with previous studies that have found nature to have beneficial effects on stress and emotion. 

Participants then replied to a questionnaire to assess their positive and negative emotions and the level of anxiety they were feeling. They said to feel less positive when walking through the street with buildings covered by only green walls. Meanwhile, those walking through the street with buildings covered by plants didn’t report feeling either more or less positive

“With urbanization, more people are expected to be living in urban areas globally in future. It is thus important for urban city planners and architects to understand factors that can contribute to healthy living, as urban planning can have a direct impact on quality of life for the population. Our work can guide efforts to green cities, by providing evidence of how vertical greenery can be a viable way to integrate nature into our built environment and promote mental health,” Lin Qui, co-author, said in a statement.

The study was published in the journal Landscape and Urban Planning.