05/05/2026
[walkable futures]
TREES REDUCE CORTISOL FASTER THAN TRAFFIC ENFORCEMENT EVER WILL
Cortisol is a major stress marker caused by the brain perceiving a threat due to the uncertainty of an overload of information. Common scenarios in urban settings can trigger the brain in this manner. These include noise, dangerous (fast-moving) traffic, heat, anxiety from large crowded areas, and the need to keep a constant lookout. Street design itself creates a stress response in a person, and while traffic enforcement can help direct street behavior, it does not help reduce the stress response traffic itself creates.
Research from disciplines of psychology, neuroscience, and public health show that as little as a couple of minutes of exposure to trees and natural environments can reduce levels of cortisol, which is the primary stress marker, as well as reduce the heart rate and blood pressure. Even walking alongside a street lined by trees or viewing trees from a sidewalk can help to calm the body and reduce the stress response.
These effects can be replicated in training evidence-based design interventions.
Research of streets with and without trees show those with trees tend to have lower stress levels, improved and increased happiness, and increased focus, even with the same amount of traffic. Relaxing natural patterns decrease the brain’s need to work and reduce the cognitive as well.
More importantly, from a care-centered focus, while traffic enforcement is a response, trees are a preventive measure. A police presence may help to stop violations, but a tree reduces noise, heat, and the need for the brain to process the environment, which is also a response to stress.
In the real world, there is a clear answer.
To create safer and calmer streets, the optimal solutions extend beyond rules and regulations; they also involve creating the conditions that eliminate stress in the environment. The planting and preservation of trees in our urban environment should be seen as a way to engage in a low‑cost, evidence‑based public health strategy, rather than viewing it merely as a way to improve the aesthetics of our streets.
Care‑centric cities focus on making conscious designs and policies that account for the human condition, rather than depending on regulations to adjust for a threatening urban design.
They create streets that support the recovery of the human nervous system through low key, endless solutions that serve everyone.
Sources:
https://pubmed.ncbi.nlm.nih.gov/33801917/
https://pmc.ncbi.nlm.nih.gov/articles/PMC3799530/
https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2019.00376/full