By Cindy Kerson, UC Master Gardener of Napa County
A walk in the park, a pause at a window overlooking your garden, or a day at the beach. We all
know these are rejuvenating moments. But why? What happens in the brain to make them so?
What are the chemical and physiological functions in your brain during these experiences?
Until about 200 years ago, humans lived alongside all other creatures – outside. We went indoors
for sleep. We foraged, hunted, cooked, worked and played outdoors.
Our brains are wired for this connection with nature. Being indoors is evolutionarily meant for
protection from dangers such as sabretooth tigers, enemies and weather.
This innate desire for the outdoors is known as biophilia, meaning that we are wired to feel
affinity with nature and are attuned to its rhythms. So, the next time you feel like disconnecting,
think instead that you are in turn connecting – with nature.
Our brains produce a chemical known as brain-derived neurotropic factor, or BDNF. This
signaling molecule, sometimes called neuron’s fertilizer, serves an important function in the
hippocampus, the area of the brain responsible for learning and memory. When we exercise, this
chemical is stimulated, which in turn stimulates learning and memory.
Exercising outdoors, as opposed to inside your home or at a gym, provides a double whammy.
The areas of our brain that respond to nature are stimulated, which creates a sense of being at
peace with our surroundings, while the exercise increases BDNF levels.
Both the human brain and the soil are composted of intricate networks. Our brain relies on many
parts to complete a single task. Neurons and many other cells use pathways to send messages to
and fro. In the soil, protozoa, fungi, bacteria and other living beings provide a network between
plants. They grow and contract to transport nutrients, water and information from plants that
don’t need them to those that do.
Some studies suggest that living in a green environment is better for the brain. The Green Heart
Project reported improvement in the cognitive skills of young people after they planted
thousands of trees in their neighborhoods. Young people in neighborhoods with few trees did not
show the same cognitive improvement.
One Finnish study suggests that we may be too clean. If we don’t expose ourselves to nature
enough, we don’t benefit from its healing properties. One such natural healer is Mycobacterium
vaccae, a soil-derived bacterium known to stimulate production of serotonin. This
neurotransmitter, found in the gut and the brain, is responsible for feelings of satiety and well-
being. It also contributes to a healthy immune system.
Don’t stop at green, though. Why are we drawn to moving water, like ocean waves and
waterfalls? So we can pick up negative ions, of course. The air around moving water is highly
charged with negative ions, considered nature’s air filter. When we inhale them, they positively
influence neurotransmitters, boost cell metabolism, improve immune performance and trigger
beneficial biochemical processes within the body.
As you consider the hours you need to spend in the garden this weekend, don’t worry; you won’t
overdo it. The brain also has a natural inhibitor called galanin that will modulate all that BDNF
you produced.
There’s no limit to what being in nature, and especially moving in nature, can do for you. And
your thoughtful influence on nature, by using integrated pest management practices, is what you
can do for it in exchange.