The Green Prescription

Most of us know the feeling. After a walk among trees, by the sea or across open hills, the mind is quieter, the shoulders lower and the breath deeper. For most of human history, nature was simply where we lived. Now, for many of us, it is somewhere we visit. Research is now showing what that feeling of coming home to nature is doing inside the body.

Forest bathing

In the 1980s, Japan's forestry agency introduced a practice called shinrin-yoku, meaning "taking in the forest atmosphere", or forest bathing. It isn't hiking or exercise. It means spending slow, unhurried time among trees, taking in the forest through all the senses: the scent of pine, the sound of leaves, the feel of bark, the dappled light.

Japanese researchers then set out to measure its effects. In studies across 24 forests, people who spent time in the woods had lower levels of the stress hormone cortisol, a lower pulse and blood pressure, and more activity in the calming, "rest and digest" side of the nervous system, compared with time spent in a city.¹ Since then, forest bathing has spread around the world, and reviews of the research generally support its calming effects, though many studies are small.² (See The Cortisol Clock.)

Nature was simply where we lived. Now, for many of us, it is somewhere we visit.

What nature does for health

A large review of more than 140 studies found that people who live with more green space nearby have lower cortisol, heart rate and blood pressure, and lower rates of type 2 diabetes, heart disease and early death.³ Other research points to benefits for mood, focus and recovery.

• Mood. In a Stanford study, people who walked for 90 minutes in nature dwelt less on negative thoughts afterwards, and showed calmer activity in a part of the brain linked with depression, compared with those who walked beside a busy road.⁴
• Attention. Natural settings gently hold our attention without demanding it, allowing the focused, tired mind to rest and recover. Psychologists call this "attention restoration".⁵
• Healing. In a classic study from 1984, patients recovering from surgery in rooms with a window view of trees went home sooner and needed fewer strong painkillers than those whose window faced a brick wall.⁶

Why nature heals: four pathways

The scent of the trees

Trees release aromatic compounds called phytoncides to protect themselves against insects and disease. They give pine and cedar woods their fresh, resinous smell. Professor Qing Li of Nippon Medical School in Tokyo found that after a weekend in the forest, people's natural killer cells, immune cells that seek out viruses and abnormal cells, became more active, and the effect lasted for days.⁸ Breathing in the vapour of tree oils in a hotel room had a similar, smaller effect.⁹ (For more on how plants communicate and protect themselves, read The Inner Life of Plants.)

The sounds of nature

Birdsong, running water and the rustle of leaves seem to help the nervous system settle. In one study, people recovered from a stressful task more quickly while listening to nature sounds than to traffic noise.¹⁰ (See The Sound of Stillness.)

The patterns of nature

Ferns, branches, clouds and coastlines are made of fractals: patterns that repeat at smaller and smaller scales. Research suggests that looking at natural fractals can lower stress, perhaps because our eyes and brains evolved to take them in with ease.¹¹

The microbes of the earth

Soil, plants and fresh air are full of friendly microbes, and contact with them helps train a balanced immune system. In a Finnish study, when the gravel yards of day-care centres were covered with forest floor, turf and plants, the children's skin and gut microbes became more varied within a month, and their immune systems showed signs of better regulation.¹² One soil bacterium, Mycobacterium vaccae, has even been found to activate serotonin-producing nerve cells in the brain in animal studies.¹³ Gardening may be good for the mind in more ways than one. (See The Master Regulator for more on the microbiome.)

How to forest bathe

1. Leave your goals behind. Put your phone on silent, and forget about distance, speed or reaching a destination.
2. Slow right down. Walk slowly, pause often, and let your body lead you.
3. Open your senses. Notice five things you can see, the sounds near and far, the scent of the air, the texture of bark or leaves under your fingers.
4. Breathe deeply. Take slow breaths in through the nose, and enjoy the forest air. (See The Healing Breath.)
5. Find a sit spot. Sit quietly for ten minutes or more, and watch what moves around you.

Two hours is ideal, but even 20 minutes helps. And there's no need for a great forest: a local park, a riverbank, a churchyard or a garden can work too.

Bringing nature into everyday life

• Aim for two hours a week in green or blue spaces, by trees, rivers, lakes or the sea.
• Garden or grow something, even herbs on a windowsill. Get your hands in the soil.
• Walk barefoot on grass or sand when you can. (See Wired and Tired for more on grounding.)
• Bring nature indoors with houseplants, natural materials, and a desk with a view of trees or sky.
• Eat outside, and take phone calls on the move outdoors.
• Follow the seasons: notice the first buds, the changing leaves and the light. (See Living by the Sun.)
• Share it. Walking with friends adds the benefits of connection. (See Social Resonance.)

In the UK, some GP practices now offer green social prescribing, linking people with walking groups, community gardens and conservation volunteering.

At Rootwise, we believe we are part of nature, not separate from it. The same plants that give us our herbal medicines also heal us simply by being near them. Sometimes the best prescription is an afternoon among the trees.