We all know that being in nature is good for our health and mental well-being. But how does it work its magic? It is this puzzle that led botanist Kathy Willis on a recent mission. The former director of science at the Royal Botanic Gardens, Kew, in London and current professor of biodiversity at St Edmund Hall, University of Oxford, says that what she discovered has changed her life. In her book Good Nature, she explores the growing body of research revealing what happens in our brains and bodies when we interact with nature. She tells Kate Douglas that, while there is a lot more to discover, we have already learned plenty that can improve our lives.
Kate Douglas: What happens when we look at nature?
Kathy Willis: It induces different pathways in our bodies. Our heart rate and blood pressure fall, stress hormones like adrenalin decrease and our brainwave activity is heightened in areas showing we are calmer and more clear-minded.
Are there certain “natural” colours we should seek out?
When you look at these physiological markers of calmness, it’s green-and-white leaves and yellow or white flowers that have the most pronounced effect. But a Czech study of more than 2000 people found that they preferred to look at radially symmetrical flowers and flowers that were blue. We don’t know what effect their shape has on our physiology, but that study shows that our preferences don’t always tell us what’s best for us in terms of physical or mental well-being.
What is the best kind of landscape to view?
It is an open one with a few scattered trees. This makes us physiologically and psychologically calmer, and there are two reasons for this. First, it detracts from your focused attention: it’s more of a general background attention, so it gives you a sort of mental mini-break.
Second, when we look at something, our eyes pick up the complexity of the scene. We call this its fractal dimension, which is a measure of complexity that indicates the degree to which objects fill the available space. We prefer landscapes with mid fractal complexity. This is equivalent to a more open kind of landscape with a few trees.
These landscapes result in a particular brainwave response – heightened alpha and beta frequencies and reduced delta frequencies – which studies have shown are associated with increased focus and a feeling of calm.
You argue that smelling nature is even more beneficial than seeing it. Why?
Smell was a completely unknown sense to me. I mean, flowers smell nice, but I didn’t think about it. I didn’t realise that when you breathe in a plant scent, it passes across your lung membrane and some of those molecules pass into your blood. Many scents are now being shown to affect biochemical pathways in the same way as a prescription drug. And they can have long-lasting effects.
Which smells have known health benefits?
Lavender calms you down: it contains a volatile chemical called linalool, which has anti-anxiety effects. Then there’s pinene, the predominant piney smell you get in a pine forest, which also reduces stress.
Another interesting one is plants in the cypress family, like cedar and juniper, which contain compounds called sesquiterpenoids. People who breathe those in have increased activity in the parasympathetic nervous system, indicating relaxation, but also reduced adrenalin and elevated natural killer cells – the immune cells that attack cancers and viruses. Limonene is another example: it’s found in lots of citrus fruits and is an important anti-inflammatory molecule.
What about natural sounds? Are they good for us too?
Sounds have been shown to calm us. And there’s a big meta-analysis which found that particular sounds are good for certain things. Birdsong, for example, is best at reducing physiological symptoms of stress, whereas water sounds improve mood and cognitive performance. But there are bad sounds, too: the harsh squawking of a crow or a parrot, that does not relax us.
When it comes to spending time in nature, what’s the best medicine – and what dose should we aim for?
To maximise the benefits, you need to spend at least 20 minutes at a time in nature, and at least 120 minutes each week. If you’re going out walking, walk in the park rather than on the streets. There’s a huge difference to what it does for you. The second thing is to seek out areas that will stack the benefits of nature. Go to a copse where you can hear the birds – one that is as far away as possible from the road and its unhealthy sounds. Go where you can smell the air, where there are scented plants like lavender and rosemary. Now, I always choose conifers if I can because pine smells are so good for you – but I avoid dense tree cover because there is evidence that can stress you out.
What about gardening?
Gardening has huge benefits because you’re combining so many of your senses: sight, sound, smell and, by touching the soil, you’re getting that environmental microbiome into your body. But there are some surprising studies. First, you get greater benefits from putting pretty flowers in pots in your front garden than in the back. I think that’s because you’re walking through it all the time. So, concreting over your front garden is probably the worst thing you can do. Also, research has shown that people report greater calming and other health benefits from gardening in an allotment than in their private garden. It might have something to do with community cohesion, but also, with an allotment, you’re planting a whole variety of shapes, sizes and colours and it goes on all year round.
How should we change our homes and offices to make the most of these findings?
In my home office, I’ve got a bottle of hinoki oil [from a species of cypress tree] that I diffuse every couple of days because it increases natural killer cells. I have a green-and-white spider plant. In fact, I have plants all around me now. That’s sight and smell. We can do sound too, with recordings of nature, and touch by increasing the amount of natural, untreated wood around us. We can also take mental mini-breaks: look out of the window onto greenery.
Do we need to rethink urban green spaces?
Absolutely! The implications are huge. We need to build more houses and that is putting big pressure on urban green spaces. People often think that it’s OK for a developer who destroys biodiversity to create it elsewhere. But we absolutely need to have biodiversity around us in cities. You can’t move it somewhere else and hope it’s going to give the same benefits. More biodiversity in cities is good for nature – but it’s critical for our well-being.
This was an abridged excerpt from the article How the healing powers of botany can reduce anxiety and boost health – click here to read the full interview.
