Way back in 1956, the Leningrad biologist Professor Boris Tokin demonstrated that conifers did a good job disinfecting their surroundings. He discovered that the air around stands of young pines was almost germ-free. The cause of this clean air was the trees themselves, which were giving off phytoncides, a kind of plant antibiotic.

Why do conifers to this? The answer is that they are constantly being attacked by an enemy we cannot see, one that drifts in the breeze. Every 35 cubic feet(1 cubic meter) of air carries up to ten thousand fungal spores just waiting for chance to land on a broken branch or damaged bark. From there, the fungus grows into the tree and slowly eats it from the inside out. The wood rots and tree dies. It’s understandable that many conifers want to defend themselves at the earliest possible opportunity, preferring to take out the attackers before they even land.

Conifers fight fungal spores before they reach their bark, and people who suffer from allergies benefit from the trees’ preventative measures. But people who suffer from allergies are not the only beneficiaries. Unbeknownst to you, you breathe in the trees’ defensive compounds, the phytoncides, with every breath you take, and they help protect your body, too. In your case, they trigger a reaction that reduces inflammation. In addition, phytoncides have been found to reduce the activity of cancer cells. Japanese researchers at the Nippon Medical School discovered this when they sent test subjects out into the forest or the city. Cancer killing cells and anti-cancer proteins increased in those people who visited the forest but no in those who visited the city, and the elevated concentrations of both could be detected in the participants’ blood up to seven days after the forest walk.

Excerpt from “The Heartbeat of Trees”