Studies show that the oils and other chemicals released by plants after a rainstorm may explain the feelings of euphoria and health benefits that result from a desert hurricane.

“The Sonoran desert flora is one of the richest plants in the world producing fragrant volatile oils, and many of these scents benefit the health of humans, wildlife, and the plants themselves by reducing stress,” says Gary Nabhan, researcher. a scientist at the University of Arizona Southwest Center and Chair of the Southwest Frontier Food and Water Security Department.

Nabhan is the lead author of two new studies, one in International Journal of Environmental Research and Public Health and the other in desert plants— which explain how volatile organic compounds that have evolved to protect plants from harmful solar radiation, heatwaves, drought stress and predatory animals can also be beneficial to human health.

Monsoon season in the desert

Nabhan was inspired to explore the health benefits of desert scents after learning about “forest bathing,” an ancient practice originating in the coniferous forests of East Asia that involves spending time in nature to reduce stress and improve overall well-being.

At first, he was frustrated by the fact that the forests closest to him are thousands of feet high in the Catalina Mountains, which culminate in about an hour and a half from downtown Tucson.

“But then I thought that some of these compounds are found in desert plants,” says Nabhan, “and we know that at certain times of the year we have amazing aromas, especially right after a thunderstorm during the rainy season.”

The southwest monsoon season usually runs from June 15 to September 30. About half of the region’s average annual precipitation falls during these three and a half months.

Nabhan and his collaborators, Eric Dougherty, a former Southwest Center intern, and Tammy Hartung, co-owner of Desert Canyon Farm in Canyon City, Colorado, identified 115 volatile organic compounds in 60 Sonoran Desert plant species. released just before, during and after rain. Of these, 15 have been shown to provide tangible health benefits in past studies.

“The fragrant volatile organic compounds of desert plants can go a long way towards improving sleep, stabilizing emotional hormones, improving digestion, increasing mental clarity, and reducing depression or anxiety,” says Nabhan.

“Their accumulation in the atmosphere directly above the desert vegetation is responsible for the smell of rain reported by many people. It also reduces exposure to harmful solar radiation in a way that protects the desert plants themselves, the wildlife that use them for food and shelter, and the people who live among them.”

According to Nabhan, many desert plants produce more volatile oils in summer to protect themselves from harsh conditions.

“The production of oily compounds occurs during times of severe drought and extreme heat, but they remain on the leaves until the summer rains arrive.

“We used to think that during the summer rains, these oily and sticky substances were washed away and released into the air, but now there is some evidence that with the humidity and strong winds that we get when it starts to rain, they are released. into the atmosphere before it actually rains, and contribute to that incredible surge of anticipation you feel right before the first raindrop of a thunderstorm. From there, they enter our lungs and bloodstream within minutes.”

Healing gardens?

The creosote bush is one of the most iconic plants of the Sonoran Desert and is often referred to as the plant that gives the desert a familiar scent when it rains. One of the healing compounds that give creosote’s familiar smell is trans-caryophyllene, which actually comes from a fungus living inside the plant, not from the plant itself, according to Nabhan.

Armed with his knowledge of desert plants, Nabhan is part of an initiative to create scent gardens that promote healing and well-being in the Southwest.

In March, Nabhan and colleagues set up one such garden at the Sonoran Desert Inn and Conference Center in Ajo, Arizona. By the end of autumn, they would like to complete another one at the foot of Tumamok Hill, where many people go to exercise outdoors. The hill’s proximity to St. Mary’s Carondelet Hospital makes it even more strategically important, Nabhan says, suggesting that patients and their families reap the benefits of the garden’s health.

“I would like to see these fragrant gardens around every hospital, community clinic and bed and breakfast – wherever a person goes to heal, relax and rejuvenate,” says Nabhan. “These community gardens will not only produce nutritious food, but also offer residents, out-of-towners and tourists the perfect opportunity to experience how the desert smells like rain.”

Source: University of Arizona

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