Anyone living in the Sonoran Desert during the summer monsoon knows the sweet smell of the land suddenly coming alive. It’s an intoxicating combination of scents — a kind of olfactory fireworks show, with one plant after another releasing its unique, celebratory aroma in response to long-awaited moisture.
Gary Paul Nabhan (pictured) — a contemplative ecologist, desert writer and garden designer — famously summed up this phenomenon with the title of his 1982 book, The Desert Smells Like Rain. The book became a classic for its Sonoran Desert natural history and intimate portrayal of the Tohono O’odham people, and Nabhan went on to write or edit three dozen other works about the links between biodiversity and cultural diversity, and between food and faith.
Four decades later, Nabhan is coming back to where his career began and answering a question he long has wondered: Why, exactly, does the desert smell like rain?
Over the past few years, Nabhan and his colleagues have investigated what causes Sonoran Desert plants to release pungent fragrances just before or during summer monsoon storms in the desert. They’ve also discovered that breathing in these aromas offers health benefits to humans.
According to Nabhan’s recently published research, volatile oils released by Sonoran Desert plants can help improve sleep, stabilize emotions, enhance digestion and heighten mental clarity. The fragrant essential oils emitted by the plants — technically called “biogenic volatile organic compounds” — are easily absorbed by the human body through skin contact and inhalation. Within two minutes after breathing in the beauty, aromatic compounds were found to be present in the bloodstream. Within 30 minutes, the beneficial substances were detectable in the body’s organs.
Some aromas from flowering plants are designed to attract pollinators, but Nabhan says other fragrant oils likely exist to protect plants from UV radiation, heat and browsing animals, as well as to help leaves retain moisture. The oils build up on the plants for months and are released into the atmosphere as barometric pressure and wind speed change and moisture fills the air. “Our studies show that the chemicals reducing stress in the plants also reduce stress in humans who regularly inhale those fragrances,” Nabhan says.
While anyone can imbibe in this stress detox by simply hiking on a rain-soaked trail, Nabhan is designing public fragrance gardens to help people get the most out of the desert’s medicine cabinet. The first of these, the Desert Smells Like Rain Garden, is at the Sonoran Desert Inn and Conference Center in Ajo. A strategic collection of plants fills a large courtyard at the inn, and visitors and guests can take an aromatic stroll while stopping to read interpretive signs. Nabhan now is collaborating on a stress-reducing fragrance garden at the student health center on the University of Arizona campus in Tucson, where he was a faculty member for the College of Social and Behavioral Sciences before retiring in December.
“When it rains, the smells are intoxicating and unlike anything I have ever experienced,” says Sonoran Desert Inn manager J. Brady, a native of the Midwest. “The fragrance garden is a way for our guests to unplug.”
Nabhan became interested in investigating desert aromas after he attended a workshop on the Japanese practice of shinrin-yoku, or “forest bathing,” which encourages inhaling the scents of trees. He wondered if the aromatic chemical compounds in Asian coniferous forests, widely studied for their health benefits, could also be found closer to home, in the Sonoran Desert.
Nabhan and his colleagues surveyed some 178 native plants in Sonoran Desert and Organ Pipe Cactus national monuments in their search for smells. Of these, they found more than 60 species emitting fragrant oils with known therapeutic effects, including 15 compounds that dominate Asian forests and provide proven health benefits. The aromatic powerhouse plants include creosote, wild oregano, brittlebush, bursage, canyon ragweed and desert lavender.
Nabhan says scientists researching fragrances may have overlooked the Sonoran Desert because of their focus on temperate forests. But he points out that the demanding conditions in most deserts encourage plants to accumulate large amounts of beneficial volatile oils, making the desert a prime location for aromatherapy. He points to the recent phenomenon of “cactus forest bathing” workshops, popping up around Tucson, that teach desert dwellers how to soak in the healing smells just outside their doorsteps.
While it may be tempting to buy essential oils and put them in a home diffuser to try to get the same effects, Nabhan says there’s no way to replicate the aromatic symphony that nature provides. Each plant’s fragrant oils have benefits on their own, but the combination of fragrances packs the biggest punch. And while the music may be loudest during the monsoon, the essential oils are playing to different seasonal harmonies throughout spring, summer and fall. “It’s an olfactory concert,” Nabhan says. “I call it an ‘osmocosm,’ or world of smell.”
When Nabhan was in the early days of his career 40 years ago, he says, ecology was viewed from a subject/object perspective, where the plants were the passive subject of a scientist’s inquiry. Now, he sees his research as an ongoing dialogue, with every smell containing a message. “Plants are active communicators,” he says. “There is a whole lexicon of desert fragrances by which the plants are communicating with other plants, animals and humans.”
Nabhan is planning to create more fragrance gardens in public spaces and continue studying the “interspecific language” of desert fragrances. His first book was re-released in August as a special 40th anniversary edition. In a new preface, Nabhan thanks the 8-year-old Tohono O’odham boy who first told him, “The desert smells like rain.” That kind of non-technical yet spot-on description was underappreciated, except by pollination ecologists, until the 1990s, he says.
“As desert dwellers, we have fragrances speaking to us all the time,” Nabhan says. “We need to crack the code on what they are saying.”