I went out to the hazel wood,
Because a fire was in my head.
—William Butler Yeats
People feel better out under the trees.
So do most songbirds, owls, butterflies and brook trout. So do our creeks, soil microbes and water tables. Even a parking lot feels better — certainly to humans — under the blessed shade, heat relief and refreshing stir of a tree canopy on a July afternoon.
The whole world, in fact, gets such good vibes from trees that many researchers are recommending that we plant trees as an obvious low-tech solution to many of our world’s most baffling crises.
For one thing, trees generate rain. Through a remarkable transpiration process, their leaves return moisture to the atmosphere. One large oak has the potential to release 40,000 gallons of water per year. Trees also capture and conserve rainfall via their canopy, shade, microbe-rich humus layers and deep roots.
In fact, a forest in one region will often send free shipments of valuable rain far downwind to drier locations.
“The direct relevance of trees and forests for protecting and intensifying the hydrologic cycle … and the sharing of atmospheric moisture with downwind locations is beyond reasonable doubt,” says David Ellison, lead author of a recent study on this tree-rain link.
These findings throw sunlight on the strangely persistent droughts that have dehydrated vast swaths of Africa, Asia, Mexico and South America in recent years. Upwind, deforestation has left dried-up weather patterns in its wake.
The Global Innovation Lab for Climate Finance has thus recommended the restoration of Latin American “cloud forests”—the misty high canopies that once covered the region’s mountains.
As a 2015 study from the European Environmental Agency points out, such forests also store and retain precipitation longer than denuded areas, releasing it through dry periods to thirsty lowlands.
These findings should catch notice in the United States, where drier weather patterns are taking a toll on agriculture, water tables and cities, and where previously protected federal lands have been targeted for aggressive logging.
But since humans rarely “miss the water till the well runs dry,” a number of other tree benefits might stir Americans to find shovels and plug some native saplings into the ground this spring.
Trees induce tranquility. Their beauty, bird chorale music, even the phytoncide vapors they exude, all induce feel-good brain chemicals in humans.
Tree-lined neighborhoods and housing projects also experience remarkably lower violence rates than those lacking trees. Researchers say that trees appear to inspire trust, goodwill, even euphoria.
To glimpse this yourself, check out photos of the ethereal cherry trees blooming along the Potomac last month in DC— beneath them, human crowds from around the globe, myriad ethnicities and ages, faces lifted with delighted smiles for one another and the trees.
It’s hard, seeing so much goodwill, not to wonder if government leaders around a globe strained with conflict might not resolve things more amicably in meetings held outside under some trees.
Trees benefit not only mental but physical health—increasing the oxygen count, shade and beauty that beckon people outdoors to exercise and meet neighbors and defrag from work. They make for cool places to live. And that cool is measurable.
“On average, it’s seven degrees warmer in New York City than it is just outside the city,” says David Haskell, tree devotee and biology professor at University of the South in Tennessee, “partly because of all these hard surfaces absorbing heat. But trees change the weather in a city. They have a significant cooling effect. They save a lot on air-conditioning.”
Meanwhile, these no-cost solar-powered air conditioners also clean smoggy air, filtering out tons of the particulate matter (e.g., soot) that is particularly deadly to human lungs.
These air freshening benefits led a report from the Nature Conservancy to conclude that urban tree programs could directly save thousands of human lives per year—both local and global.
Tree of Life
How many other species could be spared by re-canopied landscapes is impossible to estimate, but the loss of canopy and woodland habitat has been a leading cause of species extinction around the globe.
One native, mature tree constitutes a vertical, microcosmic world of climate, air, water, soil and myriad beneficial species.
That’s reason enough to plant aplenty, this spring month of Arbor Day, Earth Day, Easter and other occasions to raise the dead.
For tips on planting and tree-care, nursery sources, native species or forest advocacy, visit the websites of the Arbor Day Foundation, the National Wildlife Federation, the Southern Appalachian Forest Coalition or your state’s forestry service.