The path was a rogue one, steep and jagged, with plenty of tree roots to trip over. Leaving her car on the road above, Florence Williams tackled it easily — she traverses it regularly to get from the Palisades down to the C&O Canal. But she didn’t like the message it sent.

“This is typical of finding nature in D.C.,” she said, as Hailey, her lab-husky mix, strained at her leash. “Sometimes access is sketchy. The neighborhood created this trail,” thousands of footsteps wearing a path through the forest — but Williams noted that some grooming and well-placed steps could make it accessible to people with physical limitations, or those wishing to bring a bike down to the towpath. “I wish the city would take on some of these access trails.”

If that sounds like a lot to wish for, consider that Williams has explored the convergence of urban and natural space at its apex. For her new book, “The Nature Fix,” she traveled around the world, from Japan to Scotland to Sweden, observing how different societies incorporate nature into their health and well-being. She discovered a universal desire to connect with nature and found that, often, there are dire results for those who do not.

Study after study shows the beneficial effects of spending time in nature: People who reside near green areas live longer, healthier lives than people who don’t, even when adjusting for income. Walking in nature has been shown to have more benefits than taking the same walk in a city. People living under a flight path are at a higher risk for stress and disease. Children who regularly spend time in nature have fewer behavioral disorders than those who don’t.

This is not good news, because the trajectory of human life has been moving inexorably away from “the round ocean and the living air” extolled by Wordsworth. In 2008, for the first time, more people in the world lived in cities than in rural areas, Williams writes. Traffic on U.S. roads tripled between 1970 and 2007, the number of passenger flights has increased 25 percent in the past 15 years and 83 percent of land in the lower 48 states is close enough to a road that you can hear it.

Still, nearly everywhere, some modicum of nature can be found. And if you’re willing to put up with sketchy trails and the roar of jet planes, the Washington area abounds with it.

Williams, who has two teenagers, moved from Boulder, Colo., to the District five years ago for her husband’s work, and it took some getting used to. Crossing the black truss bridge over Canal Road as cars whooshed by underneath, she noted that along with noise they were probably emitting less-than-salutary compounds, and added that the 800 flights a day zooming by overhead didn’t help.

But it didn’t matter. Nature is nature. And D.C., she has learned, is well-stocked.

“Oscar Wilde has this great quote — that nature is ‘a place where birds fly around uncooked’ — and I think that is true,” she said. “We can find elements of nature in our back yards, we can even find them in houseplants — though I feel like I need a stronger fix than houseplants.”

Down on the canal, a pair of nesting mallards floated serenely, the lush foliage reflecting off the water and bathing them in greenish light. In the winter, when it gets cold enough, Williams and her neighbors gather here to skate down the canal.

“I have a couple of friends who I’ve introduced to near-daily walking, and they’ve stopped taking their meds for mild depression,” she said, adding that exposure to nature has been shown to deactivate an area of the frontal cortex that is responsible for ruminative depressive thinking, or going over and over the same upsetting thing in one’s head.

It does so, she said, because it takes you out of yourself. “You’ll say, ‘There’s a butterfly; there’s an incredible cloud formation; there’s a heron sitting on a rock … and it just makes you feel like you’re part of a larger, more beautiful universe — instead of your disaster of a life.”

Williams didn’t grow up in some pastoral idyll; she was raised in New York City. But she had Central Park as her back yard, and each summer she and her father would drive out west and live out of a van for weeks at a time.

Being in nature is crucial for children, she says. “It gives them a connection they’ll have their entire lives; if they want to seek comfort they’ll know where to go. … They are built to explore, and yet we contain them in these classrooms from a very early age. We say, ‘Here’s a paper, here’s a crayon.’ I kind of shudder to think what we’re doing to their drive for exploration. Right now we’re experiencing this epidemic disconnect from nature. … There are Girl Scout leaders today who don’t take their Girl Scouts camping because they’re not comfortable with it.”

Countries such as Finland incorporate much more outdoor play into the school day than the United States, where in recent decades recess time has dwindled. There are small movements in the United States that give Williams hope, including the advent of “nature kindergartens” similar to those in Western Europe, or Oregon’s week-long outdoor school, a camp-like experience that teaches children about soil, water and plants.

Standing at Fletcher’s Cove Boathouse, where low water had left a landscape of mud and swamp grass, Williams pointed out a great blue heron circling over the Potomac. On a recent day she witnessed the shad migrating up the river to spawn. “It was a true moment of awe. You could actually see hundreds and hundreds of fish, and everyone was watching them — the vultures, the herons, my dog — and of course the humans.”

As a writer, Williams gets many of her ideas when she is walking in nature, and she is not the only one. Albert Einstein, Nikola Tesla and Charles Darwin walked outdoors to stimulate their mental processes.

On a more personal note, she has recently turned to nature for solace: She and her longtime husband are going through a separation, and her walks have helped her through a painful time. “Nature can be really powerful as metaphor, especially during grief. It reminds us we can adapt and change and grow again. So I find myself putting into practice more lessons from the book than I expected.”