Americans have become indoor animals. On average, we spend about 90 percent of our time inside buildings and cars. When we venture outside, we’re often so glued to our smartphones that we’re oblivious to the natural world.

That’s probably not a good thing. Growing evidence suggests that interacting with nature makes people happier and healthier. Surgical patients go home sooner if their hospital rooms have a view outside, for example. A walk in the park can boost the concentration of children with attention deficit hyperactivity disorder. And spending time in a forest has been shown to lower stress levels and blood pressure while boosting immune function.

For those of us disinclined to spend time outdoors — or unable to because we work long hours in hermetically sealed offices — an emerging architectural movement called biophilic design aims to incorporate a bit of nature into our buildings. Perhaps ironically, the trend has been embraced by some of the same tech giants whose products have helped fuel our nature-shunning addiction to technology.

In downtown Seattle, Amazon's new office features three glass-and-steel domes, dubbed the Spheres, that cover a cloud forest of more than 40,000 plants. Twenty-five minutes to the east, treehouses have sprouted on Microsoft’s suburban Redmond, Wash., campus. A nine-acre rooftop park adorns Facebook’s Menlo Park, Calif., headquarters, not far from Apple’s new spaceship-like building in Cupertino that surrounds a 30-acre park, orchard, and pond.

More than 40,000 plants, most from cloud forest ecosystems, live within Amazon's Spheres in Seattle. Jordan Stead / Amazon

“The first step is, ‘Why don’t we just go outside? The second step is, ‘We’ll just bring some trees inside,’” said Amanda Sturgeon, a biophilic design expert and CEO of the International Living Future Institute, a Seattle-based nonprofit that encourages sustainable practices. “We’re trying to go to the place after that — which is, ‘What could we learn from what makes us love being outside and incorporate it into the design of our buildings?’”

In 2016, Sturgeon and like-minded architects, builders, and researchers banded together to form the Biophilic Design Initiative to help move the fledgling movement into the mainstream. She and other green building experts welcome the tech companies’ new office spaces as high-profile examples of nature-friendly design and evidence that employers may be doing a better job of prioritizing employees’ well-being.

Office buildings as test beds

With tens of thousands of employees between them, the companies’ new workspaces could also serve as test beds for biophilic strategies — helping them find their way not only into office buildings but also into schools, homes, and other indoor spaces.

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Cities themselves may be catching the biophilia bug, Richard Louv, author of "Last Child in the Woods" and an expert on the relationship between nature and health, told NBC News MACH in an email. A nonprofit group called Biophilic Cities is trying to expand urban connections to nature, for example, while some cities are erecting environmentally friendly “plyscrapers” made mostly of wood.

Large windows maximize daylight and views at Seattle's Bullitt Center, which houses the International Living Future Institute and other office spaces. Benjamin Benschneider / Bullitt Center

Microsoft has cited the science of biophilia and employees’ desire to work outside more as key factors in its decision to build treehouse meeting spaces and parklike “outdoor districts.” In an email to MACH, Ben Eiben, Amazon’s horticulture program manager, likewise pointed to the health benefits of green spaces as an impetus for the company’s building project.

“The Spheres are a result of innovative thinking about the character of a workplace and an extended conversation about what is typically missing from an urban office — a direct link to nature,” he said. The space was created, in part, to help employees “innovate, create, or simply recharge while being immersed in space that’s more like a forest in the clouds than an office,” he added.

Experimenting with new designs

Bill Browning, a partner at the New York City-based environmental consulting firm Terrapin Bright Green, said research has helped advance biophilic design by showing how different features support different psychological or physiological outcomes. He helped develop what he calls 14 patterns of biophilic design — each supported by documented benefits related to stress, cognitive performance, and mood.

Breezes created by ventilation systems can keep people alert, for example. And paths meandering through building interiors or adjacent gardens can encourage curiosity among workers, he said, while water features help lower stress and blood pressure.

Employees sit on cocoon-like chairs at Etsy's office in Brooklyn Emily Andrews / Etsy

Google is an acknowledged leader in experimenting with biophilic design to boost employee productivity and satisfaction. Browning, whose consulting firm has worked on the tech giant’s building portfolio, declined to detail specific Google projects. But he said he was helping the company develop science-based metrics that it will eventually apply to its buildings and campuses worldwide.

In its workspaces in Austin, Texas, Pittsburgh, and elsewhere, Google has measured the amount of natural light its employees receive and tested biophilic elements ranging from plants, terraces, and water features to organic patterns in carpeting. In Google’s Chicago office, employees can access sunshine-simulating full-spectrum light by adjusting the color temperature of task lights. Studies link sunlight to elevated mood and reduced stress, among other benefits.

Meanwhile, Amazon’s Spheres automatically adjust the level of artificial light to supplement natural light as needed throughout the day. Other designers are developing lights that mimic the shifting color and intensity of daylight — from the brilliant white of the noonday sun to the warmer hues of sunrise and sunset — to match our circadian rhythms.

Preliminary studies suggest that such circadian lighting systems boost employees’ alertness, productivity, and sleep patterns.

Real and simulated nature

Expansive green roofs and walls are popping up in many new biophilic office buildings as well. Amazon’s Spheres, for example, feature “living walls” adorned with 200 plant species, including one that rises 60 feet.

In 2017, Santa Cruz, Calif.-based Plantronics unveiled its “Habitat Soundscaping” technology that uses the sounds of water and natural scenes projected onto walls or ceilings to provide relief from noisy or distracting workplaces. The biophilic system can be designed to kick in automatically when open office spaces become too loud.

“Most of our brain processing is focused on sight, but if we can experience something with more than one sense, then the impact is definitely stronger,” Browning said. Even sounds, smells, and textures inspired by nature can enhance wellbeing, though not quite as much as the real thing.

Louv praised the tech companies’ efforts to aid their workers through better buildings but cautioned that they’re only a start. “The challenge,” he said, “will be to make sure biophilic design isn’t just something for elite technologists living in green bubbles.”

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