Wednesday, April 20, 2016

A Computer with a Great Eye is About to Transform Botany

By Margaret Rhodes

My dad is a wildlife biologist, and during road trips we took when I was growing up he spent a lot of time talking about the grasses and trees along the highway. It was a game he played, trying to correctly identify the passing greenery from the driver’s seat of a moving car. As a carsick-prone kid wedged into the back seat of a Ford F150, I found this supremely lame. As an adult—specifically, one who just spoke with a paleobotanist—I now know something about my father’s roadtripping habit: Identifying leaves isn’t easy.

“I’ve looked at tens of thousands of living and fossil leaves,” says that paleobotanist, Peter Wilf of Penn State’s College of Earth and Mineral Sciences. “No one can remember what they all look like. It’s impossible—there’s tens of thousands of vein intersections.” There’s also patterns in vein spacing, different tooth shapes, and a whole host of other features that distinguish one leaf from the next. Unable to commit all these details to memory, botanists rely instead on a manual method of identification developed in the 1800s. That method—called leaf architecture—hasn’t changed much since. It relies on a fat reference book filled with “an unambiguous and standard set of terms for describing leaf form and venation,” and it’s a painstaking process; Wilf says correctly identifying a single leaf’s taxonomy can take two hours.

That’s why, for the past nine years, Wilf has worked with a computational neuroscientist from Brown University to program computer software to do what the human eye cannot: identify families of leaves, in mere milliseconds. The software, which Wilf and his colleagues describe in detail in a recent issue of Proceedings of the National Academy of Sciences, combines computer vision and machine learning algorithms to identify patterns in leaves, linking them to families of leaves they potentially evolved from with 72 percent accuracy. In doing so, Wilf has designed a user-friendly solution to a once-laborious aspect of paleobotany. The program, he says, “is going to really change how we understand plant evolution.”

The project began in 2007, after Wilf read an article in The Economist titled “Easy on the eyes.” It documented the work of Thomas Serre, the neuroscientist from Brown, on image-recognition software. Serre was at MIT at the time and had taught a computer to distinguish photos with animals from photos without animals, with an 82 percent rate of accuracy. That was better than his (human) students, who only only pulled it off 80 percent of the time. “An alarm went off in my head,” says Wilf, who cold-called Serre and asked if this computer program could be taught to recognize patterns in leaves. Serre said yes, and the two scientists cobbled together a preliminary image set of leaves from about five families and started running recognition tests on the computer. They quickly achieved an accuracy rating of 35 percent.

By now, Wilf and Serre have fed the program a database of 7,597 images of leaves that have been chemically bleached and then stained, to make details like vein patterns and toothed edges pop. Small imperfections like bug bites and tears were purposefully included, since those details provide clues to the plant’s origins. Once the software processes these ghost images, it creates a heat map on top of them. Red dots point out the importance of different codebook elements, or tiny images illustrating some of the 50 different leaf characteristics. Together, the red dots highlight areas relevant to the family the leaf may belong to.

This, rather than detecting species, is the broader goal for Wilf. He wants to start feeding the software tens of thousands of images of unidentified, fossilized plants. If you’re trying to identify a fossil, Wilf says, it’s almost always of an extinct species, “so finding the evolutionary family is one of our motivators.” Knowing the leaf’s species isn’t as helpful as knowing where the leaf came from or what living leaves it’s related to—invaluable information to a paleobotanist.

In this way, Wilf and Serre’s tool creates a stronger bridge between the taxonomical aspects of paleobotany and the ecological side of things. Ellen Currano, an assistant professor in the Department of Geology and Geophysics at the University of Wyoming, says that bridge has been sorely lacking. “You could go into a herbarium and look at leaves, or say, ‘I see big leaves, it must be from a wet place,'” but that’s less than efficient.” Currano, who has studied with Wilf in the past but did not work on this study, also points out that modern botanists can often discern a leaf’s taxonomy by looking at the flower or the fruit, but that those often get fossilized separately from each other. “It’s a tremendous challenge to have the leaf, but not flower or fruit,” she says. “So [Wilf’s tool] is an important breakthrough in that it’s taxonomy based on leaves.”

It’s also taxonomy based on machine learning and image recognition. “Everyone”—at least, every paleobotanist—“has had that dream in their head, if only I could just take a picture of this, and get an identity,” Currano says. In seeking to fulfill that wish, Wilf has taken the same approach to studying fossils that Google engineers have taken to streamlining your search results, or teaching a computer to dominate at Go. Wilf even goes so far as to call his tool “an assistant.”

“Assistant” is an apt description. After all, Wilf’s creation doesn’t always provide hard answers (the software, he reiterates, is 72% accurate, not 100%), but it does serve up helpful prompts and ideas. The computer can quickly, and without bias, see what a well-trained botanist might otherwise overlook—and once the computer presents a promising line of inquiry, human analysis can resume. It’s the kind of tool that Wilf is optimistic will unleash “a flood of new botanical information”—but he’s definitely not worried about his job. “It’s not going to replace botanists,” he says, “but it is going to show them where to look.”

Wednesday, March 23, 2016

Leading by the Nose

For humans, walkable neighborhoods and commercial hubs reward strolling with varied architecture, safe street crossings, and a mix of things to do and see on foot. For dogs, there is a much larger world of scent. Can our canine companions guide us to a richer walking experience?

Frank Edgerton Martin

Dogs and other animals understand sidewalks and parks not as visually ordered settings but as shifting islands and drifts of smells. When we humans step out the door, it’s basically the same outdoors we left behind. But for the dog with us on a leash, a street is like a flowing stream filled with the scent trails of passing people and dogs. It’s an ever-changing place.

In 2003, I adopted a yellow Labrador named Samson from the Hennepin County Humane Society. When I first saw him, he struck me as quiet and observant as he sat there upright, regarding the other dogs as they barked and whimpered. For years, Samson spent his days sitting Sphinx-like on the front steps, left paw crossed on right, surveying passersby. He became famous among the neighbors for wanting to sit outside even on the coldest January days.

Samson loved meeting people and other dogs. He was a natural greeter, but we found little social life along the roads and subdivisions of our Lake Minnetonka neighborhood. And because I myself was more interested in architecture than in exercise, I often found our walks boring. But Samson and I both needed exercise and to get outside for strolls. Over the years we developed a set of alternative suburban environments that made sense for both of us.

Instead of walking by lawns and large houses, we got in the car (a thrill for Samson) and drove to denser places where we could do the things we liked, such as: smelling other dogs, visiting antique shops, sniffing sidewalk trees, and sitting in outdoor cafés while greeting people and watching traffic. We often went to downtown Excelsior, a 19th-century town where we could do all of these things. But we also made new discoveries. For some reason, Samson loved outlet malls, perhaps because the long sidewalks afforded him the chance to meet a lot of people.

I took him to Tonkadale Greenhouse and other nurseries where we could walk among the plants in winter, admiring shoppers could pet him, and we could take in the fragrances and humidity. In summer, we went to public docks on Lake Minnetonka, where Samson greeted those departing from the tour boats. Seniors and teenage girls particularly loved him.


In her collection of essays On Looking: Eleven Walks with Expert Eyes, Alexandra Horowitz takes us along on eleven treks, mostly in Manhattan, with experts in a variety of different fields—graphic design, geology, entomology, and so on. Another one of the experts is her dog Flip, who reminds me of a more citified version of Samson.

Horowitz is a cognitive psychologist who writes extensively on dogs and how they perceive the world. In describing her walk with Flip, she notes that “smell, like memory, is entirely personal. It cannot be shared with the ease that an image, rendered in ink or oils, can be experienced by hundreds of millions of viewers.”

Smells are not easily communicated in words; we humans have only vague olfactory classifications such as “sweet,” “earthy,” or “pungent.” But dogs like Flip and Samson experience nuanced smells in thousands of variations. They may not have a word for each, but they have recognition all the same. For dogs, smells form an unfolding map of information about specific places and other animals and people. “Their world has a topography wrought of odors . . . the landscape is brightly colored with aromas,” writes Horowitz.


When touring a neighborhood, we humans use visual classifications such as “late Victorian” or “New Urbanist.” Dogs, of course, could care less. From my walks with Samson, I learned more about the experiences that mattered to him, and, in doing so, I began to appreciate suburban landscapes in a different way.
I learned that busy places like Main Streets and public parks have a smell history. Huge parking lots can be bleak for all. Samson and I agreed that big-box stores and malls were the worst—visual and olfactory deserts unsuitable for a hike. But a parking lot at Arby’s could be a sacred place.

At least it was for Samson, who generally refused to leave after we sat on the grassy suburban berm and shared a bag of curly fries. After snacks, I would walk with him around the building—along the lane leading to the drive-thru, past the drive-thru window (with faster sniffing because much is dropped there), and around to the back where the exhaust fans are (a kind of climax). This circuit never tired him, and he would tug billy-goat-like on the leash when I tried to get him back into the car. Inevitably, I would have to pick him up, all 75 pounds, and dump him in the backseat.

A dog can sniff fast when there is much to take in, like at a drive-thru window—up to seven times per second. Humans can only take in a new scent about once every two seconds. We have about five million olfactory sense receptors; a bloodhound can have 300 million. A dog can gauge a smell’s strength by its variance between nostrils.

Samson and I had many kinds of walks, the hardest being the “process of elimination” at 7:00 on January mornings. When it was 20 degrees below zero, he always sniffed too long. But sometimes we both liked to linger in a place. We might sit in a park, Samson sniffing with darting nose the scents of other dogs flowing from upwind. With my eyes and ears, I observed things too—where people gathered, the shouts of children, and impromptu soccer games on an open patch of grass.


In an interview with the National Canine Research Council, Horowitz put into words what I intuited from Samson: We need to value our dogs’ “dogness.” This “means appreciating that they get bored, and working to give them things to do; it means celebrating their perceptual abilities, and letting them smell the well-marked spots at length,” she explained.

By following our canine companion’s lead, we two-legged animals can rediscover important things—the fragrances of childhood, so deeply implanted that they seem like they occurred only yesterday. From my walks with Samson, I recalled the smell of leaves burning on an October afternoon; the peonies in June that my mother floated in a crystal bowl; what a pumpkin smells like when you carve it. No matter how boring a place may seem, a dog can open up a new journey. If I’d never had my walks with Samson, I may never have lingered, pausing to discover scents and other creatures hidden in a world we mostly see.

Saturday, March 5, 2016

How Ice Storms May Shape the Future of Forests

In order to study the effects of an ice storm on tree growth, susceptibility to pests and pathogens, changes in habitat for wildlife, a team of researchers created an ice storm at Hubbard Brook Experimental Forest in New Hampshire.
By the Cary Institute of Ecosystem Studies

A team of scientists in New Hampshire recently succeeded in capturing one of nature's most destructive forces - ice - and corralling it in two large research plots on the Hubbard Brook Experimental Forest.
Scientists from the USDA Forest Service, Syracuse University, the Cary Institute of Ecosystem Studies, Cornell University, University of Vermont, and the Hubbard Brook Research Foundation created an experimental ice storm that will improve understanding of short- and long-term effects of ice on northern forests.

Ice storms are a big deal in a changing world. Ice storms are expected to become more frequent and severe in the northeastern United States and eastern Canada as long term climate continues to warm while short term weather patterns still bring blasts of arctic air into the region.

Large Ice storms disrupt lives and damage infrastructure in towns and cities in northern New England, resulting in billions of dollars in damage. Ice storms also literally reshape forests. Heavy ice loads break branches and topple whole trees, resulting in reduced tree growth in ensuing years, increased susceptibility to pests and pathogens, changes in habitat for wildlife, and alterations in how nutrients like carbon and nitrogen cycle in the forest.

"Science is critical to our understanding of how climate change may shape forests in the future," said Tony Ferguson, acting director of the Northern Research Station and the Forest Products Laboratory. "Creating an ice storm is a very unique experiment that would not be possible without all of our partners and funding from the National Science Foundation."

While ice storms are a powerful force in forests, they are also inherently difficult to study because scientists, like citizens, have little lead time on when and where these storms are going to occur. Scientists at the Hubbard Brook Experimental Forest are changing that equation, and instead of waiting for the next big storm to hit, they are creating their own artificial ice storms using high-pressure firefighting pumps and hoses to spray water high up into the forest canopy during a cold snap. They are measuring the obvious and immediate downing of limbs and trees, as well as subtler longer term growth responses, interactions with invasive species, and impacts on forest nutrient cycling.

"This research will provide the scientific community, land managers and the concerned public greater insight on the impacts of these powerful, frightening, and curiously aesthetic extreme winter weather events on ecosystem dynamics in northern hardwood forests," said Lindsey Rustad, team leader at Hubbard Brook Experimental Forest and an investigator on the ice storm experiment.

"Ice storms are a great example of extreme weather events with complex outcomes. The experimental ice storm is part of a comprehensive study of ice storms and their effects at Hubbard Brook, which also includes examining forest recovery from a severe ice storm in 1998, developing and applying models to depict the climate conditions that result in ice storms and forest ecosystem effects, and associated outreach and education," said Charles Driscoll, a professor at Syracuse University and investigator for the Hubbard Brook ice storm experiment.

In addition to Rustad and Driscoll, investigators in the experiment include John Campbell and Paul Schaberg of the USDA Forest Service; Katharine Hayhoe of Texas Tech University, and Sarah Garlick of the Hubbard Brook Research Foundation. Partners include Peter Groffman of the Cary Institute of Ecosystem Studies, Timothy Fahey of Cornell University, and Robert Sanford and Joe Staples of the University of Southern Maine.

The Hubbard Brook Ice Storm Experiment is funded by a grant from the National Science Foundation (DEB-1457675 - Collaborative Research: Understanding the Impacts of Ice Storms on Forest Ecosystems of the Northeastern United States).

The mission of the Forest Service's Northern Research Station is to improve people's lives and help sustain the natural resources in the Northeast and Midwest through leading-edge science and effective information delivery.

The mission of the Forest Service, part of the U.S. Department of Agriculture, is to sustain the health, diversity, and productivity of the Nation's forests and grasslands to meet the needs of present and future generations. The agency manages 193 million acres of public land, provides assistance to state and private landowners, and maintains the largest forestry research organization in the world.

Public lands the Forest Service manages contribute more than $13 billion to the economy each year through visitor spending alone. Those same lands provide 20 percent of the nation's clean water supply, a value estimated at $7.2 billion per year. The agency has either a direct or indirect role in stewardship of about 80 percent of the 850 million forested acres within the U.S., of which 100 million acres are urban forests where most Americans live.

How Ice Storms May Shape the Future of Forests

Sunday, February 21, 2016

Trees Have Social Networks, Too

“When I say, ‘Trees suckle their children,’ everyone knows immediately what I mean.” PETER WOHLLEBEN Credit Gordon Welters for The New York Times
 HÜMMEL, Germany — IN the deep stillness of a forest in winter, the sound of footsteps on a carpet of leaves died away. Peter Wohlleben had found what he was looking for: a pair of towering beeches. “These trees are friends,” he said, craning his neck to look at the leafless crowns, black against a gray sky. “You see how the thick branches point away from each other? That’s so they don’t block their buddy’s light.”
Before moving on to an elderly beech to show how trees, like people, wrinkle as they age, he added, “Sometimes, pairs like this are so interconnected at the roots that when one tree dies, the other one dies, too.”
Mr. Wohlleben, 51, is a very tall career forest ranger who, with his ramrod posture and muted green uniform, looks a little like one of the sturdy beeches in the woods he cares for. Yet he is lately something of a sensation as a writer in Germany, a place where the forest has long played an outsize role in the cultural consciousness, in places like fairy tales, 20th-century philosophy, Nazi ideology and the birth of the modern environmental movement.
Mr. Wohlleben traces his love of the forest to his early childhood, where he raised spiders and turtles. In high school, teachers painted a dire picture of the world’s ecological future, and he decided it was his mission to help. Credit Gordon Welters for The New York Times
After the publication in May of Mr. Wohlleben’s book, a surprise hit titled “The Hidden Life of Trees: What They Feel, How They Communicate — Discoveries From a Secret World,” the German forest is back in the spotlight. Since it first topped best-seller lists last year, Mr. Wohlleben has been spending more time on the media trail and less on the forest variety, making the case for a popular reimagination of trees, which, he says, contemporary society tends to look at as “organic robots” designed to produce oxygen and wood.

Presenting scientific research and his own observations in highly anthropomorphic terms, the matter-of-fact Mr. Wohlleben has delighted readers and talk-show audiences alike with the news — long known to biologists — that trees in the forest are social beings. They can count, learn and remember; nurse sick neighbors; warn each other of danger by sending electrical signals across a fungal network known as the “Wood Wide Web”; and, for reasons unknown, keep the ancient stumps of long-felled companions alive for centuries by feeding them a sugar solution through their roots.

“With his book, he changed the way I look at the forest forever,” Markus Lanz, a popular talk show host, said in an email. “Every time I walk through a beautiful woods, I think about it.”

Though duly impressed with Mr. Wohlleben’s ability to capture the public’s attention, some German biologists question his use of words, like “talk” rather than the more standard “communicate,” to describe what goes on between trees in the forest.

But this, says Mr. Wohlleben, who invites readers to imagine what a tree might feel when its bark tears (“Ouch!”), is exactly the point. “I use a very human language,” he explained. “Scientific language removes all the emotion, and people don’t understand it anymore. When I say, ‘Trees suckle their children,’ everyone knows immediately what I mean.”
Still No. 1 on the Spiegel best-seller list for nonfiction, “Hidden Life” has sold 320,000 copies and has been optioned for translation in 19 countries (Canada’s Greystone Books will publish an English version in September). “It’s one of the biggest successes of the year,” said Denis Scheck, a German literary critic who praised the humble narrative style and the book’s ability to awaken in readers an intense, childlike curiosity about the workings of the world.

The popularity of “The Hidden Life of Trees,” Mr. Scheck added, says less about Germany than it does about modern life. People who spend most of their time in front of computers want to read about nature. “Germans are reputed to have a special relationship with the forest, but it’s kind of a cliché,” Mr. Scheck said. “Yes, there’s Hansel and Gretel, and, sure, if your marriage fails, you go for a long hike in the woods. But I don’t think Germans love their forest more than Swedes or Norwegians or Finns.”

Mr. Wohlleben traces his own love of the forest to his early childhood. Growing up in the 1960s and ’70s in Bonn, then the West German capital, he raised spiders and turtles, and liked playing outside more than any of his three siblings did. In high school, a generation of young, left-leaning teachers painted a dire picture of the world’s ecological future, and he decided it was his mission to help.

He studied forestry, and began working for the state forestry administration in Rhineland-Palatinate in 1987. Later, as a young forester in charge of a 3,000-odd acre woodlot in the Eifel region, about an hour outside Cologne, he felled old trees and sprayed logs with insecticides. But he did not feel good about it: “I thought, ‘What am I doing? I’m making everything kaput.’ ”

Reading up on the behavior of trees — a topic he learned little about in forestry school — he found that, in nature, trees operate less like individuals and more as communal beings. Working together in networks and sharing resources, they increase their resistance.

By artificially spacing out trees, the plantation forests that make up most of Germany’s woods ensure that trees get more sunlight and grow faster. But, naturalists say, creating too much space between trees can disconnect them from their networks, stymieing some of their inborn resilience mechanisms.

Intrigued, Mr. Wohlleben began investigating alternate approaches to forestry. Visiting a handful of private forests in Switzerland and Germany, he was impressed. “They had really thick, old trees,” he said. “They treated their forest much more lovingly, and the wood they produced was more valuable. In one forest, they said, when they wanted to buy a car, they cut two trees. For us, at the time, two trees would buy you a pizza.”

Back in the Eifel in 2002, Mr. Wohlleben set aside a section of “burial woods,” where people could bury cremated loved ones under 200-year-old trees with a plaque bearing their names, bringing in revenue without harvesting any wood. The project was financially successful. But, Mr. Wohlleben said, his bosses were unhappy with his unorthodox activities. He wanted to go further — for example, replacing heavy logging machinery, which damages forest soil, with horses — but could not get permission.

After a decade of struggling with his higher-ups, he decided to quit. “I consulted with my family first,” said Mr. Wohlleben, who is married and has two children. Though it meant giving up the ironclad security of employment as a German civil servant, “I just thought, ‘I cannot do this the rest of my life.’” The family planned to emigrate to Sweden. But it turned out that Mr. Wohlleben had won over the forest’s municipal owners.

So, 10 years ago, the municipality took a chance. It ended its contract with the state forestry administration, and hired Mr. Wohlleben directly. He brought in horses, eliminated insecticides and began experimenting with letting the woods grow wilder. Within two years, the forest went from loss to profit, in part by eliminating expensive machinery and chemicals.

Despite his successes, in 2009 Mr. Wohlleben started having panic attacks. “I kept thinking, ‘Ah! You only have 20 years, and you still have to accomplish this, and this, and that.’” He began therapy, to treat burnout and depression. It helped. “I learned to be happy about what I’ve done so far,” he said. “With a forest, you have to think in terms of 200 or 300 years. I learned to accept that I can’t do everything. Nobody can.” He wanted to write “The Hidden Life of Trees” to show laypeople how great trees are.

Stopping to consider a tree that rose up straight then curved like a question mark, Mr. Wohlleben said, however, that it was the untrained perspective of visitors he took on forest tours years ago to which he owed much insight.

“For a forester, this tree is ugly, because it is crooked, which means you can’t get very much money for the wood,” he said. “It really surprised me, walking through the forest, when people called a tree like this one beautiful. They said, ‘My life hasn’t always run in a straight line, either.’ And I began to see things with new eyes.” 

Monday, February 15, 2016

Street Trees Really Do Make People Healthier

Jason G. Goldman

It’s easy enough to claim that being in nature makes people feel better. It certainly feels like it’s true. A weekend in the mountains, or even a few hours in a park after a long day at work, truly feels like it is somehow restorative.

There are some good reasons to believe that green space could have a causal relationship with health and happiness. For one thing, trees scrub pollution from the skies, allowing those nearby to breathe cleaner air. Exposure to nature has also been linked with reduced blood pressure and stress, and it seems to motivate folks to become more active and less sedentary. Then there’s the Japanese practice of shinrinyoku, or “forest bathing.” The Japanese believe that what essentially amounts to a nature walk promotes human health and wellbeing. Plants are also part of a complex food web that, together, provides things critical to our survival like oxygen to breathe, fresh water to drink, and food to eat. Even if all these things are true – and they probably are – that still doesn’t mean that it’s nature, per se, that’s having the apparent health benefit.

To make that claim we need real, quantifiable data. That’s where University of Chicago psychology graduate student Omid Kardan and University of Chicago professor Marc G. Berman come in. They and their colleagues looked to Toronto, Canada, a city for which there is plenty of satellite imagery (which allows them to measure green spaces) and self-reported health information through the Ontario Health Study. By using a set of common statistical techniques, the researchers were able to really see whether there’s anything to the idea that greenery makes people healthier.

But it wasn’t green spaces in general they were interested in; it was trees in particular. By leaving lawns and bushes out, the researchers hoped to zero in on what they thought was “potentially the most important component for having beneficial effects.” First, they took data on trees from two databases maintained by the city of Toronto: “Street Tree General Data” and “Forest and Land Cover.” Together, those databases provided information on street trees as well as those in parks and backyards. They chose Toronto in part to rule out the effects of health insurance; unlike in the US, Canadians are guaranteed universal publically funded healthcare, regardless of employment status or income level. Still, despite equal access, not all Canadians choose to avail themselves of healthcare in equal ways. Indeed, those with lower incomes and fewer years of schooling tend to see doctors less often, which is why the researchers made note of that sort of demographic data.

They found that those who live in areas with more street trees reported better health perception than those in neighborhoods with fewer trees. Regardless of their actual health, they felt they were healthier. But it turns out they were actually healthier too: they suffered from fewer cardio-metabolic conditions.

But that’s not all. To really drive the point home, Kardan reduced the findings to cold, hard cash.

His team found that by planting 10 more trees per city block, Toronto could improve health perception as much as if every household on that same block earned $10,000 more every year, or magically became seven years younger.

The results were even more striking for actual health. Planting just 11 more trees per city block would reduce cardio-metabolic conditions the same extent as if everybody living on that block earned $20,000 more each year or somehow became 1.4 years younger.

So what’s the secret? Kardan doesn’t know, and his study isn’t explicitly designed to get at the underlying mechanism. But a close look at the data offers up a suggestion. It wasn’t proximity to trees in a neighborhood that was the most important variable, but the number of trees on the streets. That suggests that it’s not necessarily that the trees are themselves providing important services (they do that, though that might not be what accounts for these health effects). Instead, it could be something as simple as peoples’ ability to literally see trees, and the most common place for most people to see trees is on the street. It’s also possible that street trees are disproportionately responsible for capturing street pollution, and that could be driving the team’s findings.

Maintaining a street tree for a year costs between $30 and $500, depending on where it is. In other words, planting ten or eleven trees per city block would be far cheaper than paying everyone $10,000-20,000 more each year. That should be good news for city planners.