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.”

http://www.nytimes.com/2016/01/30/world/europe/german-forest-ranger-finds-that-trees-have-social-networks-too.html?_r=0 

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.

http://conservationmagazine.org/2015/07/street-trees-really-do-make-people-healthier/