London is a forest, and this map explores its trees

TreeTalk finds rare arboreal treasures among London's common foliage.

London Norway maple map

One of London's many thousand Norway maples, just one of over 600 tree species gathered on this interactive map.

Image: TreeTalk
  • The world's largest urban forest, London counts nearly as many trees as it does people.
  • TreeTalk identifies about 700,000 of them, both common species and rarities.
  • Explore them yourself, or have the algorithm pick out a route from a starting point of your choice.

World's largest urban forest

\u200bView of London from Sawyer's Hill in Richmond Park.

View of London from Sawyer's Hill in Richmond Park.

Image: Maxwell Hamilton, CC BY 2.0

Did you know that London qualifies as a forest? The UN's Food and Agriculture Organization defines a forest as a contiguous area with at least 10 percent tree canopy cover. Greater London's trees manage more than double that (21 percent).

But then there are no less than 8.4 million of the leafy bastards standing around London's 600 square miles – that's almost one for every Londoner. So, it's not entirely surprising that London is, according to the UK's own Forestry Commission, 'the world's largest urban forest.'

Similar to its human inhabitants, London's trees are a cosmopolitan bunch with origins all over the world. No British city has a wider diversity of tree species. You can now explore that diversity in all its glory thanks to TreeTalk, a web page which identifies 700,000 individual trees throughout Greater London and generates tree walks from the starting point of your choice.

If you're currently confined to Britain's metropolis, the web page – also available as a smartphone app (Android only for now) – is an interesting way to spice up your daily exercise walks and learn a bit about your immediate surroundings. And if you're a London junkie pandemically deprived of a visit, TreeTalk offers a novel way to virtually stroll through your favorite city.

Gold-category rarities

A rather rarer import from Wuhan: the Chinese photinia.

A rather rarer import from Wuhan: the Chinese photinia.

Image: TreeTalk

Zoom in and click on any tree; or type in an address or postal code to auto-generate a walking tour of the area. You'll find species that are common as muck, and with just a little bit of luck you'll come across trees in three categories of rarity: bronze (less than 400 specimens throughout the city), silver (75 or less), and gold (10 or less).

For example, go to Westbourne Gardens, in West London's Paddington area: there you'll find the only four specimens of the Chinese photinia that TreeTalk has identified so far in all of London. Widely used as a greening plant in Chinese cities, the tree is omnipresent along all major avenues in Wuhan – yes, that Wuhan.

Yet Wuhanites are less than keen on the semen-like smell its flowers spread each spring, and some have called for the trees to be replaced. No such complaints seem to have been registered yet by the photinias' Paddingtonian neighbors.

Older than the dinosaurs

\u200bA tree walk starting and finishing at Cavendish Square, a leafy refuge just off Oxford Circus.

A tree walk starting and finishing at Cavendish Square, a leafy refuge just off Oxford Circus.

Image: TreeTalk

Another example: set your sights on lovely Cavendish Square, a small park just off busy Oxford Circus popular with office workers on their lunch break. The square is dominated by London planes (#20 on the map), one of the more common street trees in Central London.

TreeTalk's auto-generated route around the area leads past common trees like the ash (#1), the chanticleer pear (#3) and the fastigiate Norwegian maple (#6), but also along such rarities as the monkey puzzle tree (#9; only 32 found so far in London), the hackberry (#17; and only 17 in London) and the variegated wedding cake tree (#11; only 15 in London).

Less rare but still remarkable are a ginkgo (#4), a species older than the dinosaurs; one of less than 200 olive trees in London (#12); and the tree of heaven (#16), also known as the 'ghetto palm', because it thrives on wasteland.

From A to B

A walk south of the river, past some of London's rare and common tree species.

A walk south of the river, past some of London's rare and common tree species.

Image: TreeTalk

Yet another option: pick an A and a B, and see which trees connect your walk between both points. Like this amble from London Bridge to Parliament Square, along omnipresent species (and their variants) like ash (#1), lime (#2, #5), maple (#4, #7, #13), birch (#14), and cherry (#16, #17), and rarer ones like the box elder (#3), the Japanese privet (#9), and the Portuguese laurel (#11) – only two of which have been identified in London.

#20 on this walk is, again, a London plane. Ubiquitous in the center, this tree is considered 'native' to the city, but its past is a bit more complicated than that. The species was discovered in the 17th century in a nursery garden in Vauxhall, on the south bank of the Thames.


\u200bLondon planes in Berkeley Square.

London planes in Berkeley Square.

Image: Justinc, CC BY-SA 2.0

'Discovered' is the right word, as it was unknown before. The London plane may be a hybrid between an Oriental plane, brought to Britain in the 16th century, and an American sycamore, imported in the early 17th century. One of each was indeed present in that Vauxhall nursery.

As it turned out, the 'new' species was well suited to its urban environment: it's not too picky with regard to soil, it requires little root space, and its flaky bark easily sheds pollutants. It flourishes despite pollarding and can grow up to 30 meters tall.

Because of those qualities, the London plane was chosen for mass plantings across the city, to provide much-needed greenery during its rapid expansion in the 19th century. But the London plane is not just hardy, it's also quite ornamental. The 30-odd specimens planted in Berkeley Square in 1789 are among the oldest and grandest in London.

Why 'leafy' means 'affluent'

Trees are useful, valuable and pleasant assets for any city.

Trees are useful, valuable and pleasant assets for any city.

Image: TreeTalk

Trees are an important asset to any city, and not just for their grandeur. They provide shade and prevent flooding, store carbon, and help cool nearby buildings. A recent iTree study figures that London's trees suck out 2,261 tons of pollution from the air each year and that their total environmental benefit amounts to about £132.7 ($164.6) million per year.

But grandeur also counts for something. Literally, in fact: It's been shown that tree-lined streets boost house prices by as much as 15 percent. No wonder 'leafy' is code for 'affluent'.

Despite its iconic status, the London plane is not the city's most prevalent species. In Inner London, it's birch (12 percent), followed by lime (6 percent) and apple (6 percent) trees. Sycamore (8 percent), English oak (8 percent) and hawthorn (7 percent) are the most common in Outer London.

The iTree study recorded 126 species, not counting the 2,000 species and varieties found at Kew Gardens.

Thomas Hardy's handiwork

\u200bThe Hardy Tree: 'designed' by Thomas Hardy, before he turned his hand at writing.

The Hardy Tree: 'designed' by Thomas Hardy, before he turned his hand at writing.

Image: cisko66, CC BY 3.0

For its part, TreeTalk describes more than 600 species, but it is far from complete. It provides information on just 700,000 specimens – not even 10 percent of Greater London's overall total. That's because some of London's 33 boroughs have not yet or not completely provided data on the trees in their area.

For another take on London's arboreal heritage, check out the Great Trees of London, a collection of 54 of the city's most remarkable trees, as chosen by the Londoners themselves.

This list was born in the aftermath of the Great Storm of 1987, which felled around 15 million trees across the country. The Countryside Commission selected 41 much-loved survivors suggested by the public, a list that was later expanded to 61 – sadly, six trees have since been lost.

They include such venerable ancients as the Royal Oak of Richmond Park, which is around 750 years old; the Hardy Tree at St Pancras Old Church, surrounded by a macabre arrangement of decommissioned gravestones; one of the London planes in Berkeley Square; and the Totteridge Yew, which may be more than 2,000 years old – older than London itself.

Strange Maps #1028

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CT scans of shark intestines find Nikola Tesla’s one-way valve

Evolution proves to be just about as ingenious as Nikola Tesla

Credit: Gerald Schömbs / Unsplash
Surprising Science
  • For the first time, scientists developed 3D scans of shark intestines to learn how they digest what they eat.
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Are we really addicted to technology?

Fear that new technologies are addictive isn't a modern phenomenon.

Credit: Rodion Kutsaev via Unsplash
Technology & Innovation

This article was originally published on our sister site, Freethink, which has partnered with the Build for Tomorrow podcast to go inside new episodes each month. Subscribe here to learn more about the crazy, curious things from history that shaped us, and how we can shape the future.

In many ways, technology has made our lives better. Through smartphones, apps, and social media platforms we can now work more efficiently and connect in ways that would have been unimaginable just decades ago.

But as we've grown to rely on technology for a lot of our professional and personal needs, most of us are asking tough questions about the role technology plays in our own lives. Are we becoming too dependent on technology to the point that it's actually harming us?

In the latest episode of Build for Tomorrow, host and Entrepreneur Editor-in-Chief Jason Feifer takes on the thorny question: is technology addictive?

Popularizing medical language

What makes something addictive rather than just engaging? It's a meaningful distinction because if technology is addictive, the next question could be: are the creators of popular digital technologies, like smartphones and social media apps, intentionally creating things that are addictive? If so, should they be held responsible?

To answer those questions, we've first got to agree on a definition of "addiction." As it turns out, that's not quite as easy as it sounds.

If we don't have a good definition of what we're talking about, then we can't properly help people.


"Over the past few decades, a lot of effort has gone into destigmatizing conversations about mental health, which of course is a very good thing," Feifer explains. It also means that medical language has entered into our vernacular —we're now more comfortable using clinical words outside of a specific diagnosis.

"We've all got that one friend who says, 'Oh, I'm a little bit OCD' or that friend who says, 'Oh, this is my big PTSD moment,'" Liam Satchell, a lecturer in psychology at the University of Winchester and guest on the podcast, says. He's concerned about how the word "addiction" gets tossed around by people with no background in mental health. An increased concern surrounding "tech addiction" isn't actually being driven by concern among psychiatric professionals, he says.

"These sorts of concerns about things like internet use or social media use haven't come from the psychiatric community as much," Satchell says. "They've come from people who are interested in technology first."

The casual use of medical language can lead to confusion about what is actually a mental health concern. We need a reliable standard for recognizing, discussing, and ultimately treating psychological conditions.

"If we don't have a good definition of what we're talking about, then we can't properly help people," Satchell says. That's why, according to Satchell, the psychiatric definition of addiction being based around experiencing distress or significant family, social, or occupational disruption needs to be included in any definition of addiction we may use.

Too much reading causes... heat rashes?

But as Feifer points out in his podcast, both popularizing medical language and the fear that new technologies are addictive aren't totally modern phenomena.

Take, for instance, the concept of "reading mania."

In the 18th Century, an author named J. G. Heinzmann claimed that people who read too many novels could experience something called "reading mania." This condition, Heinzmann explained, could cause many symptoms, including: "weakening of the eyes, heat rashes, gout, arthritis, hemorrhoids, asthma, apoplexy, pulmonary disease, indigestion, blocking of the bowels, nervous disorder, migraines, epilepsy, hypochondria, and melancholy."

"That is all very specific! But really, even the term 'reading mania' is medical," Feifer says.

"Manic episodes are not a joke, folks. But this didn't stop people a century later from applying the same term to wristwatches."

Indeed, an 1889 piece in the Newcastle Weekly Courant declared: "The watch mania, as it is called, is certainly excessive; indeed it becomes rabid."

Similar concerns have echoed throughout history about the radio, telephone, TV, and video games.

"It may sound comical in our modern context, but back then, when those new technologies were the latest distraction, they were probably really engaging. People spent too much time doing them," Feifer says. "And what can we say about that now, having seen it play out over and over and over again? We can say it's common. It's a common behavior. Doesn't mean it's the healthiest one. It's just not a medical problem."

Few today would argue that novels are in-and-of-themselves addictive — regardless of how voraciously you may have consumed your last favorite novel. So, what happened? Were these things ever addictive — and if not, what was happening in these moments of concern?

People are complicated, our relationship with new technology is complicated, and addiction is complicated — and our efforts to simplify very complex things, and make generalizations across broad portions of the population, can lead to real harm.


There's a risk of pathologizing normal behavior, says Joel Billieux, professor of clinical psychology and psychological assessment at the University of Lausanne in Switzerland, and guest on the podcast. He's on a mission to understand how we can suss out what is truly addictive behavior versus what is normal behavior that we're calling addictive.

For Billieux and other professionals, this isn't just a rhetorical game. He uses the example of gaming addiction, which has come under increased scrutiny over the past half-decade. The language used around the subject of gaming addiction will determine how behaviors of potential patients are analyzed — and ultimately what treatment is recommended.

"For a lot of people you can realize that the gaming is actually a coping (mechanism for) social anxiety or trauma or depression," says Billieux.

"Those cases, of course, you will not necessarily target gaming per se. You will target what caused depression. And then as a result, If you succeed, gaming will diminish."

In some instances, a person might legitimately be addicted to gaming or technology, and require the corresponding treatment — but that treatment might be the wrong answer for another person.

"None of this is to discount that for some people, technology is a factor in a mental health problem," says Feifer.

"I am also not discounting that individual people can use technology such as smartphones or social media to a degree where it has a genuine negative impact on their lives. But the point here to understand is that people are complicated, our relationship with new technology is complicated, and addiction is complicated — and our efforts to simplify very complex things, and make generalizations across broad portions of the population, can lead to real harm."

Behavioral addiction is a notoriously complex thing for professionals to diagnose — even more so since the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the book professionals use to classify mental disorders, introduced a new idea about addiction in 2013.

"The DSM-5 grouped substance addiction with gambling addiction — this is the first time that substance addiction was directly categorized with any kind of behavioral addiction," Feifer says.

"And then, the DSM-5 went a tiny bit further — and proposed that other potentially addictive behaviors require further study."

This might not sound like that big of a deal to laypeople, but its effect was massive in medicine.

"Researchers started launching studies — not to see if a behavior like social media use can be addictive, but rather, to start with the assumption that social media use is addictive, and then to see how many people have the addiction," says Feifer.

Learned helplessness

The assumption that a lot of us are addicted to technology may itself be harming us by undermining our autonomy and belief that we have agency to create change in our own lives. That's what Nir Eyal, author of the books Hooked and Indistractable, calls 'learned helplessness.'

"The price of living in a world with so many good things in it is that sometimes we have to learn these new skills, these new behaviors to moderate our use," Eyal says. "One surefire way to not do anything is to believe you are powerless. That's what learned helplessness is all about."

So if it's not an addiction that most of us are experiencing when we check our phones 90 times a day or are wondering about what our followers are saying on Twitter — then what is it?

"A choice, a willful choice, and perhaps some people would not agree or would criticize your choices. But I think we cannot consider that as something that is pathological in the clinical sense," says Billieux.

Of course, for some people technology can be addictive.

"If something is genuinely interfering with your social or occupational life, and you have no ability to control it, then please seek help," says Feifer.

But for the vast majority of people, thinking about our use of technology as a choice — albeit not always a healthy one — can be the first step to overcoming unwanted habits.

For more, be sure to check out the Build for Tomorrow episode here.

Why the U.S. and Belgium are culture buddies

The Inglehart-Welzel World Cultural map replaces geographic accuracy with closeness in terms of values.

According to the latest version of the Inglehart-Welzel World Cultural Map, Belgium and the United States are now each other's closest neighbors in terms of cultural values.

Credit: World Values Survey, public domain.
Strange Maps
  • This map replaces geography with another type of closeness: cultural values.
  • Although the groups it depicts have familiar names, their shapes are not.
  • The map makes for strange bedfellows: Brazil next to South Africa and Belgium neighboring the U.S.
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