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London is a forest, and this map explores its trees
TreeTalk finds rare arboreal treasures among London's common foliage.
- 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
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.
A rather rarer import from Wuhan: the Chinese photinia.
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
A tree walk starting and finishing at Cavendish Square, a leafy refuge just off Oxford Circus.
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.
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.
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 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
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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Got a strange map? Let me know at firstname.lastname@example.org.
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Certain water beetles can escape from frogs after being consumed.
- A Japanese scientist shows that some beetles can wiggle out of frog's butts after being eaten whole.
- The research suggests the beetle can get out in as little as 7 minutes.
- Most of the beetles swallowed in the experiment survived with no complications after being excreted.
In what is perhaps one of the weirdest experiments ever that comes from the category of "why did anyone need to know this?" scientists have proven that the Regimbartia attenuata beetle can climb out of a frog's butt after being eaten.
The research was carried out by Kobe University ecologist Shinji Sugiura. His team found that the majority of beetles swallowed by black-spotted pond frogs (Pelophylax nigromaculatus) used in their experiment managed to escape about 6 hours after and were perfectly fine.
"Here, I report active escape of the aquatic beetle R. attenuata from the vents of five frog species via the digestive tract," writes Sugiura in a new paper, adding "although adult beetles were easily eaten by frogs, 90 percent of swallowed beetles were excreted within six hours after being eaten and, surprisingly, were still alive."
One bug even got out in as little as 7 minutes.
Sugiura also tried putting wax on the legs of some of the beetles, preventing them from moving. These ones were not able to make it out alive, taking from 38 to 150 hours to be digested.
Naturally, as anyone would upon encountering such a story, you're wondering where's the video. Thankfully, the scientists recorded the proceedings:
The Regimbartia attenuata beetle can be found in the tropics, especially as pests in fish hatcheries. It's not the only kind of creature that can survive being swallowed. A recent study showed that snake eels are able to burrow out of the stomachs of fish using their sharp tails, only to become stuck, die, and be mummified in the gut cavity. Scientists are calling the beetle's ability the first documented "active prey escape." Usually, such travelers through the digestive tract have particular adaptations that make it possible for them to withstand extreme pH and lack of oxygen. The researchers think the beetle's trick is in inducing the frog to open a so-called "vent" controlled by the sphincter muscle.
"Individuals were always excreted head first from the frog vent, suggesting that R. attenuata stimulates the hind gut, urging the frog to defecate," explains Sugiura.
For more information, check out the study published in Current Biology.
The design of a classic video game yields insights on how to address global poverty.
Poverty can be a self-sustaining cycle that might require an external influence to break it. A new paper published in Nature Sustainability and written by professor Andrew Bell of Boston University suggests that we could improve global anti-poverty and economic development systems by turning to an idea in a video game about a race car-driving Italian plumber.
A primer on Mario Kart
For those who have not played it, Mario Kart is a racing game starring Super Mario and other characters from the video game franchise that bears his name. Players race around tracks collecting power-ups that can directly help them, such as mushrooms that speed up their karts, or slow down other players, such as heat-seeking turtle shells that momentarily crash other karts.
The game is well known for having a mechanism known as "rubber-banding." Racers in the front of the pack get wimpy power-ups, like banana peels to slip up other karts, while those toward the back get stronger ones, like golden mushrooms that provide extra long speed boosts. The effect of this is that those in the back are pushed towards the center, and those in front don't get any boosts that would make catching them impossible.
If you're in last, you might get the help you need to make a last-minute break for the lead. If you're in first, you have to be on the lookout for these breakouts (and the ever-dreaded blue shells). The game remains competitive and fun.
Rubber-banding: A moral and economic lesson from Mario Kart
In the real world, we see rubber-banding used all the time. Welfare systems tend to provide more aid to those who need it than those who do not. Many of them are financed by progressive taxation, which is heavier on the well-off than the down-and-out. Some research suggests that these do work, as countries with lower levels of income inequality have higher social mobility levels.
It is a little more difficult to use rubber-banding in real life than in a video game, of course. While in the game, it is easy to decide who is doing well and who is not, things can be a little more muddled in reality. Furthermore, while those in a racing game are necessarily antagonistic to each other, real systems often strive to improve conditions for everybody or to reach common goals.
As Bell points out, rubber-banding can also be used to encourage sustainable, growth programs that help the poor other than welfare. They point out projects such as irrigation systems in Pakistan or Payments for Ecosystems Services (PES) schemes in Malawi, which utilize positive feedback loops to both provide aid to the poor and promote stable systems that benefit everyone.
Rubber-banding feedback loops in different systems. Mario Kart (a), irrigation systems in Pakistan (b), and PES operations in Malawi (c) are shown. Links between one better-off (blue) and one worse-off (red) individual are highlighted. Feedback in Mario Kart (a), designed to balance the racers, imprAndrew Bell/ Nature Sustainability
In the Malawi case, farmers were paid to practice conservation agriculture to reduce the amount of sediment from their farms flowing into a river. This immediately benefits hydroelectric producers and their customers but also provides real benefits to farmers in the long run as their soil doesn't erode. By providing an incentive to the farmers to conserve the soil, a virtuous cycle of conservation, soil improvement, and improved yields can begin.
While this loop differs from the rubber-banding in Mario, the game's approach can help illustrate the benefits of rubber-banding in achieving a more equitable world.
The task now, as Bell says in his paper, is to look at problems that exist and find out "what the golden mushroom might be."
Satellite imagery can help better predict volcanic eruptions by monitoring changes in surface temperature near volcanoes.
- A recent study used data collected by NASA satellites to conduct a statistical analysis of surface temperatures near volcanoes that erupted from 2002 to 2019.
- The results showed that surface temperatures near volcanoes gradually increased in the months and years prior to eruptions.
- The method was able to detect potential eruptions that were not anticipated by other volcano monitoring methods, such as eruptions in Japan in 2014 and Chile in 2015.
How can modern technology help warn us of impending volcanic eruptions?
One promising answer may lie in satellite imagery. In a recent study published in Nature Geoscience, researchers used infrared data collected by NASA satellites to study the conditions near volcanoes in the months and years before they erupted.
The results revealed a pattern: Prior to eruptions, an unusually large amount of heat had been escaping through soil near volcanoes. This diffusion of subterranean heat — which is a byproduct of "large-scale thermal unrest" — could potentially represent a warning sign of future eruptions.
Conceptual model of large-scale thermal unrestCredit: Girona et al.
For the study, the researchers conducted a statistical analysis of changes in surface temperature near volcanoes, using data collected over 16.5 years by NASA's Terra and Aqua satellites. The results showed that eruptions tended to occur around the time when surface temperatures near the volcanoes peaked.
Eruptions were preceded by "subtle but significant long-term (years), large-scale (tens of square kilometres) increases in their radiant heat flux (up to ~1 °C in median radiant temperature)," the researchers wrote. After eruptions, surface temperatures reliably decreased, though the cool-down period took longer for bigger eruptions.
"Volcanoes can experience thermal unrest for several years before eruption," the researchers wrote. "This thermal unrest is dominated by a large-scale phenomenon operating over extensive areas of volcanic edifices, can be an early indicator of volcanic reactivation, can increase prior to different types of eruption and can be tracked through a statistical analysis of little-processed (that is, radiance or radiant temperature) satellite-based remote sensing data with high temporal resolution."
Temporal variations of target volcanoesCredit: Girona et al.
Although using satellites to monitor thermal unrest wouldn't enable scientists to make hyper-specific eruption predictions (like predicting the exact day), it could significantly improve prediction efforts. Seismologists and volcanologists currently use a range of techniques to forecast eruptions, including monitoring for gas emissions, ground deformation, and changes to nearby water channels, to name a few.
Still, none of these techniques have proven completely reliable, both because of the science and the practical barriers (e.g. funding) standing in the way of large-scale monitoring. In 2014, for example, Japan's Mount Ontake suddenly erupted, killing 63 people. It was the nation's deadliest eruption in nearly a century.
In the study, the researchers found that surface temperatures near Mount Ontake had been increasing in the two years prior to the eruption. To date, no other monitoring method has detected "well-defined" warning signs for the 2014 disaster, the researchers noted.
The researchers hope satellite-based infrared monitoring techniques, combined with existing methods, can improve prediction efforts for volcanic eruptions. Volcanic eruptions have killed about 2,000 people since 2000.
"Our findings can open new horizons to better constrain magma–hydrothermal interaction processes, especially when integrated with other datasets, allowing us to explore the thermal budget of volcanoes and anticipate eruptions that are very difficult to forecast through other geophysical/geochemical methods."