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Ever wondered which trees are best at tackling London’s pollution?

Well, turns out, the majority of London’s aren’t that great

Written by
Rhys Thomas

Trees are nice, aren’t they? Big, fluffy, spiky, leafy, green things (sometimes orange and pink) that stick out against London’s moody old grey backdrop of concrete, steel and glass. Nature’s pop of colour, if you will. They’re a good time. Though they do always look a bit outnumbered by buildings in the city, London does surprisingly well when it comes to greenery. 

Just over a fifth of London is covered in trees, apparently. This makes London technically a forest, going on a definition from the UN. However, there’s a lot more the city needs to do if it wants to clean up the air and make a better living environment for animals, plants and us humans. The aim is to get tree coverage up to 30 percent by 2050, according to Sadiq Khan, Mayor of London

So the question is, what trees do we wanna plant? The pretty ones? No! Well, maybe. But only if they’re gonna be as useful as possible. You see, all trees are made differently. Some filter the air better than others, for example. So what’s the best type of tree for London? Well, it might be conifers. 

If you don’t know your horse chestnut from your hornbeam, conifers are a group of cone-bearing seed plants. They’re usually spiky and triangular: think Christmas trees. Within this category, pine trees, oak trees and common yew are among the most effective at cleaning the air, according to Prashant Kumar, the founding director of the Global Centre for Clean Air Research at the University of Surrey. He spoke to the BBC about the subject in 2020. Conifers also have the benefit of being evergreen, meaning they can work on the air 365 days a year. 

It isn’t just purifying the air that trees are good at. They’re also a dab hand at removing particulate matter (PM) from the atmosphere. What’s that? It’s the name for tiny particles of chemicals, acids, dust and metals that typically get emitted by transport, factories and all the other nasty-emission-creating things around the Big Smoke.

Different trees have different jobs, though, and there are more jobs that we need the trees to help with than you could shake a stick at (it would be kinda messed up to do that to its own family anyway, so don’t). This means that while them conifers are great for purifying the air, where things like particulate matter are concerned, silver birch, yew, and elder trees are top dogs. There’s also the question of where is the best place to plant these trees, but you can have a go at settling that bit down the pub sometime. 

For every good egg (or log and leaf boi) though, there’s a less good option. The troubling trees that used to throw rubbers at you in class exist too. These are trees that spit out VOCs (volatile organic compounds): they do it to repel insects among other things. Them compounds aren’t good, because they damage the ozone layer. Poplars and oaks are prime examples of this, and London has loads of them. 

Also, just because it’s kinda fun, if you fancy having a browse of which trees are planted where in the city, this map from the government has the information you need. You can also filter which tress you want to see. Procrastination? You betcha. 

Londoners might be asked to wear pollution monitors.

Here’s what you need to know about London’s new ULEZ expansion.

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