[chidg]

Although this is a great piece of public art, it's worth noting that the pollution they refer to is really only particulate matter, with some effect on nitrogen oxides. These mosses would be far less effective at scrubbing CO2 than a 'regular' tree.

You could get a pretty similar effect by installing a mechanical air filter and planting some trees.

[Bheliar]

Can you give a study for this? And plants, no matter which, obviously have other benefits than cleaning compared to an artificial filter. Seeing nature, even on screen, boosts human health. https://environhealthprevmed.biomedcentral.com/articles/10.1... Another important factor of trees is their ability to cool down the city. Moss might not be able to provide the shade the trees offer, but they can provide a cooling effect a simple filter could not provide. Apart from that, while trees are awesome, they take a long time to grow, and a lot of resources during that time. Moss is easier to farm and therefore can be easier to replace if it dies. And no matter how well tended a tree is: A city is a hard place for trees. And taking climate change into account, it will get even harder. Trees that were once fitting for a city might not do well there anymore. And I dont think the moss trees are supposed to exist instead of actual trees. They are instead a great way to boost a citys health next to actual trees and to fill gaps where trees are missing or have been newly planted. So why use trees and mechanical filters, when you can get trees and moss?