A new study by Columbia University has concluded that, if we want trees to do their "job" properly, we need to give them some space.
It seems that when people keep walking all over a tree’s personal space, the dirt gets compacted and becomes less porous, making it harder for the ground and the tree to sop up rain. The addition of simple fences can, in theory, prevent this from happening.
So it seems guerrilla gardeners who fence and manage a space around a tree have the right idea and the council contractors that are so fond of Tarmacking around a tree are most definitely not doing the tree or the street any favours.
Although this article looks at NYC, giving trees room to breathe surely applies to any urban environment.
Read more here: Give Trees Some Space
There are a number of these tiny gardens at the foot of trees in Crouch End. I think they need a bit of luck to survive the council's annual weed killing spree but I absolutely love them.
The NY bioswales need a bit of space and I'm not sure our pavements provide that, but there are ways of better replacing trees in the street with a technique called Structural Soil (basically something to grow in with a cage to take the weight above so it is not compressed) which, if the Wikipedia article is correct seems to be cheaper than topsoil. The cunning use of rock fragment to distribute the weight is so clever (if it really works) I'd love to see it implemented.
In the meanwhile we mustn't get too sentimental about trees, which do grow old and tired and need replacing. They are only human after all.
The message is, look after your local street trees! Clear grass etc from around the base, water in summer [a bucket every couple of weeks, especially young trees]. Cut off any stems sprouting from the ground [ Limes are especially prone to this]. Join the Tree Trust for Haringey or Haringey Tree Wardens. Need I say, the council hasn't got the resources anymore to do basic tree maintenance, so it's up to us!