By planting trees!
Sounds ridiculous but it works.
I saw it recently with a tree I planted myself.
The work being accomplished there under the guidance of landscape architect Christopher Cook is astonishing.
If you get to Melbourne, look him up and he'll be happy to show you.
It's just more evidence of what Andy Lipkis says:
"Trees are like acupuncture needles: the right tree in the right place can produce profound healing."