And every 10 years, an area the size of Britain disappears under a jungle of concrete.
But it doesn't have to be like this.
Could it not be possible to build cities more in harmony with nature?
How, and whether we decide to invite the wildlife back, is up to us.
This tree is rising nearly 30 storeys.
It's one of almost 800 being planted to create a vertical forest in Milan.
This number of living trees would normally fill two hectares of woodland,
but here, they occupy one-tenth of that area.
Greening the walls and roofs of our buildings could create a rich and extensive habitat,
if we wanted it to do so.