Mapping the Rainforests of Britain (atlasobscura.com)

I'll be honest I thought this was a "hot internet take" style comment but this comment is actually being generous. I'm quite honestly sure the block I grew up in and the one next to it had more trees and less development than whatever is left of that forest.

The word forest originally refers to land that is reserved for the king to hunt on, extract wood and other resources etc. from rather than a heavily wooded area. Even when it was first made a forest (and originally it was much larger) Nottingham forest wouldn't have been entirely, or even mostly closed canopy woodland. A lot of it would have been wooded pasture and heathland. Most of the wooded bits would have been managed by coppicing, polarding and selective felling, and then the forestry commission wiped out much of the rest in the post war period. There's a few bits of ancient woodland in there, but mostly in areas that would have been difficult to get to historically. For a laugh, google forest of Bowland, one of our larger forests that has and has never had more than a scattering if trees.

Pretty much all of the UK and Ireland has been cleared apart from scattered fragments of ancient woodland like this. Scotland lost almost all its trees by the 18th century. There are occasional bursts of panicking about timber being a strategic resource - oaks for shipbuilding, or more recently WW1 consumed timber for trench walls and props to such an extent that the Forestry Commission was established to grow it back.

The national forest I live next to here in Oregon is listed as being 6,462 km2...