Loss of British woodland is mainly down to those pesky Europeans.
1000+ years ago trees covered around 15% of the landmass. The Norman French then took over as landlords. Once they and the Angevins had faded, the Tudors needed Navy warships to subdue the French and Spanish which took a huge toll on that figure; burning wood for fuel was also popular causing tree numbers to dwindle further until a C16th alternative was found - coal.
After WW1 woodland was down to 5%, prompting formation of the Forestry Commission and a remit to plant new forests. The subsequent century has seen UK woodland more than double to around 13% coverage, very nearly a return to pre-Norman levels.