There is a fallacy about industrial afforestation capturing carbon dioxide. The evidence is that trees only become carbon positive at about 50 years of age and onwards, whereas a commercial crop is felled around 25-30 years and is hence carbon negative.
Any kind of forestry development has to show Biological Net Gain (NPF4 of UK and local regulations) and this proposed blanket forestry is not capable of doing this, because the area has a relatively high nature conservation interest already.