In the UK "Ancient Woodland" means over 400 years old. There is no woodland in the UK that has been identified that has not been under active management by humans prior to this at some point. Manage your woods replant or support regeneration plant a mix of softwood to be treated and durable hard woods for carbon lockup and a mix of short rotation coppice for bio-fuels (wood chip), all of which can be integrated into a woodland management plan, provide a living for foresters.
Leaving Trees standing and un-managed would be detrimental to the environment in the UK at least.
Sadly there is a movement for woodburners to be installed in houses and HETAS approved KILN DRIED fire wood sold to suppy them. Shows the economy is still more powerful than common sense.