Ancient woodland

Ancient woodland is the name used in the United Kingdom for woodland which has existed continuously since 1600 or before in England and Wales (or 1750 in Scotland). Before those dates, planting of new woodland was uncommon, so a wood present in 1600 was likely to have developed naturally. The American name for these forests is "old growth forest".
For many species of animal and plant, ancient woodland sites provide the only habitat. For many others, conditions on these sites are much more suitable than those on other sites. Ancient woodland in the UK, like rainforest in the tropics, is home to rare and threatened species, more than any other UK habitat. For these reasons ancient woodland is often described as an irreplaceable resource, or 'critical natural capital'.
Ancient woodland is formally defined on maps by Natural England and equivalent bodies. Many ancient woodlands have legal protection, but an ancient woodland is not automatically protected.